linux-kernel - Re: [PATCH] mmc: sdhci-msm: pervent access to suspended controller

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Date: Tue, 16 Apr 2024 17:27:59 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Mantas Pucka <mantas@...vices.com>, Bjorn Andersson
 <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>,
 Georgi Djakov <djakov@...nel.org>, Pramod Gurav <pramod.gurav@...aro.org>,
 Ritesh Harjani <ritesh.list@...il.com>, linux-mmc@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org, Thierry Reding <thierry.reding@...il.com>,
 Liming Sun <limings@...dia.com>,
 Victor Shih <victor.shih@...esyslogic.com.tw>
Subject: Re: [PATCH] mmc: sdhci-msm: pervent access to suspended controller

On 5/04/24 00:13, Ulf Hansson wrote:
> On Thu, 4 Apr 2024 at 20:42, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> On 28/03/24 16:20, Adrian Hunter wrote:
>>> On 27/03/24 17:17, Ulf Hansson wrote:
>>>> On Tue, 26 Mar 2024 at 11:25, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>>>>
>>>>> On 21/03/24 16:30, Mantas Pucka wrote:
>>>>>> Generic sdhci code registers LED device and uses host->runtime_suspended
>>>>>> flag to protect access to it. The sdhci-msm driver doesn't set this flag,
>>>>>> which causes a crash when LED is accessed while controller is runtime
>>>>>> suspended. Fix this by setting the flag correctly.
>>>>>>
>>>>>> Cc: stable@...r.kernel.org
>>>>>> Fixes: 67e6db113c90 ("mmc: sdhci-msm: Add pm_runtime and system PM support")
>>>>>> Signed-off-by: Mantas Pucka <mantas@...vices.com>
>>>>>
>>>>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
>>>>
>>>> Looks like this problem may exist for other sdhci drivers too. In
>>>> particular for those that enables runtime PM, don't set
>>>> SDHCI_QUIRK_NO_LED and don't use sdhci_runtime|suspend_resume_host().
>>>>
>>>> Don't know if there is a better way to address this, if not on a case
>>>> by case basis. Do you have any thoughts about this?
>>>
>>> Yes probably case by case, but I will look at it.
>>
>> There seem to be 3 that use runtime pm but not
>> sdhci_runtime_suspend_host():
>>
>> 1. dwcmshc_runtime_suspend() : only turns off the card clock
>> via SDHCI_CLOCK_CONTROL register, so registers are presumably
>> still accessible
>>
>> 2. gl9763e_runtime_suspend() : ditto
>>
>> 3. sdhci_tegra_runtime_suspend() : disables the functional
>> clock via clk_disable_unprepare(), so registers are presumably
>> still accessible
>>
>> sdhci_msm_runtime_suspend() is different because it also turns
>> off the interface clock.
>>
>> But it looks like there are no similar cases.
> 
> Not sure we should care, but it still looks a bit fragile to me. We
> may also have a power-domain hooked up to the device, that could get
> power gated too, in which case it's likely affecting the access to
> registers.

Thought some more about this, but there isn't an easy way to know
if drivers are catering for SDIO card interrupt or SD card detect
interrupt.