linux-kernel - Re: [PATCH 2/3] mmc: sdhci-esdhc-imx: obtain the 'per' clock rate after its enablement

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Message-ID: <7d851eb6-ef8e-480a-9b5a-8cb67d6adf8b@oss.nxp.com>
Date: Wed, 10 Jul 2024 15:50:09 +0300
From: Ciprian Marian Costea <ciprianmarian.costea@....nxp.com>
To: Adrian Hunter <adrian.hunter@...el.com>, Haibo Chen <haibo.chen@....com>,
 Ulf Hansson <ulf.hansson@...aro.org>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, s32@....com
Subject: Re: [PATCH 2/3] mmc: sdhci-esdhc-imx: obtain the 'per' clock rate
 after its enablement

On 7/10/2024 3:33 PM, Adrian Hunter wrote:
> On 8/07/24 15:10, Ciprian Costea wrote:
>> The I.MX SDHCI driver assumes that the frequency of the 'per' clock
>> can be obtained even on disabled clocks, which is not always the case.
>>
>> According to 'clk_get_rate' documentation, it is only valid
>> once the clock source has been enabled.
> 
> The kerneldoc comment for clk_get_rate() says
> 
> 	Can be called regardless of the clock enabledness
> 
> which sounds like the opposite.  Please clarify.
>

Hello Adrian,

My observation was based on the following [1] 'clk_get_rate()' 
documentation.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/clk.h#n720

Best Regards,
Ciprian

>>
>> Signed-off-by: Ciprian Costea <ciprianmarian.costea@....nxp.com>
>> ---
>>   drivers/mmc/host/sdhci-esdhc-imx.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
>> index 21d984a77be8..8f0bc6dca2b0 100644
>> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
>> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
>> @@ -1709,7 +1709,6 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>>   	}
>>   
>>   	pltfm_host->clk = imx_data->clk_per;
>> -	pltfm_host->clock = clk_get_rate(pltfm_host->clk);
>>   	err = clk_prepare_enable(imx_data->clk_per);
>>   	if (err)
>>   		goto free_sdhci;
>> @@ -1720,6 +1719,13 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>>   	if (err)
>>   		goto disable_ipg_clk;
>>   
>> +	pltfm_host->clock = clk_get_rate(pltfm_host->clk);
>> +	if (!pltfm_host->clock) {
>> +		dev_err(mmc_dev(host->mmc), "could not get clk rate\n");
>> +		err = -EINVAL;
>> +		goto disable_ahb_clk;
>> +	}
>> +
>>   	imx_data->pinctrl = devm_pinctrl_get(&pdev->dev);
>>   	if (IS_ERR(imx_data->pinctrl))
>>   		dev_warn(mmc_dev(host->mmc), "could not get pinctrl\n");
>