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SubjectRe: [PATCH v4 3/3] mmc: dw_mmc: Don't start command while data busy
From
Addy,

On Fri, Feb 13, 2015 at 10:17 PM, Addy Ke <addy.ke@rock-chips.com> wrote:
> We should wait until unbusy before the next request.
> But this does't need if the command is CMD13, which can access
> SD Status register regardless of data busy.
>
> Signed-off-by: Addy Ke <addy.ke@rock-chips.com>
> ---
> Changes in v4:
> - CMD13 doesn't need wait until unbusy.
>
> 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 ac21863..692d97a 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1076,6 +1076,10 @@ static void dw_mci_request(struct mmc_host *mmc, struct mmc_request *mrq)
>
> WARN_ON(slot->mrq);
>
> + /* Wait until unbusy if the command isn't CMD13 */
> + if (mrq->cmd->opcode != MMC_SEND_STATUS)
> + dw_mci_wait_busy(slot);
> +

I think you need to be more general. You really should be checking
"cmd_flags & SDMMC_CMD_PRV_DAT_WAIT". That leverages dw_mmc's
knowledge about whether it needs to wait. Right now you'll be waiting
for CMD52 (SDIO) which I don't think is a good idea.

It also seems like this would be better in dw_mci_start_command() so
that we have the least chance of hitting the case. The downside is
that you can't sleep there, though... Hrm.

I updated a version of my take on this at
<https://chromium-review.googlesource.com/#/c/244850/>. I'll put a
timeout on it soon-ish. Any extra testing that folks can do would be
appreciated...

-Doug


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