linux-kernel - Re: [PATCH v2] mmc: dw_mmc: Don't start commands while busy

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Date:	Wed, 25 Feb 2015 19:22:39 +0100
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Doug Anderson <dianders@...omium.org>,
	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>, chris@...ntf.net,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mmc: dw_mmc: Don't start commands while busy

Hello Doug,

On 02/20/2015 09:31 PM, Doug Anderson 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.
> 
> Note that this also has the advantage of making sure that we don't
> change the clock while the card is busy, too.
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>
>

On an Exynos5250 Snow, Exynos5420 Peach Pit and Exynos5800 Peach Pi:

Tested-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>

Best regards,
Javier
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