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authorNed Forrester <nforrester@whoi.edu>2008-09-13 02:33:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-09-13 14:41:52 -0700
commit7e96445533ac3f4f7964646a202ff3620602fab4 (patch)
tree8c8dfd18cb0447cabd834e2b68d209c2e870be24
parent8423597d676615f3dd2d9ab36f59f147086b90b8 (diff)
pxa2xx_spi: dma bugfixes
Fixes two DMA bugs in the pxa2xx_spi driver. The first bug is in all versions of this driver; the second was introduced in the 2.6.20 kernel, and prevents using the driver with chips like m25p16 flash (which can issue large DMA reads). 1. Zero length transfers are permitted for use to insert timing, but pxa2xx_spi.c will fail if this is requested in DMA mode. Fixed by using programmed I/O (PIO) mode for such transfers. 2. Transfers larger than 8191 are not permitted in DMA mode. A test for length rejects all large transfers regardless of DMA or PIO mode. Worked around by rejecting only large transfers with DMA mapped buffers, and forcing all other transfers larger than 8191 to use PIO mode. A rate limited warning is issued for DMA transfers forced to PIO mode. This patch should apply to all kernels back to and including 2.6.20; it was test patched against 2.6.20. An additional patch would be required for older kernels, but those versions are very buggy anyway. Signed-off-by: Ned Forrester <nforrester@whoi.edu> Cc: Vernon Sauder <vernoninhand@gmail.com> Cc: Eric Miao <eric.y.miao@gmail.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: <stable@kernel.org> [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/spi/pxa2xx_spi.c57
1 files changed, 43 insertions, 14 deletions
diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
index a7b9070e1b4..0e53354c1cf 100644
--- a/drivers/spi/pxa2xx_spi.c
+++ b/drivers/spi/pxa2xx_spi.c
@@ -47,9 +47,10 @@ MODULE_ALIAS("platform:pxa2xx-spi");
#define MAX_BUSES 3
-#define DMA_INT_MASK (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
-#define RESET_DMA_CHANNEL (DCSR_NODESC | DMA_INT_MASK)
-#define IS_DMA_ALIGNED(x) (((u32)(x)&0x07)==0)
+#define DMA_INT_MASK (DCSR_ENDINTR | DCSR_STARTINTR | DCSR_BUSERR)
+#define RESET_DMA_CHANNEL (DCSR_NODESC | DMA_INT_MASK)
+#define IS_DMA_ALIGNED(x) (((x) & 0x07) == 0)
+#define MAX_DMA_LEN 8191
/*
* for testing SSCR1 changes that require SSP restart, basically
@@ -887,14 +888,27 @@ static void pump_transfers(unsigned long data)
drv_data->cs_control(PXA2XX_CS_DEASSERT);
}
- /* Check transfer length */
- if (transfer->len > 8191)
- {
- dev_warn(&drv_data->pdev->dev, "pump_transfers: transfer "
- "length greater than 8191\n");
- message->status = -EINVAL;
- giveback(drv_data);
- return;
+ /* Check for transfers that need multiple DMA segments */
+ if (transfer->len > MAX_DMA_LEN && chip->enable_dma) {
+
+ /* reject already-mapped transfers; PIO won't always work */
+ if (message->is_dma_mapped
+ || transfer->rx_dma || transfer->tx_dma) {
+ dev_err(&drv_data->pdev->dev,
+ "pump_transfers: mapped transfer length "
+ "of %lu is greater than %d\n",
+ transfer->len, MAX_DMA_LEN);
+ message->status = -EINVAL;
+ giveback(drv_data);
+ return;
+ }
+
+ /* warn ... we force this to PIO mode */
+ if (printk_ratelimit())
+ dev_warn(&message->spi->dev, "pump_transfers: "
+ "DMA disabled for transfer length %ld "
+ "greater than %d\n",
+ (long)drv_data->len, MAX_DMA_LEN);
}
/* Setup the transfer state based on the type of transfer */
@@ -962,7 +976,7 @@ static void pump_transfers(unsigned long data)
&dma_thresh))
if (printk_ratelimit())
dev_warn(&message->spi->dev,
- "pump_transfer: "
+ "pump_transfers: "
"DMA burst size reduced to "
"match bits_per_word\n");
}
@@ -976,8 +990,23 @@ static void pump_transfers(unsigned long data)
message->state = RUNNING_STATE;
- /* Try to map dma buffer and do a dma transfer if successful */
- if ((drv_data->dma_mapped = map_dma_buffers(drv_data))) {
+ /* Try to map dma buffer and do a dma transfer if successful, but
+ * only if the length is non-zero and less than MAX_DMA_LEN.
+ *
+ * Zero-length non-descriptor DMA is illegal on PXA2xx; force use
+ * of PIO instead. Care is needed above because the transfer may
+ * have have been passed with buffers that are already dma mapped.
+ * A zero-length transfer in PIO mode will not try to write/read
+ * to/from the buffers
+ *
+ * REVISIT large transfers are exactly where we most want to be
+ * using DMA. If this happens much, split those transfers into
+ * multiple DMA segments rather than forcing PIO.
+ */
+ drv_data->dma_mapped = 0;
+ if (drv_data->len > 0 && drv_data->len <= MAX_DMA_LEN)
+ drv_data->dma_mapped = map_dma_buffers(drv_data);
+ if (drv_data->dma_mapped) {
/* Ensure we have the correct interrupt handler */
drv_data->transfer_handler = dma_transfer;