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Message-ID: <ff395fd4-1100-6276-f8c5-a3815b64ceb8@linaro.org>
Date:   Fri, 2 Jun 2023 10:48:27 +0200
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Subject: Re: [PATCH 4/4] clk: qcom: mmcc-msm8998: Fix the SMMU GDSC
To:     Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@somainline.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Imran Khan <kimran@codeaurora.org>,
        Rajendra Nayak <quic_rjendra@quicinc.com>,
        Joonwoo Park <joonwoop@codeaurora.org>,
        Jeffrey Hugo <jhugo@codeaurora.org>,
        Marijn Suijten <marijn.suijten@somainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Jami Kettunen <jami.kettunen@somainline.org>,
        linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org
References: <20230531-topic-8998_mmssclk-v1-0-2b5a8fc90991@linaro.org>
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 <CAOCk7Nogy3+5rvyzPEgsyJe7xE_17MXVs-=mniJJj=ELsCqzNQ@mail.gmail.com>
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From:   Konrad Dybcio <konrad.dybcio@linaro.org>
In-Reply-To: <CAOCk7Nogy3+5rvyzPEgsyJe7xE_17MXVs-=mniJJj=ELsCqzNQ@mail.gmail.com>
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On 1.06.2023 16:14, Jeffrey Hugo wrote:
> On Wed, May 31, 2023 at 3:01 AM Konrad Dybcio <konrad.dybcio@linaro.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@linaro.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