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

From: Doug Anderson
Date: Thu Oct 09 2014 - 20:36:42 EST


On Thu, Oct 9, 2014 at 3:19 PM, Alim Akhtar <alim.akhtar@xxxxxxxxx> wrote:
> Thats fine, I think every vendor (most of them) has a custom
> implementation of dw_mmc, but they do have VERID register to check the
> dw_mmc version.
> The reason why I asked is, I have seen inconsistency in card
> enumeration on few controller version, and this patch alone does not
> help, and adding a call to dw_mci_idmac_reset() after DMA reset is
> needed. And this is what is recommended in the synopsys's data book
> also.
> Do you see any issue/side effect after adding dw_mci_idmac_reset()?

A quick test shows no problem with adding this to Sonny's patch:

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 66dc8fe..588b5b8 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -481,6 +481,7 @@ static void dw_mci_idmac_start_dma(struct dw_mci
*host, unsigned int 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);

I'll start reboot tests now to see how it behaves... I think Sonny is
out of the office for a few days so we might need to wait for a spin,
but I'll run with that change in the meantime and see how it behaves
for me.


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