linux-kernel - Re: [PATCH v6 4/6] clk: qcom: gpucc-sc7280: Add cx collapse reset support

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Message-ID: <ff2d8784-0cf9-fac9-4360-71cac30fbd76@linaro.org>
Date:   Thu, 1 Sep 2022 13:46:36 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        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 v6 4/6] clk: qcom: gpucc-sc7280: Add cx collapse reset
 support

On 01/09/2022 13:34, Philipp Zabel wrote:
> On Wed, Aug 31, 2022 at 10:48:25AM +0530, Akhil P Oommen wrote:
>> Allow a consumer driver to poll for cx gdsc collapse through Reset
>> framework.
>>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>>
>> (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,
> 
> This should be accompanied by a comment explaining the not-quite-reset
> nature of this workaround, i.e. what is the prerequisite for this to
> actually work as expected?
> 
>> +};
>> +
>> +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),
> 
> See my comment on patch 2. I think instead of adding a const struct
> qcom_reset_ops * to gpucc_sc7280_resets, this should just add a const
> struct reset_control * to gpu_cc_sc7280_desc.

While this will work for the sc7280, the platform that Akhil was 
developing, this will not work for other platforms (like sm8250), where 
the dispcc also provides traditional BCR resets.

-- 
With best wishes
Dmitry