linux-kernel - Re: [PATCH v2 3/3] media: camss: Link CAMSS power domain

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Date:   Fri, 26 May 2023 22:57:17 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Yassine Oudjana <yassine.oudjana@...il.com>,
        Robert Foss <rfoss@...nel.org>,
        Todor Tomov <todor.too@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Hans Verkuil <hansverk@...co.com>
Cc:     Yassine Oudjana <y.oudjana@...tonmail.com>,
        Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] media: camss: Link CAMSS power domain



On 26.05.2023 22:49, Bryan O'Donoghue wrote:
> On 26/05/2023 19:07, Yassine Oudjana wrote:
>> From: Yassine Oudjana <y.oudjana@...tonmail.com>
>>
>> The CAMSS power domain was previously enabled implicitly when the VFE
>> power domains were enabled.
>> Commit 46cc03175498 ("media: camss: Split power domain management")
>> delayed enabling VFE power domains which in turn delayed enabling the
>> CAMSS power domain. This made CSIPHY fail to enable camss_top_ahb_clk
>> which requires the CAMSS power domain to be on:
>>
>> [  199.097810] ------------[ cut here ]------------
>> [  199.097893] camss_top_ahb_clk status stuck at 'off'
>> [  199.097913] WARNING: CPU: 3 PID: 728 at drivers/clk/qcom/clk-branch.c:91 clk_branch_wait+0x140/0x160
>> ...
>> [  199.100064]  clk_branch_wait+0x140/0x160
>> [  199.100112]  clk_branch2_enable+0x30/0x40
>> [  199.100159]  clk_core_enable+0x6c/0xb0
>> [  199.100211]  clk_enable+0x2c/0x50
>> [  199.100257]  camss_enable_clocks+0x94/0xe0 [qcom_camss]
>> [  199.100342]  csiphy_set_power+0x154/0x2a0 [qcom_camss]
>> ...
>> [  199.101594] ---[ end trace 0000000000000000 ]---
>>
>> Link the CAMSS power domain in camss_configure_pd to make sure it gets
>> enabled before CSIPHY tries to enable clocks.
>>
>> Fixes: 02afa816dbbf ("media: camss: Add basic runtime PM support")
>> Signed-off-by: Yassine Oudjana <y.oudjana@...tonmail.com>
>> ---
>>   drivers/media/platform/qcom/camss/camss.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
>> index 1ef26aea3eae..9aea8220d923 100644
>> --- a/drivers/media/platform/qcom/camss/camss.c
>> +++ b/drivers/media/platform/qcom/camss/camss.c
>> @@ -1453,6 +1453,7 @@ static const struct media_device_ops camss_media_ops = {
>>   static int camss_configure_pd(struct camss *camss)
>>   {
>>       struct device *dev = camss->dev;
>> +    int camss_pd_index;
>>       int i;
>>       int ret;
>>   @@ -1496,7 +1497,13 @@ static int camss_configure_pd(struct camss *camss)
>>           }
>>       }
>>   -    if (i > camss->vfe_num) {
>> +    /* Link CAMSS power domain if available */
>> +    camss_pd_index = device_property_match_string(camss->dev, "power-domain-names", "camss");
>> +    if (camss_pd_index >= 0)
>> +        device_link_add(camss->dev, camss->genpd[camss_pd_index], DL_FLAG_STATELESS |
>> +                DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE);
>> +
>> +    if (i > camss->vfe_num && i != camss_pd_index) {
>>           camss->genpd_link[i - 1] = device_link_add(camss->dev, camss->genpd[i - 1],
>>                                  DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME |
>>                                  DL_FLAG_RPM_ACTIVE);
> 
> Konrad pointed this out.
> 
> Are you 100% sure you want to do this. We already have a way to count the # of power-domains in camss_configure_pd().
> 
> Your series is now adding a dependency on power-domain-names.
> 
> Is there a good reason to add that dependency ? If not, then lets just take the code from camss_configure_pd() and make it so that it can be used/reused here.
This code contains a whole bunch of hacky counting logic that should have
been substituted with _byname, but now we're stuck with indices to keep
compatibility with old DTs :/

If CAMSS_GDSC (talking about pre-TITAN hw) was a parent of all the other
CAMSS-related GDSCs, we could make it their parent in the clock driver
and call it a day.

Konrad

> 
> ---
> bod