linux-kernel - Re: [PATCH v2 2/2] clk: qcom: Add support for Global Clock Controller on QCS8300

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Message-ID: <01c5178e-58fe-4c45-a82e-d0b6b6789645@quicinc.com>
Date: Mon, 26 Aug 2024 16:25:39 +0530
From: Imran Shaik <quic_imrashai@...cinc.com>
To: Andrew Lunn <andrew@...n.ch>
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>,
        Richard Cochran <richardcochran@...il.com>,
        "Ajit
 Pandey" <quic_ajipan@...cinc.com>,
        Taniya Das <quic_tdas@...cinc.com>,
        Jagadeesh Kona <quic_jkona@...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>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] clk: qcom: Add support for Global Clock Controller
 on QCS8300



On 8/23/2024 1:29 AM, Andrew Lunn wrote:
>> +static int gcc_qcs8300_probe(struct platform_device *pdev)
>> +{
>> +	struct regmap *regmap;
>> +	int ret;
>> +
>> +	regmap = qcom_cc_map(pdev, &gcc_qcs8300_desc);
>> +	if (IS_ERR(regmap))
>> +		return PTR_ERR(regmap);
>> +
>> +	ret = qcom_cc_register_rcg_dfs(regmap, gcc_dfs_clocks,
>> +				       ARRAY_SIZE(gcc_dfs_clocks));
>> +	if (ret)
>> +		return ret;
>> +
>> +	/* Keep some clocks always enabled */
> 
> Sorry, but you need to explain why. Why cannot the camera driver
> enable these clocks when it loads? Why cannot the display driver
> enable these clocks when it loads.
> 

These clocks are recommended to be kept always ON as per the HW design 
and also exposing clock structures and marking them critical in the 
kernel would lead to redundant code. Based on previous discussions with 
clock maintainers, it is recommended to keep such clocks enabled at 
probe and not model them. This approach is consistently followed for all 
other targets as well.

Thanks,
Imran

> 	Andrew