linux-kernel - Re: [PATCH 3/6] clk: qcom: ipq-cmn-pll: Add IPQ5018 SoC support

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Message-ID: <bd1ce180-1282-45f1-a893-5cc097eb6613@oss.qualcomm.com>
Date: Fri, 2 May 2025 12:38:10 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: george.moussalem@...look.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>, Luo Jie <quic_luoj@...cinc.com>,
        Lee Jones <lee@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] clk: qcom: ipq-cmn-pll: Add IPQ5018 SoC support

On 5/2/25 12:15 PM, George Moussalem via B4 Relay wrote:
> From: George Moussalem <george.moussalem@...look.com>
> 
> The CMN PLL in IPQ5018 SoC supplies fixed clocks to XO, sleep, and the
> ethernet block. The CMN PLL to the ethernet block must be enabled first
> by setting a specific register in the TCSR area set in the device tree.
> 
> Signed-off-by: George Moussalem <george.moussalem@...look.com>
> ---

[...]

> +static inline int ipq_cmn_pll_eth_enable(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	unsigned int cmn_pll_offset;
> +	struct regmap *tcsr;
> +	int ret;
> +
> +	tcsr = syscon_regmap_lookup_by_phandle_args(dev->of_node, "qcom,cmn-pll-eth-enable",
> +						    1, &cmn_pll_offset);

So we have syscon_regmap_lookup_by_phandle_args() and
syscon_regmap_lookup_by_phandle_optional(), but we could also
use a syscon_regmap_lookup_by_phandle_args_optional() - could
you add that in drivers/mfd/syscon.c?

> +	if (IS_ERR(tcsr)) {
> +		ret = PTR_ERR(tcsr);
> +		/*
> +		 * continue if -ENODEV is returned as not all IPQ SoCs
> +		 * need to enable CMN PLL. If it's another error, return it.
> +		 */
> +		if (ret == -ENODEV)
> +			tcsr = NULL;
> +		else
> +			return ret;
> +	}
> +
> +	if (tcsr) {
> +		ret = regmap_update_bits(tcsr, cmn_pll_offset + TCSR_CMN_PLL_ETH,

I think it's better to just pass the exact register that we need,
instead of some loosely defined subregion - especially given the
structure likely will change across platforms

> +					 TCSR_CMN_PLL_ETH_ENABLE, TCSR_CMN_PLL_ETH_ENABLE);

regmap_set_bits()

> +		if (ret)
> +			return ret;

You can initialize ret to 0 and return ret below, unconditionally

> +	}
> +
> +	return 0;
> +}
> +
>  static int ipq_cmn_pll_clk_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	int ret;
>  
> +	ret = ipq_cmn_pll_eth_enable(pdev);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "Fail to enable CMN PLL to ethernet");

Fail*ed*

Konrad