[PATCH] mmc: dw_mmc: Reset DMA before enabling IDMAC
From: Alim Akhtar <hidden>
Date: 2014-10-08 11:29:16
Also in:
linux-mmc, lkml
Hi Sonny/Doug, On Mon, Oct 6, 2014 at 11:23 PM, Sonny Rao [off-list ref] wrote:
quoted hunk ↗ jump to hunk
We've already got a reset of DMA after it's done. Add one before we start DMA too. This fixes a data corruption on Rockchip SoCs which will get bad data when doing a DMA transfer after doing a PIO transfer. We tested this on an Exynos 5800 with HS200 and didn't notice any difference in sequential read throughput. Signed-off-by: Sonny Rao <redacted> Signed-off-by: Doug Anderson <dianders@chromium.org> --- drivers/mmc/host/dw_mmc.c | 4 ++++ 1 file changed, 4 insertions(+)diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c index 69f0cc6..2b5401e 100644 --- a/drivers/mmc/host/dw_mmc.c +++ b/drivers/mmc/host/dw_mmc.c@@ -83,6 +83,7 @@ struct idmac_desc { #endif /* CONFIG_MMC_DW_IDMAC */ static bool dw_mci_reset(struct dw_mci *host); +static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset); #if defined(CONFIG_DEBUG_FS) static int dw_mci_req_show(struct seq_file *s, void *v)@@ -448,6 +449,9 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len) dw_mci_translate_sglist(host, host->data, sg_len); + /* Make sure to reset DMA in case we did PIO before this */ + dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET); +
Though this is good to do, but this does not look complete to me. dw_mmc data book does mention that " It is recommended that the host issue reset to DMA interface by setting DMA_RESET bit of the CTRL register and then issue a IDMAC software reset." The above lines are from 'Transmission and reception with internal DMA' section of the data book. My suggestion here to add dw_mci_idmac_reset() call after this above change. What is the controller version used in your case?
/* Select IDMAC interface */
temp = mci_readl(host, CTRL);
temp |= SDMMC_CTRL_USE_IDMAC;
--
1.8.3.2
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html-- Regards, Alim