linux-kernel - Re: [PATCH v3 6/9] coresight: Avoid enable programming clock duplicately

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Message-ID: <b20a6309-ae31-496d-a1ad-61ea358ad7a9@arm.com>
Date: Tue, 10 Jun 2025 16:09:32 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Leo Yan <leo.yan@....com>, Suzuki K Poulose <suzuki.poulose@....com>
Cc: Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, coresight@...ts.linaro.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/9] coresight: Avoid enable programming clock
 duplicately



On 09/06/25 10:44 PM, Leo Yan wrote:
> On Mon, Jun 09, 2025 at 05:58:34PM +0100, Suzuki Kuruppassery Poulose wrote:
> 
> [...]
> 
>>>   static inline struct clk *coresight_get_enable_apb_pclk(struct device *dev)
>>>   {
>>> -	struct clk *pclk;
>>> +	struct clk *pclk = NULL;
>>> -	pclk = devm_clk_get_enabled(dev, "apb_pclk");
>>> -	if (IS_ERR(pclk))
>>> -		pclk = devm_clk_get_enabled(dev, "apb");
>>> +	if (!dev_is_amba(dev)) {
>>> +		pclk = devm_clk_get_enabled(dev, "apb_pclk");
>>> +		if (IS_ERR(pclk))
>>> +			pclk = devm_clk_get_enabled(dev, "apb");
>>
>> AMBA driver doesn't handle "apb" clock ? So we may need to retain that here
>> ?
> 
> Here checks the condition "if (!dev_is_amba(dev))", it means the device
> is not an AMBA device (e.g., a platform device), the APB clock is
> enabled at here.

Just exit early for AMBA devices when 'pclk' clock is still NULL ?

	if (dev_is_amba(dev))
		return pclk;

> 
> Otherwise, for a AMBA device, the AMBA bus layer will help to enable
> APB clock.
> 
>> Otherwise looks good to me.
>>
>> Suzuki
>>> +	}
>>>   	return pclk;
>>>   }
>>>
>>