spi_lm70llp parport adapter driver
This adds a driver for the LM70-LLP parport adapter, which is an eval board for the LM70 temperature sensor. For those without that board, it may be a simpler example of a parport-to-SPI adapter then spi_butterfly. Signed-off-by: Kaiwan N Billimoria <kaiwan@designergraphix.com> Doc, coding style, and interface updates; build fixes. Minor rename. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kaiwan N Billimoria
Linus Torvalds
parent
4917d92780
commit
78961a5740
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@ -0,0 +1,69 @@
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spi_lm70llp : LM70-LLP parport-to-SPI adapter
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==============================================
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Supported board/chip:
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* National Semiconductor LM70 LLP evaluation board
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Datasheet: http://www.national.com/pf/LM/LM70.html
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Author:
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Kaiwan N Billimoria <kaiwan@designergraphix.com>
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Description
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-----------
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This driver provides glue code connecting a National Semiconductor LM70 LLP
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temperature sensor evaluation board to the kernel's SPI core subsystem.
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In effect, this driver turns the parallel port interface on the eval board
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into a SPI bus with a single device, which will be driven by the generic
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LM70 driver (drivers/hwmon/lm70.c).
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The hardware interfacing on the LM70 LLP eval board is as follows:
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Parallel LM70 LLP
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Port Direction JP2 Header
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----------- --------- ----------------
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D0 2 - -
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D1 3 --> V+ 5
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D2 4 --> V+ 5
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D3 5 --> V+ 5
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D4 6 --> V+ 5
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D5 7 --> nCS 8
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D6 8 --> SCLK 3
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D7 9 --> SI/O 5
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GND 25 - GND 7
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Select 13 <-- SI/O 1
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----------- --------- ----------------
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Note that since the LM70 uses a "3-wire" variant of SPI, the SI/SO pin
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is connected to both pin D7 (as Master Out) and Select (as Master In)
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using an arrangment that lets either the parport or the LM70 pull the
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pin low. This can't be shared with true SPI devices, but other 3-wire
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devices might share the same SI/SO pin.
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The bitbanger routine in this driver (lm70_txrx) is called back from
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the bound "hwmon/lm70" protocol driver through its sysfs hook, using a
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spi_write_then_read() call. It performs Mode 0 (SPI/Microwire) bitbanging.
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The lm70 driver then inteprets the resulting digital temperature value
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and exports it through sysfs.
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A "gotcha": National Semiconductor's LM70 LLP eval board circuit schematic
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shows that the SI/O line from the LM70 chip is connected to the base of a
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transistor Q1 (and also a pullup, and a zener diode to D7); while the
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collector is tied to VCC.
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Interpreting this circuit, when the LM70 SI/O line is High (or tristate
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and not grounded by the host via D7), the transistor conducts and switches
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the collector to zero, which is reflected on pin 13 of the DB25 parport
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connector. When SI/O is Low (driven by the LM70 or the host) on the other
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hand, the transistor is cut off and the voltage tied to it's collector is
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reflected on pin 13 as a High level.
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So: the getmiso inline routine in this driver takes this fact into account,
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inverting the value read at pin 13.
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Thanks to
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---------
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o David Brownell for mentoring the SPI-side driver development.
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o Dr.Craig Hollabaugh for the (early) "manual" bitbanging driver version.
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o Nadir Billimoria for help interpreting the circuit schematic.
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@ -107,6 +107,15 @@ config SPI_IMX
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This enables using the Freescale iMX SPI controller in master
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mode.
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config SPI_LM70_LLP
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tristate "Parallel port adapter for LM70 eval board (DEVELOPMENT)"
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depends on SPI_MASTER && PARPORT && EXPERIMENTAL
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select SPI_BITBANG
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help
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This driver supports the NS LM70 LLP Evaluation Board,
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which interfaces to an LM70 temperature sensor using
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a parallel port.
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config SPI_MPC52xx_PSC
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tristate "Freescale MPC52xx PSC SPI controller"
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depends on SPI_MASTER && PPC_MPC52xx && EXPERIMENTAL
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@ -17,6 +17,7 @@ obj-$(CONFIG_SPI_BITBANG) += spi_bitbang.o
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obj-$(CONFIG_SPI_AU1550) += au1550_spi.o
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obj-$(CONFIG_SPI_BUTTERFLY) += spi_butterfly.o
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obj-$(CONFIG_SPI_IMX) += spi_imx.o
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obj-$(CONFIG_SPI_LM70_LLP) += spi_lm70llp.o
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obj-$(CONFIG_SPI_PXA2XX) += pxa2xx_spi.o
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obj-$(CONFIG_SPI_OMAP_UWIRE) += omap_uwire.o
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obj-$(CONFIG_SPI_MPC52xx_PSC) += mpc52xx_psc_spi.o
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@ -0,0 +1,361 @@
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/*
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* spi_lm70llp.c - driver for lm70llp eval board for the LM70 sensor
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*
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* Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/parport.h>
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#include <linux/sysfs.h>
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#include <linux/workqueue.h>
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#include <linux/spi/spi.h>
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#include <linux/spi/spi_bitbang.h>
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/*
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* The LM70 communicates with a host processor using a 3-wire variant of
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* the SPI/Microwire bus interface. This driver specifically supports an
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* NS LM70 LLP Evaluation Board, interfacing to a PC using its parallel
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* port to bitbang an SPI-parport bridge. Accordingly, this is an SPI
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* master controller driver. The hwmon/lm70 driver is a "SPI protocol
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* driver", layered on top of this one and usable without the lm70llp.
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*
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* The LM70 is a temperature sensor chip from National Semiconductor; its
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* datasheet is available at http://www.national.com/pf/LM/LM70.html
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*
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* Also see Documentation/spi/spi-lm70llp. The SPI<->parport code here is
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* (heavily) based on spi-butterfly by David Brownell.
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*
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* The LM70 LLP connects to the PC parallel port in the following manner:
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*
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* Parallel LM70 LLP
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* Port Direction JP2 Header
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* ----------- --------- ------------
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* D0 2 - -
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* D1 3 --> V+ 5
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* D2 4 --> V+ 5
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* D3 5 --> V+ 5
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* D4 6 --> V+ 5
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* D5 7 --> nCS 8
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* D6 8 --> SCLK 3
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* D7 9 --> SI/O 5
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* GND 25 - GND 7
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* Select 13 <-- SI/O 1
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*
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* Note that parport pin 13 actually gets inverted by the transistor
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* arrangement which lets either the parport or the LM70 drive the
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* SI/SO signal.
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*/
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#define DRVNAME "spi-lm70llp"
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#define lm70_INIT 0xBE
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#define SIO 0x10
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#define nCS 0x20
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#define SCLK 0x40
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/*-------------------------------------------------------------------------*/
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struct spi_lm70llp {
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struct spi_bitbang bitbang;
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struct parport *port;
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struct pardevice *pd;
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struct spi_device *spidev_lm70;
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struct spi_board_info info;
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struct class_device *cdev;
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};
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/* REVISIT : ugly global ; provides "exclusive open" facility */
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static struct spi_lm70llp *lm70llp;
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/*-------------------------------------------------------------------*/
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static inline struct spi_lm70llp *spidev_to_pp(struct spi_device *spi)
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{
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return spi->controller_data;
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}
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/*---------------------- LM70 LLP eval board-specific inlines follow */
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/* NOTE: we don't actually need to reread the output values, since they'll
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* still be what we wrote before. Plus, going through parport builds in
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* a ~1ms/operation delay; these SPI transfers could easily be faster.
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*/
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static inline void deassertCS(struct spi_lm70llp *pp)
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{
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u8 data = parport_read_data(pp->port);
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parport_write_data(pp->port, data | nCS);
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}
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static inline void assertCS(struct spi_lm70llp *pp)
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{
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u8 data = parport_read_data(pp->port);
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parport_write_data(pp->port, data & ~nCS);
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}
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static inline void clkHigh(struct spi_lm70llp *pp)
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{
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u8 data = parport_read_data(pp->port);
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parport_write_data(pp->port, data | SCLK);
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}
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static inline void clkLow(struct spi_lm70llp *pp)
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{
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u8 data = parport_read_data(pp->port);
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parport_write_data(pp->port, data & ~SCLK);
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}
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/*------------------------- SPI-LM70-specific inlines ----------------------*/
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static inline void spidelay(unsigned d)
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{
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udelay(d);
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}
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static inline void setsck(struct spi_device *s, int is_on)
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{
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struct spi_lm70llp *pp = spidev_to_pp(s);
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if (is_on)
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clkHigh(pp);
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else
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clkLow(pp);
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}
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static inline void setmosi(struct spi_device *s, int is_on)
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{
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/* FIXME update D7 ... this way we can put the chip
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* into shutdown mode and read the manufacturer ID,
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* but we can't put it back into operational mode.
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*/
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}
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/*
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* getmiso:
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* Why do we return 0 when the SIO line is high and vice-versa?
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* The fact is, the lm70 eval board from NS (which this driver drives),
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* is wired in just such a way : when the lm70's SIO goes high, a transistor
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* switches it to low reflecting this on the parport (pin 13), and vice-versa.
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*/
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static inline int getmiso(struct spi_device *s)
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{
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struct spi_lm70llp *pp = spidev_to_pp(s);
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return ((SIO == (parport_read_status(pp->port) & SIO)) ? 0 : 1 );
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}
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/*--------------------------------------------------------------------*/
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#define EXPAND_BITBANG_TXRX 1
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#include <linux/spi/spi_bitbang.h>
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static void lm70_chipselect(struct spi_device *spi, int value)
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{
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struct spi_lm70llp *pp = spidev_to_pp(spi);
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if (value)
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assertCS(pp);
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else
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deassertCS(pp);
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}
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/*
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* Our actual bitbanger routine.
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*/
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static u32 lm70_txrx(struct spi_device *spi, unsigned nsecs, u32 word, u8 bits)
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{
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static u32 sio=0;
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static int first_time=1;
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/* First time: perform SPI bitbang and return the LSB of
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* the result of the SPI call.
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*/
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if (first_time) {
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sio = bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
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first_time=0;
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return (sio & 0x00ff);
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}
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/* Return the MSB of the result of the SPI call */
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else {
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first_time=1;
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return (sio >> 8);
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}
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}
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static void spi_lm70llp_attach(struct parport *p)
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{
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struct pardevice *pd;
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struct spi_lm70llp *pp;
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struct spi_master *master;
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int status;
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if (lm70llp) {
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printk(KERN_WARNING
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"%s: spi_lm70llp instance already loaded. Aborting.\n",
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DRVNAME);
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return;
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}
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/* TODO: this just _assumes_ a lm70 is there ... no probe;
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* the lm70 driver could verify it, reading the manf ID.
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*/
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master = spi_alloc_master(p->physport->dev, sizeof *pp);
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if (!master) {
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status = -ENOMEM;
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goto out_fail;
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}
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pp = spi_master_get_devdata(master);
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master->bus_num = -1; /* dynamic alloc of a bus number */
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master->num_chipselect = 1;
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/*
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* SPI and bitbang hookup.
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*/
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pp->bitbang.master = spi_master_get(master);
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pp->bitbang.chipselect = lm70_chipselect;
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pp->bitbang.txrx_word[SPI_MODE_0] = lm70_txrx;
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pp->bitbang.flags = SPI_3WIRE;
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/*
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* Parport hookup
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*/
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pp->port = p;
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pd = parport_register_device(p, DRVNAME,
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NULL, NULL, NULL,
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PARPORT_FLAG_EXCL, pp);
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if (!pd) {
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status = -ENOMEM;
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goto out_free_master;
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}
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pp->pd = pd;
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status = parport_claim(pd);
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if (status < 0)
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goto out_parport_unreg;
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/*
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* Start SPI ...
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*/
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status = spi_bitbang_start(&pp->bitbang);
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if (status < 0) {
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printk(KERN_WARNING
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"%s: spi_bitbang_start failed with status %d\n",
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DRVNAME, status);
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goto out_off_and_release;
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}
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/*
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* The modalias name MUST match the device_driver name
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* for the bus glue code to match and subsequently bind them.
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* We are binding to the generic drivers/hwmon/lm70.c device
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* driver.
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*/
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strcpy(pp->info.modalias, "lm70");
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pp->info.max_speed_hz = 6 * 1000 * 1000;
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pp->info.chip_select = 0;
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pp->info.mode = SPI_3WIRE | SPI_MODE_0;
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/* power up the chip, and let the LM70 control SI/SO */
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parport_write_data(pp->port, lm70_INIT);
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/* Enable access to our primary data structure via
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* the board info's (void *)controller_data.
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*/
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pp->info.controller_data = pp;
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pp->spidev_lm70 = spi_new_device(pp->bitbang.master, &pp->info);
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if (pp->spidev_lm70)
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dev_dbg(&pp->spidev_lm70->dev, "spidev_lm70 at %s\n",
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pp->spidev_lm70->dev.bus_id);
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else {
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printk(KERN_WARNING "%s: spi_new_device failed\n", DRVNAME);
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status = -ENODEV;
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goto out_bitbang_stop;
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}
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pp->spidev_lm70->bits_per_word = 16;
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lm70llp = pp;
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return;
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out_bitbang_stop:
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spi_bitbang_stop(&pp->bitbang);
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out_off_and_release:
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/* power down */
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parport_write_data(pp->port, 0);
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mdelay(10);
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parport_release(pp->pd);
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out_parport_unreg:
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parport_unregister_device(pd);
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out_free_master:
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(void) spi_master_put(master);
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out_fail:
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pr_info("%s: spi_lm70llp probe fail, status %d\n", DRVNAME, status);
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}
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static void spi_lm70llp_detach(struct parport *p)
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{
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struct spi_lm70llp *pp;
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if (!lm70llp || lm70llp->port != p)
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return;
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pp = lm70llp;
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spi_bitbang_stop(&pp->bitbang);
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/* power down */
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parport_write_data(pp->port, 0);
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msleep(10);
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parport_release(pp->pd);
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parport_unregister_device(pp->pd);
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(void) spi_master_put(pp->bitbang.master);
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lm70llp = NULL;
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}
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static struct parport_driver spi_lm70llp_drv = {
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.name = DRVNAME,
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.attach = spi_lm70llp_attach,
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.detach = spi_lm70llp_detach,
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};
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static int __init init_spi_lm70llp(void)
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{
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return parport_register_driver(&spi_lm70llp_drv);
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}
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module_init(init_spi_lm70llp);
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static void __exit cleanup_spi_lm70llp(void)
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{
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parport_unregister_driver(&spi_lm70llp_drv);
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}
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module_exit(cleanup_spi_lm70llp);
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MODULE_AUTHOR("Kaiwan N Billimoria <kaiwan@designergraphix.com>");
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MODULE_DESCRIPTION(
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"Parport adapter for the National Semiconductor LM70 LLP eval board");
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MODULE_LICENSE("GPL");
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