From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Date: Wed, 16 Sep 2020 19:07:46 +0000 Subject: Re: [PATCH] PM / devfreq: tegra30: disable clock on error in probe Message-Id: <887f4b2d-9181-356c-5f09-23be30d2480c@gmail.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> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Chanwoo Choi , 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 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.