linux-kernel - Re: [PATCH 4/5] clk: qcom: videocc: Add support to attach multiple power domains

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Message-ID: <huluiiaqmunvmffoqadrhssd3kl2toutqtcw7rzamv3sqdglsf@7lz66x4sj3gv>
Date: Tue, 18 Feb 2025 19:19:40 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Cc: Jagadeesh Kona <quic_jkona@...cinc.com>, 
	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>, 
	Konrad Dybcio <konradybcio@...nel.org>, Ajit Pandey <quic_ajipan@...cinc.com>, 
	Imran Shaik <quic_imrashai@...cinc.com>, Taniya Das <quic_tdas@...cinc.com>, 
	Satya Priya Kakitapalli <quic_skakitap@...cinc.com>, linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] clk: qcom: videocc: Add support to attach multiple
 power domains

On Tue, Feb 18, 2025 at 03:46:15PM +0000, Bryan O'Donoghue wrote:
> On 18/02/2025 14:26, Jagadeesh Kona wrote:
> > During boot-up, the PLL configuration might be missed even after
> > calling pll_configure() from the clock controller probe. This can
> > happen because the PLL is connected to one or more rails that are
> > turned off, and the current clock controller code cannot enable
> > multiple rails during probe. Consequently, the PLL may be activated
> > with suboptimal settings, causing functional issues.
> > 
> > To properly configure the video PLLs in the probe on SM8450, SM8475,
> > SM8550, and SM8650 platforms, the MXC rail must be ON along with MMCX.
> > Therefore, add support to attach multiple power domains to videocc on
> > these platforms.
> > 
> > Signed-off-by: Jagadeesh Kona <quic_jkona@...cinc.com>
> > ---
> >   drivers/clk/qcom/videocc-sm8450.c | 4 ++++
> >   drivers/clk/qcom/videocc-sm8550.c | 4 ++++
> >   2 files changed, 8 insertions(+)
> > 
> > diff --git a/drivers/clk/qcom/videocc-sm8450.c b/drivers/clk/qcom/videocc-sm8450.c
> > index f26c7eccb62e7eb8dbd022e2f01fa496eb570b3f..b50a14547336580de88a741f1d33b126e9daa848 100644
> > --- a/drivers/clk/qcom/videocc-sm8450.c
> > +++ b/drivers/clk/qcom/videocc-sm8450.c
> > @@ -437,6 +437,10 @@ static int video_cc_sm8450_probe(struct platform_device *pdev)
> >   	struct regmap *regmap;
> >   	int ret;
> > +	ret = qcom_cc_attach_pds(&pdev->dev, &video_cc_sm8450_desc);
> > +	if (ret)
> > +		return ret;
> > +
> >   	ret = devm_pm_runtime_enable(&pdev->dev);
> >   	if (ret)
> >   		return ret;
> > diff --git a/drivers/clk/qcom/videocc-sm8550.c b/drivers/clk/qcom/videocc-sm8550.c
> > index 7c25a50cfa970dff55d701cb24bc3aa5924ca12d..d4b223d1392f0721afd1b582ed35d5061294079e 100644
> > --- a/drivers/clk/qcom/videocc-sm8550.c
> > +++ b/drivers/clk/qcom/videocc-sm8550.c
> > @@ -542,6 +542,10 @@ static int video_cc_sm8550_probe(struct platform_device *pdev)
> >   	int ret;
> >   	u32 sleep_clk_offset = 0x8140;
> > +	ret = qcom_cc_attach_pds(&pdev->dev, &video_cc_sm8550_desc);
> > +	if (ret)
> > +		return ret;
> > +
> >   	ret = devm_pm_runtime_enable(&pdev->dev);
> >   	if (ret)
> >   		return ret;
> > 
> 
> What's the difference between doing the attach here or doing it in
> really_probe() ?

I'd second this. If the domains are to be attached before calling any
other functions, move the call to the qcom_cc_map(), so that all drivers
get all domains attached before configuring PLLs instead of manually
calling the function.

> There doesn't seem to be any difference except that we will have an
> additional delay introduced.
> 
> Are you describing a race condition ?
> 
> I don't see _logic_ here to moving the call into the controller's higher
> level probe.
> 
> Can you describe some more ?
> 
> ---
> bod

-- 
With best wishes
Dmitry