linux-kernel - Re: [PATCH v7 4/6] clk: qcom: gpucc-sc7280: Add cx collapse reset support

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Date:   Thu, 8 Dec 2022 20:54:39 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     freedreno <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Douglas Anderson <dianders@...omium.org>,
        <krzysztof.kozlowski@...aro.org>, Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, <linux-clk@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 4/6] clk: qcom: gpucc-sc7280: Add cx collapse reset
 support

On 12/7/2022 9:16 PM, Ulf Hansson wrote:
> On Wed, 5 Oct 2022 at 11:08, Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>> Allow a consumer driver to poll for cx gdsc collapse through Reset
>> framework.
> Would you mind extending this commit message, to allow us to better
> understand what part is really the consumer part.
Sure. I can do that.
>
> I was expecting the consumer part to be the GPU (adreno) driver, but I
> may have failed to understand correctly. It would be nice to see an
> example of a typical sequence, where the reset is being
> asserted/deasserted, from the consumer point of view. Would you mind
> explaining this a bit more?
https://elixir.bootlin.com/linux/v6.1-rc8/source/drivers/gpu/drm/msm/adreno/a6xx_gpu.c#L1309
You are correct. The consumer is adreno gpu driver. When there is a gpu fault, these sequences are followed:
1. drop pm_runtime_put() for gpu device which will drops its vote on 'cx' genpd. line: 1306
2. At this point, there could be vote from either smmu driver (smmu is under same power domain too) or from other subsystems (tz/hyp).
3. So we call into gdsc driver through reset interface to poll the gdsc register to ensure it collapsed at least once. Line: 1309
4. Then we turn ON gpu. line:1314.

-Akhil.
>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Kind regards
> Uffe
>
>> ---
>>
>> (no changes since v3)
>>
>> Changes in v3:
>> - Convert 'struct qcom_reset_ops cx_gdsc_reset' to 'static const' (Krzysztof)
>>
>> Changes in v2:
>> - Minor update to use the updated custom reset ops implementation
>>
>>  drivers/clk/qcom/gpucc-sc7280.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/clk/qcom/gpucc-sc7280.c b/drivers/clk/qcom/gpucc-sc7280.c
>> index 9a832f2..fece3f4 100644
>> --- a/drivers/clk/qcom/gpucc-sc7280.c
>> +++ b/drivers/clk/qcom/gpucc-sc7280.c
>> @@ -433,12 +433,22 @@ static const struct regmap_config gpu_cc_sc7280_regmap_config = {
>>         .fast_io = true,
>>  };
>>
>> +static const struct qcom_reset_ops cx_gdsc_reset = {
>> +       .reset = gdsc_wait_for_collapse,
>> +};
>> +
>> +static const struct qcom_reset_map gpucc_sc7280_resets[] = {
>> +       [GPU_CX_COLLAPSE] = { .ops = &cx_gdsc_reset, .priv = &cx_gdsc },
>> +};
>> +
>>  static const struct qcom_cc_desc gpu_cc_sc7280_desc = {
>>         .config = &gpu_cc_sc7280_regmap_config,
>>         .clks = gpu_cc_sc7280_clocks,
>>         .num_clks = ARRAY_SIZE(gpu_cc_sc7280_clocks),
>>         .gdscs = gpu_cc_sc7180_gdscs,
>>         .num_gdscs = ARRAY_SIZE(gpu_cc_sc7180_gdscs),
>> +       .resets = gpucc_sc7280_resets,
>> +       .num_resets = ARRAY_SIZE(gpucc_sc7280_resets),
>>  };
>>
>>  static const struct of_device_id gpu_cc_sc7280_match_table[] = {
>> --
>> 2.7.4
>>