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

From: Dmitry Osipenko <digetx@gmail.com>
To: Chanwoo Choi <cw00.choi@samsung.com>,
	Dan Carpenter <dan.carpenter@oracle.com>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] PM / devfreq: tegra30: disable clock on error in probe
Date: Tue, 15 Sep 2020 20:01:12 +0300	[thread overview]
Message-ID: <5aac4d59-5e06-25a6-3de1-6a5a586b9e34@gmail.com> (raw)
In-Reply-To: <2573cd77-1175-d194-7bfc-24d28b276846@samsung.com>

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.