linux-kernel - Re: [PATCH 4/4] clk: qcom: mmcc-msm8998: Fix the SMMU GDSC

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Message-ID: <ff395fd4-1100-6276-f8c5-a3815b64ceb8@linaro.org>
Date:   Fri, 2 Jun 2023 10:48:27 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Jeffrey Hugo <jeffrey.l.hugo@...il.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Imran Khan <kimran@...eaurora.org>,
        Rajendra Nayak <quic_rjendra@...cinc.com>,
        Joonwoo Park <joonwoop@...eaurora.org>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 4/4] clk: qcom: mmcc-msm8998: Fix the SMMU GDSC



On 1.06.2023 16:14, Jeffrey Hugo wrote:
> On Wed, May 31, 2023 at 3:01 AM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>>
>> The SMMU GDSC doesn't have to be ALWAYS-ON and shouldn't feature the
>> HW_CTRL flag (it's separate from hw_ctrl_addr).  In addition to that,
>> it should feature a cxc entry for bimc_smmu_axi_clk and be marked as
>> votable.
>>
>> Fix all of these issues.
>>
>> Fixes: d14b15b5931c ("clk: qcom: Add MSM8998 Multimedia Clock Controller (MMCC) driver")
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> 
> Was this tested on a system where the bootloader has enabled the
> display and it is active during Linux boot?
No, I only have a device whose bootloader doesn't initialize display.

> 
> I seem to recall that in that scenario, Linux would boot up, see that
> the GDSC is on, not see any clients for it (still initializing), turn
> it off, and kill the display which then results in either a mess of
> errors or a bus lockup.
I see 2 possible scenarios: either the display shuts off (because
somebody hasn't described the hardware properly and Linux isn't)
aware of all dependencies, or we get bus errors because we only
shut down / initialize some hardware partially, also possibly due
to bad dependency description.

Konrad
> 
> -Jeff