linux-kernel - Re: [PATCH v2 13/15] phy: qcom-qmp-pcie: add support for pipediv2 clock

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Date:   Thu, 20 Oct 2022 13:53:03 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 13/15] phy: qcom-qmp-pcie: add support for pipediv2
 clock

On 20/10/2022 13:49, Johan Hovold wrote:
> On Thu, Oct 20, 2022 at 12:28:14PM +0300, Dmitry Baryshkov wrote:
>> On 20/10/2022 12:05, Johan Hovold wrote:
> 
>>> Here's your example diff inline:
> 
>>> @@ -2206,12 +2207,17 @@ static int qmp_pcie_parse_dt_legacy(struct qmp_pcie *qmp, struct device_node *np
>>>    		}
>>>    	}
>>>    
>>> -	qmp->pipe_clk = devm_get_clk_from_child(dev, np, NULL);
>>> -	if (IS_ERR(qmp->pipe_clk)) {
>>> -		return dev_err_probe(dev, PTR_ERR(qmp->pipe_clk),
>>> +	clk = devm_get_clk_from_child(dev, np, NULL);
>>> +	if (IS_ERR(clk)) {
>>> +		return dev_err_probe(dev, PTR_ERR(clk),
>>>    				     "failed to get pipe clock\n");
>>>    	}
>>>    
>>> +	qmp->num_pipe_clks = 1;
>>> +	qmp->pipe_clks = devm_kcalloc(dev, qmp->num_pipe_clks,
>>> +				      sizeof(*qmp->pipe_clks), GFP_KERNEL);
>>> +	qmp->pipe_clks[0].clk = clk;
>>>
>>> So here you're poking at bulk API internals and forgot to set the id
>>> string, which the implementation uses.
>>
>> I didn't forget, I just skipped setting it. Hmm. I thought that it is
>> used only for clk_bulk_get. But after checking, it seems it's also used
>> for error messages. Mea culpa.
>>
>> But it's not that I was poking into the internals. These items are in
>> the public header.
> 
> My point is that you're not using the bulk API as it was intended (e.g.
> with clk_bulk_get()) and you risk running into issues like the above.
> 
> And looking up the actual clock name for this is overkill, even in the
> case were it is provided, so we'd need to set it unconditionally to
> "pipe" (which is fine).
> 
>>> For reasons like this, and the fact that will likely never have a third
>>> pipe clock, I'm reluctant to using the bulk API.
>>
>> Let's resort to the maintainer opinion then.
> 
> I'll take another look at it too.

Thanks!

-- 
With best wishes
Dmitry