linux-kernel - Re: [PATCH 1/2] mmc: dw_mmc: Only enable CD after setup and only if needed

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Message-ID: <54EE19E9.9090501@collabora.co.uk>
Date:	Wed, 25 Feb 2015 19:52:25 +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>,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, chris@...ntf.net,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mmc: dw_mmc: Only enable CD after setup and only
 if needed

Hello Doug,

On 02/25/2015 07:11 PM, Doug Anderson wrote:
> We really don't want to get a card detect interrupt during probe time
> since it can confuse things.  Let's disable the card detect interrupt
> until we're in a really good place: the end of probe.  Let's also
> simply avoid enabling the card detect interrupt if it's not used.
> 
> It appears that (at least on rk3288) when vqmmc is turned on it can
> cause a bogus "card detect" interrupt.  That meant that we were
> getting a predictable card detect interrupt while we were in
> mmc_add_host().  On the version of the kernel I'm working with at
> least (3.14), this is not a great time to get a card detect interrupt
> since I think that we don't grab all the needed locks in
> mmc_add_host() and children.  I put stack dumps in dw_mci_setup_bus()
> and found that I could see two distinct stack crawls that looked like:
> 
> Caller one:
> * dw_mci_setup_bus
> * dw_mci_set_ios
> * mmc_power_up
> * mmc_start_host
> * mmc_add_host
> 
> Caller two:
> * dw_mci_setup_bus
> * dw_mci_set_ios
> * mmc_set_chip_select
> * mmc_go_idle
> * mmc_rescan
> * process_one_work
> * worker_thread
> * kthread
> 
> 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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