* [patch 2.6.28-rc4] spi: pxa2xx_spi.c fix DMA mapping sequence
@ 2008-11-15 21:16 Ned Forrester
[not found] ` <491F3C1A.1030402-/d+BM93fTQY@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Ned Forrester @ 2008-11-15 21:16 UTC (permalink / raw)
To: David Brownell; +Cc: spi-devel, Vernon Sauder, J. Scott Merritt
From: Ned Forrester <nforrester-/d+BM93fTQY@public.gmane.org>
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 <nforrester-/d+BM93fTQY@public.gmane.org>
Cc: Vernon Sauder <vernoninhand-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: J. Scott Merritt <merrij3-IL7dBOYR4Vg@public.gmane.org>
---
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
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2008-11-15 21:16 [patch 2.6.28-rc4] spi: pxa2xx_spi.c fix DMA mapping sequence Ned Forrester
[not found] ` <491F3C1A.1030402-/d+BM93fTQY@public.gmane.org>
2008-11-15 21:21 ` Ned Forrester
[not found] ` <491F3D4E.8080502-/d+BM93fTQY@public.gmane.org>
2008-11-15 22:09 ` David Brownell
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