From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ned Forrester Subject: [patch 2.6.28-rc4] spi: pxa2xx_spi.c fix DMA mapping sequence Date: Sat, 15 Nov 2008 16:16:10 -0500 Message-ID: <491F3C1A.1030402@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" 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 bug in pxa2xx_spi.c when operating in direct memory access (DMA) mode. The transmit and receive buffers are allowed to be the same or to overlap, but pxa2xx_spi.c fails if this is attempted in DMA mode because it performs mapping of the rx and tx buffers in the wrong order. By mapping DMA_FROM_DEVICE before DMA_TO_DEVICE, it invalidates the cache before flushing it. The patch corrects the order of mapping. This bug exists in all versions of pxa2xx_spi.c A version of 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 kernels 2.6.27 and 2.6.28. A separate patch is required for 2.6.20 through 2.6.26. Signed-off-by: Ned Forrester Cc: Vernon Sauder Cc: J. Scott Merritt --- drivers/spi/pxa2xx_spi.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) diff -Nurp linux-2.6.28-rc4/drivers/spi/pxa2xx_spi.c linux-2.6.28-rc4_dma_overlap_patch/drivers/spi/pxa2xx_spi.c --- linux-2.6.28-rc4/drivers/spi/pxa2xx_spi.c 2008-11-13 13:59:03.000000000 +0000 +++ linux-2.6.28-rc4_dma_overlap_patch/drivers/spi/pxa2xx_spi.c 2008-11-15 17:25:36.000000000 +0000 @@ -352,21 +352,20 @@ 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(dev, drv_data->rx_dma)) - return 0; - - /* Stream map the tx buffer */ + /* Stream map the tx buffer. Always do DMA_TO_DEVICE first, + * because we want to 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(dev, drv_data->tx_dma)) + return 0; - if (dma_mapping_error(dev, 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(dev, drv_data->rx_dma)) { + dma_unmap_single(dev, drv_data->tx_dma, + drv_data->tx_map_len, DMA_TO_DEVICE); return 0; } -- Ned Forrester nforrester-/d+BM93fTQY@public.gmane.org Oceanographic Systems Lab 508-289-2226 Applied Ocean Physics and Engineering Dept. Woods Hole Oceanographic Institution Woods Hole, MA 02543, USA http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212 http://www.whoi.edu/hpb/Site.do?id=1532 http://www.whoi.edu/page.do?pid=10079 ------------------------------------------------------------------------- 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=/