Blackfin: TWI/I2C: implement bus speed get/set functions
While we're here, improve the speed calculation a bit to match the HRM. Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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@ -26,6 +26,7 @@
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#ifdef TWI0_CLKDIV
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#ifdef TWI0_CLKDIV
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#define bfin_write_TWI_CLKDIV(val) bfin_write_TWI0_CLKDIV(val)
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#define bfin_write_TWI_CLKDIV(val) bfin_write_TWI0_CLKDIV(val)
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#define bfin_read_TWI_CLKDIV(val) bfin_read_TWI0_CLKDIV(val)
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#define bfin_write_TWI_CONTROL(val) bfin_write_TWI0_CONTROL(val)
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#define bfin_write_TWI_CONTROL(val) bfin_write_TWI0_CONTROL(val)
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#define bfin_read_TWI_CONTROL(val) bfin_read_TWI0_CONTROL(val)
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#define bfin_read_TWI_CONTROL(val) bfin_read_TWI0_CONTROL(val)
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#define bfin_write_TWI_MASTER_ADDR(val) bfin_write_TWI0_MASTER_ADDR(val)
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#define bfin_write_TWI_MASTER_ADDR(val) bfin_write_TWI0_MASTER_ADDR(val)
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@ -44,8 +45,21 @@
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#ifdef CONFIG_TWICLK_KHZ
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#ifdef CONFIG_TWICLK_KHZ
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# error do not define CONFIG_TWICLK_KHZ ... use CONFIG_SYS_I2C_SPEED
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# error do not define CONFIG_TWICLK_KHZ ... use CONFIG_SYS_I2C_SPEED
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#endif
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#endif
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#if CONFIG_SYS_I2C_SPEED > 400000
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# error The Blackfin I2C hardware can only operate at 400KHz max
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/*
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* The way speed is changed into duty often results in integer truncation
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* with 50% duty, so we'll force rounding up to the next duty by adding 1
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* to the max. In practice this will get us a speed of something like
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* 385 KHz. The other limit is easy to handle as it is only 8 bits.
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*/
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#define I2C_SPEED_MAX 400000
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#define I2C_SPEED_TO_DUTY(speed) (5000000 / (speed))
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#define I2C_DUTY_MAX (I2C_SPEED_TO_DUTY(I2C_SPEED_MAX) + 1)
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#define I2C_DUTY_MIN 0xff /* 8 bit limited */
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#define SYS_I2C_DUTY I2C_SPEED_TO_DUTY(CONFIG_SYS_I2C_SPEED)
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/* Note: duty is inverse of speed, so the comparisons below are correct */
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#if SYS_I2C_DUTY < I2C_DUTY_MAX || SYS_I2C_DUTY > I2C_DUTY_MIN
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# error "The Blackfin I2C hardware can only operate 20KHz - 400KHz"
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#endif
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#endif
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/* All transfers are described by this data structure */
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/* All transfers are described by this data structure */
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@ -213,7 +227,36 @@ static int i2c_transfer(uchar chip, uint addr, int alen, uchar *buffer, int len,
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return ret;
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return ret;
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}
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}
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/*
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/**
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* i2c_set_bus_speed - set i2c bus speed
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* @speed: bus speed (in HZ)
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*/
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int i2c_set_bus_speed(unsigned int speed)
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{
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u16 clkdiv = I2C_SPEED_TO_DUTY(speed);
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/* Set TWI interface clock */
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if (clkdiv < I2C_DUTY_MAX || clkdiv > I2C_DUTY_MIN)
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return -1;
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bfin_write_TWI_CLKDIV((clkdiv << 8) | (clkdiv & 0xff));
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/* Don't turn it on */
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bfin_write_TWI_MASTER_CTL(speed > 100000 ? FAST : 0);
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return 0;
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}
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/**
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* i2c_get_bus_speed - get i2c bus speed
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* @speed: bus speed (in HZ)
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*/
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unsigned int i2c_get_bus_speed(void)
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{
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/* 10 MHz / (2 * CLKDIV) -> 5 MHz / CLKDIV */
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return 5000000 / (bfin_read_TWI_CLKDIV() & 0xff);
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}
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/**
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* i2c_init - initialize the i2c bus
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* i2c_init - initialize the i2c bus
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* @speed: bus speed (in HZ)
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* @speed: bus speed (in HZ)
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* @slaveaddr: address of device in slave mode (0 - not slave)
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* @slaveaddr: address of device in slave mode (0 - not slave)
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@ -229,15 +272,9 @@ void i2c_init(int speed, int slaveaddr)
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bfin_write_TWI_CONTROL(prescale);
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bfin_write_TWI_CONTROL(prescale);
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/* Set TWI interface clock as specified */
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/* Set TWI interface clock as specified */
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bfin_write_TWI_CLKDIV(
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i2c_set_bus_speed(speed);
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((5 * 1024 / (speed / 1000)) << 8) |
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((5 * 1024 / (speed / 1000)) & 0xFF)
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);
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/* Don't turn it on */
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/* Enable it */
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bfin_write_TWI_MASTER_CTL(speed > 100000 ? FAST : 0);
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/* But enable it */
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bfin_write_TWI_CONTROL(TWI_ENA | prescale);
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bfin_write_TWI_CONTROL(TWI_ENA | prescale);
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SSYNC();
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SSYNC();
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