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

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Message-ID: <a8350d0f-2a63-46de-86f3-c156809cca0e@quicinc.com>
Date: Wed, 19 Feb 2025 17:08:52 +0530
From: Jagadeesh Kona <quic_jkona@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bryan O'Donoghue
	<bryan.odonoghue@...aro.org>
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>,
        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 2/18/2025 10:49 PM, Dmitry Baryshkov wrote:
> 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.
> 

I earlier tried moving the attach PDs call to qcom_cc_map(), but I faced the below issues
1. desc passed to qcom_cc_map() has const qualifier, so updating desc->pd_list
   inside qcom_cc_map() is leading to a warning.
2. If we attach the PDs after calling get_sync() on device, I observed
   that PDS are not getting enabled during probe. Currently qcom_cc_map()
   is called after get_sync() is already called on device.

Probably, we can add a new function qcom_cc_attach_pds_map() where we can
attach PDs and call qcom_cc_map() inside it. We can then invoke this new
function at the start of probe before get_sync(). I will post this change
in next version if this aligns with your thoughts.

Thanks,
Jagadeesh