linux-kernel - Re: [PATCH] usb: dwc3-exynos fix unspecified suspend clk error handling

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Message-ID: <2e4a5e53-6603-13b8-0302-dc8093978013@osg.samsung.com>
Date:   Tue, 10 Jan 2017 07:16:21 -0700
From:   Shuah Khan <shuahkh@....samsung.com>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     balbi@...nel.org, gregkh@...uxfoundation.org, kgene@...nel.org,
        krzk@...nel.org, javier@....samsung.com,
        linux-samsung-soc@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH] usb: dwc3-exynos fix unspecified suspend clk error
 handling

On 01/10/2017 05:05 AM, Bartlomiej Zolnierkiewicz wrote:
> 
> Hi,
> 
> On Monday, January 09, 2017 07:21:31 PM Shuah Khan wrote:
>> Fix dwc3_exynos_probe() to call clk_prepare_enable() only when suspend
>> clock is specified. Call clk_disable_unprepare() from remove and probe
>> error path only when susp_clk has been set from remove and probe error
>> paths.
> 
> It is legal to call clk_prepare_enable() and clk_disable_unprepare()
> for NULL clock.  Also your patch changes susp_clk handling while
> leaves axius_clk handling (which also can be NULL) untouched.
> 
> Do you actually see some runtime problem with the current code?
> 
> If not then the patch should probably be dropped.
> 
> Best regards,
> --
> Bartlomiej Zolnierkiewicz
> Samsung R&D Institute Poland
> Samsung Electronics

Hi Bartlomiej,

I am seeing the "no suspend clk specified" message in dmesg.
After that it sets the exynos->susp_clk = NULL and starts
calling clk_prepare_enable(exynos->susp_clk);

That can't be good. If you see the logic right above this
one for exynos->clk, it returns error and fails the probe.
This this case it doesn't, but tries to use null susp_clk.

I believe this patch is necessary.

thanks,
-- Shuah

> 
>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
>> ---
>>  drivers/usb/dwc3/dwc3-exynos.c | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
>> index e27899b..f97a3d7 100644
>> --- a/drivers/usb/dwc3/dwc3-exynos.c
>> +++ b/drivers/usb/dwc3/dwc3-exynos.c
>> @@ -131,8 +131,8 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
>>  	if (IS_ERR(exynos->susp_clk)) {
>>  		dev_info(dev, "no suspend clk specified\n");
>>  		exynos->susp_clk = NULL;
>> -	}
>> -	clk_prepare_enable(exynos->susp_clk);
>> +	} else
>> +		clk_prepare_enable(exynos->susp_clk);
>>  
>>  	if (of_device_is_compatible(node, "samsung,exynos7-dwusb3")) {
>>  		exynos->axius_clk = devm_clk_get(dev, "usbdrd30_axius_clk");
>> @@ -196,7 +196,8 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
>>  	regulator_disable(exynos->vdd33);
>>  err2:
>>  	clk_disable_unprepare(exynos->axius_clk);
>> -	clk_disable_unprepare(exynos->susp_clk);
>> +	if (exynos->susp_clk)
>> +		clk_disable_unprepare(exynos->susp_clk);
>>  	clk_disable_unprepare(exynos->clk);
>>  	return ret;
>>  }
>> @@ -210,7 +211,8 @@ static int dwc3_exynos_remove(struct platform_device *pdev)
>>  	platform_device_unregister(exynos->usb3_phy);
>>  
>>  	clk_disable_unprepare(exynos->axius_clk);
>> -	clk_disable_unprepare(exynos->susp_clk);
>> +	if (exynos->susp_clk)
>> +		clk_disable_unprepare(exynos->susp_clk);
>>  	clk_disable_unprepare(exynos->clk);
>>  
>>  	regulator_disable(exynos->vdd33);
>