linux-kernel - Re: [PATCH v2 1/2] phy: qcom: pcie: Determine has_nocsr

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Message-ID: <5bbd6b38-5c8d-65b2-f910-b125519bd037@quicinc.com>
Date: Thu, 13 Feb 2025 16:09:53 +0800
From: "Wenbin Yao (Consultant)" <quic_wenbyao@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Philipp Zabel
	<p.zabel@...gutronix.de>, <vkoul@...nel.org>,
        <kishon@...nel.org>, <dmitry.baryshkov@...aro.org>,
        <abel.vesa@...aro.org>, <quic_qianyu@...cinc.com>,
        <neil.armstrong@...aro.org>, <manivannan.sadhasivam@...aro.org>,
        <quic_devipriy@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <linux-phy@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] phy: qcom: pcie: Determine has_nocsr_reset
 dynamically

On 2/12/2025 8:31 PM, Konrad Dybcio wrote:
> On 11.02.2025 10:53 AM, Philipp Zabel wrote:
>> On Di, 2025-02-11 at 17:42 +0800, Wenbin Yao wrote:
>>> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>>
>>> Decide the in-driver logic based on whether the nocsr reset is present
>>> and defer checking the appropriateness of that to dt-bindings to save
>>> on boilerplate.
>>>
>>> Reset controller APIs are fine consuming a nullptr, so no additional
>>> checks are necessary there.
>>>
>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>> Signed-off-by: Wenbin Yao <quic_wenbyao@...cinc.com>
>>> Reviewed-by: Abel Vesa <abel.vesa@...aro.org>
>>> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>> ---
> [...]
>
>>>   static void qmp_pcie_init_port_b(struct qmp_pcie *qmp, const struct qmp_phy_cfg_tbls *tbls)
>>> @@ -4203,11 +4196,14 @@ static int qmp_pcie_reset_init(struct qmp_pcie *qmp)
>>>   	if (ret)
>>>   		return dev_err_probe(dev, ret, "failed to get resets\n");
>>>   
>>> -	if (cfg->has_nocsr_reset) {
>>> -		qmp->nocsr_reset = devm_reset_control_get_exclusive(dev, "phy_nocsr");
>>> -		if (IS_ERR(qmp->nocsr_reset))
>>> +	qmp->nocsr_reset = devm_reset_control_get_exclusive(dev, "phy_nocsr");
>>> +	if (IS_ERR(qmp->nocsr_reset)) {
>>> +		if (PTR_ERR(qmp->nocsr_reset) == -ENOENT ||
>>> +		    PTR_ERR(qmp->nocsr_reset) == -EINVAL)
>> Why is -EINVAL ignored here?
> If the NOCSR (partial) reset is missing, we can still assert the "full" reset
> and program the hardware from the ground up. It's also needed for backwards
> dt compat as not all platforms described it when originally added.

Seems like we really can't ignore -EINVAL. If no_csr reset is missing in
dts, it will return -ENOENT, which is turned into NULL by
devm_reset_control_get_optional_exclusive. -EINVAL indicates something
wrong in args we passed to the function and the reset property that need to
be fixed.

>
>> Without this you could just use
>> devm_reset_control_get_optional_exclusive(), which already turns -
>> ENOENT into NULL. That seems to me the correct thing to do, as from
>> driver point-of-view, this reset control is optional.
> Good point, I forgot _optional_ was a thing in the reset framework
>
> Konrad

Will use devm_reset_control_get_optional_exclusive function in patch v3.

-- 
With best wishes
Wenbin