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

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Message-ID: <6016f2ec-6918-471c-a8dc-0aa98fc2b824@quicinc.com>
Date: Wed, 21 Aug 2024 13:54:57 +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 2/2] clk: qcom: Add support for Global Clock Controller on
 QCS8300



On 8/20/2024 7:36 PM, 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 */
>> +	qcom_branch_set_clk_en(regmap, 0x32004); /* GCC_CAMERA_AHB_CLK */
>> +	qcom_branch_set_clk_en(regmap, 0x32020); /* GCC_CAMERA_XO_CLK */
> 
> It would be good to document why. Why does the camera driver not
> enable the clock when it loads?
> 
>> +	qcom_branch_set_clk_en(regmap, 0x33004); /* GCC_DISP_AHB_CLK */
>> +	qcom_branch_set_clk_en(regmap, 0x33018); /* GCC_DISP_XO_CLK */
>> +	qcom_branch_set_clk_en(regmap, 0x7d004); /* GCC_GPU_CFG_AHB_CLK */
>> +	qcom_branch_set_clk_en(regmap, 0x34004); /* GCC_VIDEO_AHB_CLK */
>> +	qcom_branch_set_clk_en(regmap, 0x34024); /* GCC_VIDEO_XO_CLK */
> 
> Why cannot the display driver enable the clock when it loads?
> 

These clocks require for DISPCC and CAMCC drivers for register access, 
hence kept enabled at GCC driver probe. The same approach is followed 
for all the targets.

Thanks,
Imran
> 	Andrew