Re: [PATCH] PM / devfreq: tegra30: disable clock on error in probe

[Dmitry Osipenko <digetx@gmail.com>]

16.09.2020 05:38, Chanwoo Choi пишет:
> On 9/16/20 2:01 AM, Dmitry Osipenko wrote:
>> 15.09.2020 05:13, Chanwoo Choi пишет:
>>> On 9/15/20 11:00 AM, Chanwoo Choi wrote:
>>>> Hi Dmitry,
>>>>
>>>> On 9/14/20 10:56 PM, Dmitry Osipenko wrote:
>>>>> 14.09.2020 10:09, Chanwoo Choi пишет:
>>>>>> Hi,
>>>>>>
>>>>>> On 9/8/20 4:25 PM, Dan Carpenter wrote:
>>>>>>> This error path needs to call clk_disable_unprepare().
>>>>>>>
>>>>>>> Fixes: 7296443b900e ("PM / devfreq: tegra30: Handle possible round-rate error")
>>>>>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>>>>> ---
>>>>>>> ---
>>>>>>>  drivers/devfreq/tegra30-devfreq.c | 4 +++-
>>>>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
>>>>>>> index e94a27804c20..dedd39de7367 100644
>>>>>>> --- a/drivers/devfreq/tegra30-devfreq.c
>>>>>>> +++ b/drivers/devfreq/tegra30-devfreq.c
>>>>>>> @@ -836,7 +836,8 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>>>>>>>  	rate = clk_round_rate(tegra->emc_clock, ULONG_MAX);
>>>>>>>  	if (rate < 0) {
>>>>>>>  		dev_err(&pdev->dev, "Failed to round clock rate: %ld\n", rate);
>>>>>>> -		return rate;
>>>>>>> +		err = rate;
>>>>>>> +		goto disable_clk;
>>>>>>>  	}
>>>>>>>  
>>>>>>>  	tegra->max_freq = rate / KHZ;
>>>>>>> @@ -897,6 +898,7 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
>>>>>>>  	dev_pm_opp_remove_all_dynamic(&pdev->dev);
>>>>>>>  
>>>>>>>  	reset_control_reset(tegra->reset);
>>>>>>> +disable_clk:
>>>>>>>  	clk_disable_unprepare(tegra->clock);
>>>>>>
>>>>>> Is it doesn't need to reset with reset_contrl_reset()?
>>>>>
>>>>> Hello, Chanwoo!
>>>>>
>>>>> It's reset just before the clk_round_rate() invocation, hence there
>>>>> shouldn't be a need to reset it second time.
>>>>
>>>> Do you mean that reset is deasserted automatically
>>>> when invoke clk_round_rate() on tegra?
>>
>> I only mean that the tegra30-devfreq driver deasserts the reset before
>> the clk_round_rate():
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/devfreq/tegra30-devfreq.c?h=v5.9-rc5#n834
>>
>>>> If tree, I think that 'reset_control_reset(tegra->reset)' invocation
>>>
>>> I'm sorry for my typo. s/tree/true.
>>>
>>>> is not needed on 'remove_opp:' goto. Because already reset deassertion
>>>> is invoked by clk_round_rate(), it seems that doesn't need to invoke
>>>> anymore during exception case.
>>>>
>>>> Actually, it is not clear in my case.
>>
>> The reset_control_reset() in the error path of the driver probe function
>> is placed that way to make the tear-down order match the driver removal
>> order. Perhaps the reset could be moved before the remove_opp, but this
>> change won't make any real difference, hence it already should be good
>> as-is.
>>
>>
> 
> I have one more question.
> When failed to enable clock on line829[1],
> does it need any reset_control invocation?
> In this case on line829, just return without any restoration 
> about reset control.
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/devfreq/tegra30-devfreq.c?h=v5.9-rc5#n829
> 

There is no need to deassert the reset if clk-enable fails because reset
control of tegra30-devfreq is exclusive, i.e it isn't shared with any
other peripherals, and thus, reset control could asserted/deasserted at
any time by the devfreq driver. If clk-enable fails, then reset will
stay asserted and it will be fine to re-assert it again.