linux-kernel - Re: [PATCH 5/8] tty: mps2-uart: Use devm_clk_get

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Message-ID: <bde84e3f-5f16-473a-9674-11bef0bb2c91@vivo.com>
Date: Thu, 22 Aug 2024 21:29:01 +0800
From: Lei Liu <liulei.rjpt@...o.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Paul Cercueil <paul@...pouillou.net>,
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Subject: Re: [PATCH 5/8] tty: mps2-uart: Use devm_clk_get_enabled() helpers


on 2024/8/22 21:19, Andy Shevchenko wrote:
> On Thu, Aug 22, 2024 at 11:39:09AM +0800, Lei Liu wrote:
>> The devm_clk_get_enabled() helpers:
>>      - call devm_clk_get()
>>      - call clk_prepare_enable() and register what is needed in order to
>>       call clk_disable_unprepare() when needed, as a managed resource.
>>
>> This simplifies the code and avoids calls to clk_disable_unprepare().
> ...
>
>> -	mps_port->clk = devm_clk_get(&pdev->dev, NULL);
>> +	mps_port->clk = devm_clk_get_enabled(&pdev->dev, NULL);
>>   	if (IS_ERR(mps_port->clk))
>>   		return PTR_ERR(mps_port->clk);
>>   
>> -	ret = clk_prepare_enable(mps_port->clk);
>> -	if (ret)
>> -		return ret;
>> -
>>   	mps_port->port.uartclk = clk_get_rate(mps_port->clk);
>>   
>> -	clk_disable_unprepare(mps_port->clk);
> Your change is not equivalent. In case this clock is shared this may lead to
> run-time issues. Hence I don't think this patch is needed in this case.
> Instead, you may add a comment on top of devm_clk_get() to explain that we only
> need it be enabled to get clock rate in the probe.

Thank you for your suggestion. I will adopt your advice in the second 
version of the patch and make no changes.

---
With Best Regards,

Lei Liu