From 75b53aee2f4fe6375c6007226bf68d75b5c4a929 Mon Sep 17 00:00:00 2001 From: Paul Walmsley Date: Fri, 24 Aug 2012 06:00:18 +0000 Subject: [PATCH] mmc: omap: fix broken PIO mode After commit 26b88520b80695a6fa5fd95b5d97c03f4daf87e0 ("mmc: omap_hsmmc: remove private DMA API implementation"), the Nokia N800 here stopped booting: [ 2.086181] Waiting for root device /dev/mmcblk0p1... [ 2.324066] Unhandled fault: imprecise external abort (0x406) at 0x00000000 [ 2.331451] Internal error: : 406 [#1] ARM [ 2.335784] Modules linked in: [ 2.339050] CPU: 0 Not tainted (3.6.0-rc3 #60) [ 2.344146] PC is at default_idle+0x28/0x30 [ 2.348602] LR is at trace_hardirqs_on_caller+0x15c/0x1b0 ... This turned out to be due to memory corruption caused by long-broken PIO code in drivers/mmc/host/omap.c. (Previously, this driver had been using DMA; but the above commit caused the MMC driver to fall back to PIO mode with an unmodified Kconfig.) The PIO code, added with the rest of the driver in commit 730c9b7e6630f786fcec026fb11d2e6f2c90fdcb ("[MMC] Add OMAP MMC host driver"), confused bytes with 16-bit words. This bug caused memory located after the PIO transfer buffer to be corrupted with transfers larger than 32 bytes. The driver also did not increment the buffer pointer after the transfer occurred. This bug resulted in data corruption during any transfer larger than 64 bytes. Signed-off-by: Paul Walmsley Reviewed-by: Felipe Balbi Tested-by: Tony Lindgren Signed-off-by: Chris Ball --- drivers/mmc/host/omap.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c index 50e08f03aa6..a5999a74496 100644 --- a/drivers/mmc/host/omap.c +++ b/drivers/mmc/host/omap.c @@ -668,7 +668,7 @@ mmc_omap_clk_timer(unsigned long data) static void mmc_omap_xfer_data(struct mmc_omap_host *host, int write) { - int n; + int n, nwords; if (host->buffer_bytes_left == 0) { host->sg_idx++; @@ -678,15 +678,23 @@ mmc_omap_xfer_data(struct mmc_omap_host *host, int write) n = 64; if (n > host->buffer_bytes_left) n = host->buffer_bytes_left; + + nwords = n / 2; + nwords += n & 1; /* handle odd number of bytes to transfer */ + host->buffer_bytes_left -= n; host->total_bytes_left -= n; host->data->bytes_xfered += n; if (write) { - __raw_writesw(host->virt_base + OMAP_MMC_REG(host, DATA), host->buffer, n); + __raw_writesw(host->virt_base + OMAP_MMC_REG(host, DATA), + host->buffer, nwords); } else { - __raw_readsw(host->virt_base + OMAP_MMC_REG(host, DATA), host->buffer, n); + __raw_readsw(host->virt_base + OMAP_MMC_REG(host, DATA), + host->buffer, nwords); } + + host->buffer += nwords; } static inline void mmc_omap_report_irq(u16 status)