diff options
| author | Philipp Zabel <philipp.zabel@gmail.com> | 2008-07-06 01:15:34 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-06 10:37:40 -0700 |
| commit | 97f8571e663c808ad2d01a396627235167291556 (patch) | |
| tree | 2e189714b2355996dba8974642460580077d3c0e /drivers | |
| parent | 09ca8adbe9f724a7e96f512c0039c4c4a1c5dcc0 (diff) | |
pxamci: fix byte aligned DMA transfers
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>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/mmc/host/pxamci.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c index 65210fca37ed..d89475d36988 100644 --- a/drivers/mmc/host/pxamci.c +++ b/drivers/mmc/host/pxamci.c @@ -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; } |