linux-kernel - Re: [PATCH] mmc: dw_mmc: Don't start commands while busy

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Date:	Fri, 20 Feb 2015 12:31:14 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Addy Ke <addy.ke@...k-chips.com>,
	Alexandru Stan <amstan@...omium.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Doug Anderson <dianders@...omium.org>,
	Chris Ball <chris@...ntf.net>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: dw_mmc: Don't start commands while busy

Hi,

On Fri, Feb 20, 2015 at 10:49 AM, Doug Anderson <dianders@...omium.org> wrote:
> We've seen problems on some WiFi modules where we seem to send a CMD53
> (which requires the data lines) while the module is asserting busy.
> We shouldn't do that.
>
> The Designware Databook says that before issuing a new data transfer
> command we should check for busy, so that's what we'll do.
>
> We'll leverage the existing dw_mmc knowledge about whether it should
> wait for the previous command to finish to know whether we should
> check for busy before sending the command.  This means we won't end up
> incorrectly waiting for things like CMD52 (SDIO) or CMD13 (SD) which
> don't use the data line.
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  drivers/mmc/host/dw_mmc.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)

Sorry for the quick spin.  After I posted this I re-read all the
messages and it looks like Addy has an actual SD card (not SDIO) that
is also asserting busy.  He's seeing it assert busy around the clock
update.

I believe his bug can be fixed by also adding the busy check to
mci_send_cmd(), so I'll shortly post V2 of this patch.  Hopefully Addy
will be able to test all 3 of my patches together and his card will be
totally happy.

-Doug
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