[PATCH v2] mmc: dw_mmc: Reset DMA before enabling IDMAC

On Fri, Oct 17, 2014 at 1:26 AM, Jaehoon Chung [off-list ref] wrote:

Hi, Sonny.

On 10/17/2014 01:58 AM, Sonny Rao wrote:

quoted

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.

Didn't affect the write throughput?

Write is usually much slower than read, but I went ahead and re-tested
and saw no difference on writes.

I tested this on exynos3/4 with DDR50 and HS200.

Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>

quoted

Signed-off-by: Sonny Rao <redacted>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
---
 drivers/mmc/host/dw_mmc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 69f0cc6..ca67f69 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 +449,10 @@ 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);
+     dw_mci_idmac_reset(host);
+
      /* Select IDMAC interface */
      temp = mci_readl(host, CTRL);
      temp |= SDMMC_CTRL_USE_IDMAC;