From b6018958a57f6621d6979c4384e42a3df636beed Mon Sep 17 00:00:00 2001 From: Cliff Brake Date: Thu, 22 Jan 2009 17:07:03 -0500 Subject: [PATCH] pxamci: enable DMA for write ops after CMD/RESP 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 Signed-off-by: Cliff Brake Acked-by: Eric Miao Signed-off-by: Pierre Ossman --- drivers/mmc/host/pxamci.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c index 3000422f4d8..9702ad3774c 100644 --- a/drivers/mmc/host/pxamci.c +++ b/drivers/mmc/host/pxamci.c @@ -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); } -- 2.41.1