linux-kernel - Re: [PATCH v3 3/7] media: iris: scale MMCX power domain on SM8250

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Message-ID: <3bmmqdn652xm5ja5mqq3epmycthjnhhgllm5guhc5jzn42mycj@kdjqjkhuvjkr>
Date: Thu, 5 Feb 2026 12:55:56 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Taniya Das <quic_tdas@...cinc.com>,
        Jonathan Marek <jonathan@...ek.ca>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Bryan O'Donoghue <bod@...nel.org>,
        Vikash Garodia <vikash.garodia@....qualcomm.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Hans Verkuil <hverkuil@...nel.org>,
        Stefan Schmidt <stefan.schmidt@...aro.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Dikshita Agarwal <dikshita@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-media@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: Re: [PATCH v3 3/7] media: iris: scale MMCX power domain on SM8250

On Thu, Feb 05, 2026 at 04:09:35PM +0530, Dikshita Agarwal wrote:
> 
> 
> On 2/4/2026 6:29 AM, Dmitry Baryshkov wrote:
> > On SM8250 most of the video clocks are powered by the MMCX domain, while
> > the PLL is powered on by the MX domain. Extend the driver to support
> > scaling both power domains, while keeping compatibility with the
> > existing DTs, which define only the MX domain.
> > 
> > Fixes: 79865252acb6 ("media: iris: enable video driver probe of SM8250 SoC")
> > Reviewed-by: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> > ---
> >  drivers/media/platform/qcom/iris/iris_platform_gen1.c | 2 +-
> >  drivers/media/platform/qcom/iris/iris_probe.c         | 7 +++++++
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/platform/qcom/iris/iris_platform_gen1.c b/drivers/media/platform/qcom/iris/iris_platform_gen1.c
> > index df8e6bf9430e..aa71f7f53ee3 100644
> > --- a/drivers/media/platform/qcom/iris/iris_platform_gen1.c
> > +++ b/drivers/media/platform/qcom/iris/iris_platform_gen1.c
> > @@ -281,7 +281,7 @@ static const struct bw_info sm8250_bw_table_dec[] = {
> >  
> >  static const char * const sm8250_pmdomain_table[] = { "venus", "vcodec0" };
> >  
> > -static const char * const sm8250_opp_pd_table[] = { "mx" };
> > +static const char * const sm8250_opp_pd_table[] = { "mx", "mmcx" };
> >  
> >  static const struct platform_clk_data sm8250_clk_table[] = {
> >  	{IRIS_AXI_CLK,  "iface"        },
> > diff --git a/drivers/media/platform/qcom/iris/iris_probe.c b/drivers/media/platform/qcom/iris/iris_probe.c
> > index 7b612ad37e4f..74ec81e3d622 100644
> > --- a/drivers/media/platform/qcom/iris/iris_probe.c
> > +++ b/drivers/media/platform/qcom/iris/iris_probe.c
> > @@ -64,6 +64,13 @@ static int iris_init_power_domains(struct iris_core *core)
> >  		return ret;
> >  
> >  	ret =  devm_pm_domain_attach_list(core->dev, &iris_opp_pd_data, &core->opp_pmdomain_tbl);
> > +	/* backwards compatibility for incomplete ABI SM8250 */
> > +	if (ret == -ENODEV &&
> > +	    of_device_is_compatible(core->dev->of_node, "qcom,sm8250-venus")) {
> 
> A query here, is it okay to have compatible based checks in driver?
> 
> I don't have the links but I remember receiving negative feedback on having
> such compatible based checks.

In general, it's better to use platform data. In this case we have a
case of keeping comatibility for exacrly one platform. Adding that to
platform data would be meaningless for all other platforms.

> 
> Thanks,
> Dikshita
> > +		iris_opp_pd_data.num_pd_names--;
> > +		ret = devm_pm_domain_attach_list(core->dev, &iris_opp_pd_data,
> > +						 &core->opp_pmdomain_tbl);
> > +	}
> >  	if (ret < 0)
> >  		return ret;
> >  
> > 

-- 
With best wishes
Dmitry