Patchwork [v2,03/19] PM / devfreq: tegra: Don't ignore clk errors

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Submitter Dmitry Osipenko
Date April 15, 2019, 2:54 p.m.
Message ID <20190415145505.18397-4-digetx@gmail.com>
Download mbox | patch
Permalink /patch/773269/
State New
Headers show

Comments

Dmitry Osipenko - April 15, 2019, 2:54 p.m.
The clk_set_min_rate() could fail and in this case clk_set_rate() sets
rate to 0, which may drop EMC rate to minimum and make machine very
difficult to use.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/devfreq/tegra-devfreq.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
Chanwoo Choi - April 16, 2019, 1:52 a.m.
Hi,

On 19. 4. 15. 오후 11:54, Dmitry Osipenko wrote:
> The clk_set_min_rate() could fail and in this case clk_set_rate() sets
> rate to 0, which may drop EMC rate to minimum and make machine very
> difficult to use.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/devfreq/tegra-devfreq.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index 0c0909fba545..69581c9082d4 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -487,6 +487,7 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>  	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
>  	struct dev_pm_opp *opp;
>  	unsigned long rate;
> +	int err;
>  
>  	opp = devfreq_recommended_opp(dev, freq, flags);
>  	if (IS_ERR(opp)) {
> @@ -496,8 +497,13 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>  	rate = dev_pm_opp_get_freq(opp);
>  	dev_pm_opp_put(opp);
>  
> -	clk_set_min_rate(tegra->emc_clock, rate);
> -	clk_set_rate(tegra->emc_clock, 0);
> +	err = clk_set_min_rate(tegra->emc_clock, rate);
> +	if (err)
> +		return err;
> +
> +	err = clk_set_rate(tegra->emc_clock, 0);
> +	if (err)

Why don't you restore the previous minimum clock for tegra->emc_clock
when failed to execute 'clk_set_rate(tegra->emc_clock, 0);'?

I think that if you control the restoring the previous minimum clock,
it is more nice to handle the error handling.

> +		return err;
>  
>  	return 0;
>  }
>
Dmitry Osipenko - April 16, 2019, 1:42 p.m.
16.04.2019 4:52, Chanwoo Choi пишет:
> Hi,
> 
> On 19. 4. 15. 오후 11:54, Dmitry Osipenko wrote:
>> The clk_set_min_rate() could fail and in this case clk_set_rate() sets
>> rate to 0, which may drop EMC rate to minimum and make machine very
>> difficult to use.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  drivers/devfreq/tegra-devfreq.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
>> index 0c0909fba545..69581c9082d4 100644
>> --- a/drivers/devfreq/tegra-devfreq.c
>> +++ b/drivers/devfreq/tegra-devfreq.c
>> @@ -487,6 +487,7 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>>  	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
>>  	struct dev_pm_opp *opp;
>>  	unsigned long rate;
>> +	int err;
>>  
>>  	opp = devfreq_recommended_opp(dev, freq, flags);
>>  	if (IS_ERR(opp)) {
>> @@ -496,8 +497,13 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
>>  	rate = dev_pm_opp_get_freq(opp);
>>  	dev_pm_opp_put(opp);
>>  
>> -	clk_set_min_rate(tegra->emc_clock, rate);
>> -	clk_set_rate(tegra->emc_clock, 0);
>> +	err = clk_set_min_rate(tegra->emc_clock, rate);
>> +	if (err)
>> +		return err;
>> +
>> +	err = clk_set_rate(tegra->emc_clock, 0);
>> +	if (err)
> 
> Why don't you restore the previous minimum clock for tegra->emc_clock
> when failed to execute 'clk_set_rate(tegra->emc_clock, 0);'?
> 
> I think that if you control the restoring the previous minimum clock,
> it is more nice to handle the error handling.

I now see that devfreq has the previous_freq field and indeed it is possible to restore the min_rate value using it. Thanks for the suggestion.

Patch

diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
index 0c0909fba545..69581c9082d4 100644
--- a/drivers/devfreq/tegra-devfreq.c
+++ b/drivers/devfreq/tegra-devfreq.c
@@ -487,6 +487,7 @@  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
 	struct tegra_devfreq *tegra = dev_get_drvdata(dev);
 	struct dev_pm_opp *opp;
 	unsigned long rate;
+	int err;
 
 	opp = devfreq_recommended_opp(dev, freq, flags);
 	if (IS_ERR(opp)) {
@@ -496,8 +497,13 @@  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
 	rate = dev_pm_opp_get_freq(opp);
 	dev_pm_opp_put(opp);
 
-	clk_set_min_rate(tegra->emc_clock, rate);
-	clk_set_rate(tegra->emc_clock, 0);
+	err = clk_set_min_rate(tegra->emc_clock, rate);
+	if (err)
+		return err;
+
+	err = clk_set_rate(tegra->emc_clock, 0);
+	if (err)
+		return err;
 
 	return 0;
 }