From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Date: Thu, 17 Sep 2020 02:32:10 +0000 Subject: Re: [PATCH] PM / devfreq: tegra30: disable clock on error in probe Message-Id: <8edcfd7b-110b-3886-64ee-3ec02cc6bd19@samsung.com> List-Id: References: <20200908072557.GC294938@mwanda> <2ceb045a-ebac-58d7-0250-4ea39d711ce8@samsung.com> <44560522-f04e-ade5-2e02-9df56a6f79ba@gmail.com> <2573cd77-1175-d194-7bfc-24d28b276846@samsung.com> <5aac4d59-5e06-25a6-3de1-6a5a586b9e34@gmail.com> <887f4b2d-9181-356c-5f09-23be30d2480c@gmail.com> In-Reply-To: <887f4b2d-9181-356c-5f09-23be30d2480c@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Dmitry Osipenko , Dan Carpenter Cc: MyungJoo Ham , Kyungmin Park , Thierry Reding , Jonathan Hunter , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, kernel-janitors@vger.kernel.org On 9/17/20 4:07 AM, Dmitry Osipenko wrote: > 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 >>>>>>>> --- >>>>>>>> --- >>>>>>>> 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. > Thanks for the detailed explanation. But, I think that almost people don't know the detailed h/w information. If possible, how about matching the pair when clk-enable fails as following? --- a/drivers/devfreq/tegra30-devfreq.c +++ b/drivers/devfreq/tegra30-devfreq.c @@ -828,6 +828,7 @@ static int tegra_devfreq_probe(struct platform_device *pdev) if (err) { dev_err(&pdev->dev, "Failed to prepare and enable ACTMON clock\n"); + reset_control_deassert(tegra->reset); return err; } -- Best Regards, Chanwoo Choi Samsung Electronics