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pxamci: fix byte aligned DMA transfers

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The pxa27x DMA controller defaults to 64-bit alignment. This caused
the SCR reads to fail (and, depending on card type, error out) when
card->raw_scr was not aligned on a 8-byte boundary.

For performance reasons all scatter-gather addresses passed to
pxamci_request should be aligned on 8-byte boundaries, but if
this can't be guaranteed, byte aligned DMA transfers in the
have to be enabled in the controller to get correct behaviour.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Philipp Zabel 2008-07-06 01:15:34 +02:00 committed by Linus Torvalds
parent 09ca8adbe9
commit 97f8571e66
1 changed files with 13 additions and 0 deletions
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13
drivers/mmc/host/pxamci.c
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@ -114,6 +114,7 @@ static void pxamci_setup_data(struct pxamci_host *host, struct mmc_data *data)
unsigned int nob = data->blocks;
unsigned long long clks;
unsigned int timeout;
bool dalgn = 0;
u32 dcmd;
int i;
@ -152,6 +153,9 @@ static void pxamci_setup_data(struct pxamci_host *host, struct mmc_data *data)
host->sg_cpu[i].dcmd = dcmd | length;
if (length & 31 && !(data->flags & MMC_DATA_READ))
host->sg_cpu[i].dcmd |= DCMD_ENDIRQEN;
/* Not aligned to 8-byte boundary? */
if (sg_dma_address(&data->sg[i]) & 0x7)
dalgn = 1;
if (data->flags & MMC_DATA_READ) {
host->sg_cpu[i].dsadr = host->res->start + MMC_RXFIFO;
host->sg_cpu[i].dtadr = sg_dma_address(&data->sg[i]);
@ -165,6 +169,15 @@ static void pxamci_setup_data(struct pxamci_host *host, struct mmc_data *data)
host->sg_cpu[host->dma_len - 1].ddadr = DDADR_STOP;
wmb();
/*
* The PXA27x DMA controller encounters overhead when working with
* unaligned (to 8-byte boundaries) data, so switch on byte alignment
* mode only if we have unaligned data.
*/
if (dalgn)
DALGN |= (1 << host->dma);
else
DALGN &= (1 << host->dma);
DDADR(host->dma) = host->sg_dma;
DCSR(host->dma) = DCSR_RUN;
}