linux-kernel - Re: [PATCH v6 2/4] media: venus: pm_helpers: use opp-table for the frequency

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Message-ID: <ac145c57-1db3-4747-88e2-02825f958d5a@oss.qualcomm.com>
Date: Thu, 9 Jan 2025 14:05:41 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Renjiang Han <quic_renjiang@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/4] media: venus: pm_helpers: use opp-table for the
 frequency

On 2.01.2025 6:38 AM, Renjiang Han wrote:
> 
> On 12/23/2024 10:17 PM, Konrad Dybcio wrote:
>> On 19.12.2024 6:41 AM, Renjiang Han wrote:
>>> The frequency value in the opp-table in the device tree and the freq_tbl
>>> in the driver are the same.
>>>
>>> Therefore, update pm_helpers.c to use the opp-table for frequency values
>>> for the v4 core.
>>> If getting data from the opp table fails, fall back to using the frequency
>>> table.
>>>
>>> Signed-off-by: Renjiang Han<quic_renjiang@...cinc.com>
>>> ---
>>>   drivers/media/platform/qcom/venus/pm_helpers.c | 53 +++++++++++++++++++-------
>>>   1 file changed, 39 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/qcom/venus/pm_helpers.c b/drivers/media/platform/qcom/venus/pm_helpers.c
>>> index 33a5a659c0ada0ca97eebb5522c5f349f95c49c7..b61c0ad152878870b7223efa274e137d3636433b 100644
>>> --- a/drivers/media/platform/qcom/venus/pm_helpers.c
>>> +++ b/drivers/media/platform/qcom/venus/pm_helpers.c
>>> @@ -43,14 +43,20 @@ static int core_clks_enable(struct venus_core *core)
>>>       const struct venus_resources *res = core->res;
>>>       const struct freq_tbl *freq_tbl = core->res->freq_tbl;
>>>       unsigned int freq_tbl_size = core->res->freq_tbl_size;
>>> +    struct device *dev = core->dev;
>>> +    struct dev_pm_opp *opp;
>>>       unsigned long freq;
>>>       unsigned int i;
>>>       int ret;
>>>   -    if (!freq_tbl)
>>> -        return -EINVAL;
>>> -
>>> -    freq = freq_tbl[freq_tbl_size - 1].freq;
>>> +    opp = dev_pm_opp_find_freq_ceil(dev, &freq);
>>> +    if (IS_ERR(opp)) {
>>> +        if (!freq_tbl)
>>> +            return -EINVAL;
>>> +        freq = freq_tbl[freq_tbl_size - 1].freq;
>>> +    } else {
>>> +        dev_pm_opp_put(opp);
>>> +    }
>> I'm not super convinced how this could have ever worked without
>> scaling voltage levels, by the way. Perhaps this will squash some
>> random bugs :|
>>
>> Konrad
>  Thanks for your comment.
>  The default value of freq is 0, and then dev_pm_opp_find_freq_ceil is
>  used to match freq to the maximum value in opp-table that is close to
>  0. The frequency values in opp-table and freq_tbl are the same, and
>  dev_pm_opp_find_freq_ceil is used to assign the minimum value in
>  opp-table to freq. So the logic is the same as before. I'm not sure if
>  I've answered your concern.

We talked offline, but for the record: my concern here was about
clk_set_rate() not scaling RPM/h voltage corners, which this patch
fixes

Konrad