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pxamci: enable DMA for write ops after CMD/RESP

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With the PXA270 MMC hardware, there seems to be an issue of
data corruption on writes where a 4KB data block is offset
by one byte.

If we delay enabling the DMA for writes until after the CMD/RESP
has finished, the problem seems to be fixed.

related to PXA270 Erratum #91

Tested-by: Vernon Sauder <VernonInHand@gmail.com>
Signed-off-by: Cliff Brake <cbrake@bec-systems.com>
Acked-by: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
This commit is contained in:
Cliff Brake 2009-01-22 17:07:03 -05:00 committed by Pierre Ossman
parent e10a854c46
commit b6018958a5
1 changed files with 15 additions and 1 deletions
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16
drivers/mmc/host/pxamci.c
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@ -180,7 +180,15 @@ static void pxamci_setup_data(struct pxamci_host *host, struct mmc_data *data)
else
DALGN &= ~(1 << host->dma);
DDADR(host->dma) = host->sg_dma;
DCSR(host->dma) = DCSR_RUN;
/*
* workaround for erratum #91:
* only start DMA now if we are doing a read,
* otherwise we wait until CMD/RESP has finished
* before starting DMA.
*/
if (!cpu_is_pxa27x() || data->flags & MMC_DATA_READ)
DCSR(host->dma) = DCSR_RUN;
}
static void pxamci_start_cmd(struct pxamci_host *host, struct mmc_command *cmd, unsigned int cmdat)
@ -267,6 +275,12 @@ static int pxamci_cmd_done(struct pxamci_host *host, unsigned int stat)
pxamci_disable_irq(host, END_CMD_RES);
if (host->data && !cmd->error) {
pxamci_enable_irq(host, DATA_TRAN_DONE);
/*
* workaround for erratum #91, if doing write
* enable DMA late
*/
if (cpu_is_pxa27x() && host->data->flags & MMC_DATA_WRITE)
DCSR(host->dma) = DCSR_RUN;
} else {
pxamci_finish_request(host, host->mrq);
}