From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ned Forrester Subject: [patch 2.6.26 and earlier] pxa2xx_spi: bugfix full duplex dma data corruption Date: Thu, 20 Nov 2008 17:56:38 -0500 Message-ID: <4925EB26.7080604@whoi.edu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: spi-devel , Vernon Sauder , "J. Scott Merritt" , Stephen Street To: David Brownell Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org From: Ned Forrester Fixes a data corruption bug in pxa2xx_spi.c when operating in full duplex mode with DMA and using buffers that overlap. SPI transmit and receive buffers are allowed to be the same or to overlap. However, this driver fails if such overlap is attempted in DMA mode because it maps the rx and tx buffers in the wrong order. By mapping DMA_FROM_DEVICE (read) before DMA_TO_DEVICE (write), it invalidates the cache before flushing it, thus discarding data which should have been transmitted. The patch corrects the order of mapping. This bug exists in all versions of pxa2xx_spi.c; similar bugs are in the drivers for two other SPI controllers (au1500, imx). This patch has been tested on kernel 2.6.20 using verification of loopback data with: random transfer length, random bits-per-word, random positive offsets (both larger and smaller than transfer length) between the start of the rx and tx buffers, and varying clock rates. This patch applies to all kernels from 2.6.17 t 2.6.26. Signed-off-by: Ned Forrester Cc: Vernon Sauder Cc: J. Scott Merritt Cc: Stephen Street --- drivers/spi/pxa2xx_spi.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff -Nurp linux-2.6.20/drivers/spi/pxa2xx_spi.c linux-2.6.20_dma_overlap_patch/drivers/spi/pxa2xx_spi.c --- linux-2.6.20/drivers/spi/pxa2xx_spi.c 2007-02-04 18:44:54.000000000 +0000 +++ linux-2.6.20_dma_overlap_patch/drivers/spi/pxa2xx_spi.c 2008-11-17 18:21:57.000000000 +0000 @@ -334,21 +334,21 @@ static int map_dma_buffers(struct driver } else drv_data->tx_map_len = drv_data->len; - /* Stream map the rx buffer */ - drv_data->rx_dma = dma_map_single(dev, drv_data->rx, - drv_data->rx_map_len, - DMA_FROM_DEVICE); - if (dma_mapping_error(drv_data->rx_dma)) - return 0; - - /* Stream map the tx buffer */ + /* Stream map the tx buffer. Always do DMA_TO_DEVICE first + * so we flush the cache *before* invalidating it, in case + * the tx and rx buffers overlap. + */ drv_data->tx_dma = dma_map_single(dev, drv_data->tx, - drv_data->tx_map_len, - DMA_TO_DEVICE); + drv_data->tx_map_len, DMA_TO_DEVICE); + if (dma_mapping_error(drv_data->tx_dma)) + return 0; - if (dma_mapping_error(drv_data->tx_dma)) { - dma_unmap_single(dev, drv_data->rx_dma, + /* Stream map the rx buffer */ + drv_data->rx_dma = dma_map_single(dev, drv_data->rx, drv_data->rx_map_len, DMA_FROM_DEVICE); + if (dma_mapping_error(drv_data->rx_dma)) { + dma_unmap_single(dev, drv_data->tx_dma, + drv_data->tx_map_len, DMA_TO_DEVICE); return 0; } -- ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/