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

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Message-ID: <eec2869a-fa8f-4aaf-9fc5-e7a8baf0f864@linaro.org>
Date: Tue, 18 Feb 2025 15:46:15 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: 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>
Cc: 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 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() ?

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