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

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Message-ID: <20250610120351.GQ8020@e132581.arm.com>
Date: Tue, 10 Jun 2025 13:03:51 +0100
From: Leo Yan <leo.yan@....com>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	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 Tue, Jun 10, 2025 at 04:09:32PM +0530, Anshuman Khandual wrote:
> 
> 
> 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;

If it is an AMBA device, we should return a NULL pointer, as this
indicates that the APB clock is not managed by the CoreSight driver.

In this patch, I did not perform any refactoring and simply made a
straightforward changed.  The refactoring is done in the patch 07, as
you suggested, where the function is refined as:

    if (dev_is_amba(dev)) {
        return NULL;
    } else {
        pclk = devm_clk_get_enabled(dev, "apb_pclk");
        ...
    }

Would it be acceptable to keep this patch as it is?

Thanks,
Leo