linux-kernel - Re: [PATCH] regulator: qcom-rpmh: Use PROBE_FORCE

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Date:   Fri, 24 Mar 2023 12:18:53 +0100
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regulator: qcom-rpmh: Use PROBE_FORCE_SYNCHRONOUS

Hi,

On 23.03.2023 23:08, Doug Anderson wrote:
> On Thu, Mar 23, 2023 at 3:05 PM Marek Szyprowski
> <m.szyprowski@...sung.com> wrote:
>> Restore synchronous probing for 'qcom,pm8150-rpmh-regulators' because
>> otherwise the UFSHC device is not properly initialized on QRB5165-RB5
>> board.
>>
>> Fixes: ed6962cc3e05 ("regulator: Set PROBE_PREFER_ASYNCHRONOUS for drivers between 4.14 and 4.19")
>> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
>> ---
>>   drivers/regulator/qcom-rpmh-regulator.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
> I don't object to this patch landing temporarily, but can you provide
> any more details, please? On Qualcomm Chromebooks I'm not seeing any
> issues with RPMH regulators probing asynchronously, so I can only
> assume that there's a bug in the UFSHC driver that's being tickled.

You are right. I've analyzed this case further and it turned out that it 
was my fault. In short - 'rootwait' kernel cmdline parameter was missing 
and root was specified as '/dev/sda7'.

UFSHC driver properly retried probing after it cannot get its 
regulators, but it happened at the same time when kernel tried to mount 
rootfs. I was confused that this is really a regulator issue, because 
the mentioned /dev/sda* devices were properly reported as available in 
the system in the root mounting failure message, but adding the 
'rootwait' cmdline parameter fixed this problem. It would be safe to 
revert this change. I'm really sorry for the false report and the noise.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland