linux-kernel - Re: [PATCH v2 5/7] arm64: dts: qcom: sc7280: Update gpu register list

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Date:   Thu, 14 Jul 2022 11:10:29 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Taniya Das <quic_tdas@...cinc.com>, <quic_rjendra@...cinc.com>
CC:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Matthias Kaehlcke <mka@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        "Stephen Boyd" <swboyd@...omium.org>
Subject: Re: [PATCH v2 5/7] arm64: dts: qcom: sc7280: Update gpu register list

On 7/12/2022 4:57 AM, Doug Anderson wrote:
> Hi,
>
> On Fri, Jul 8, 2022 at 11:00 PM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>> Update gpu register array with gpucc memory region.
>>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> ---
>>
>> (no changes since v1)
>>
>>   arch/arm64/boot/dts/qcom/sc7280.dtsi | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/qcom/sc7280.dtsi b/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> index e66fc67..defdb25 100644
>> --- a/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/sc7280.dtsi
>> @@ -2228,10 +2228,12 @@
>>                          compatible = "qcom,adreno-635.0", "qcom,adreno";
>>                          reg = <0 0x03d00000 0 0x40000>,
>>                                <0 0x03d9e000 0 0x1000>,
>> -                             <0 0x03d61000 0 0x800>;
>> +                             <0 0x03d61000 0 0x800>,
>> +                             <0 0x03d90000 0 0x2000>;
>>                          reg-names = "kgsl_3d0_reg_memory",
>>                                      "cx_mem",
>> -                                   "cx_dbgc";
>> +                                   "cx_dbgc",
>> +                                   "gpucc";
> This doesn't seem right. Shouldn't you be coordinating with the
> existing gpucc instead of reaching into its registers?
>
> -Doug
IIUC, qcom gdsc driver doesn't ensure hardware is collapsed since they 
are vote-able switches. Ideally, we should ensure that the hw has 
collapsed for gpu recovery because there could be transient votes from 
other subsystems like hypervisor using their vote register.

I am not sure how complex the plumbing to gpucc driver would be to allow 
gpu driver to check hw status. OTOH, with this patch, gpu driver does a 
read operation on a gpucc register which is in always-on domain. That 
means we don't need to vote any resource to access this register.

Stephen/Rajendra/Taniya, any suggestion?

-Akhil.