From: Dmitry Osipenko <digetx@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>,
MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Chanwoo Choi <cw00.choi@samsung.com>,
Tomeu Vizoso <tomeu.vizoso@collabora.com>,
linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 07/16] PM / devfreq: tegra: Properly disable interrupts
Date: Fri, 7 Jun 2019 19:58:20 +0300 [thread overview]
Message-ID: <7be61b38-62c7-8536-a102-36f5ac6668e2@gmail.com> (raw)
In-Reply-To: <2b09a162-a090-901b-01cf-46b116a87a7a@gmail.com>
05.06.2019 1:55, Dmitry Osipenko пишет:
> 04.06.2019 16:40, Dmitry Osipenko пишет:
>> 04.06.2019 14:07, Thierry Reding пишет:
>>> On Thu, May 02, 2019 at 02:38:06AM +0300, Dmitry Osipenko wrote:
>>>> There is no guarantee that interrupt handling isn't running in parallel
>>>> with tegra_actmon_disable_interrupts(), hence it is necessary to protect
>>>> DEV_CTRL register accesses and clear IRQ status with ACTMON's IRQ being
>>>> disabled in the Interrupt Controller in order to ensure that device
>>>> interrupt is indeed being disabled.
>>>>
>>>> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>>> ---
>>>> drivers/devfreq/tegra-devfreq.c | 21 +++++++++++++++------
>>>> 1 file changed, 15 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
>>>> index b65313fe3c2e..ce1eb97a2090 100644
>>>> --- a/drivers/devfreq/tegra-devfreq.c
>>>> +++ b/drivers/devfreq/tegra-devfreq.c
>>>> @@ -171,6 +171,8 @@ struct tegra_devfreq {
>>>> struct notifier_block rate_change_nb;
>>>>
>>>> struct tegra_devfreq_device devices[ARRAY_SIZE(actmon_device_configs)];
>>>> +
>>>> + int irq;
>>>
>>> Interrupts are typically unsigned int.
>>>
>>>> };
>>>>
>>>> struct tegra_actmon_emc_ratio {
>>>> @@ -417,6 +419,8 @@ static void tegra_actmon_disable_interrupts(struct tegra_devfreq *tegra)
>>>> u32 val;
>>>> unsigned int i;
>>>>
>>>> + disable_irq(tegra->irq);
>>>> +
>>>> for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
>>>> dev = &tegra->devices[i];
>>>>
>>>> @@ -427,9 +431,14 @@ static void tegra_actmon_disable_interrupts(struct tegra_devfreq *tegra)
>>>> val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
>>>>
>>>> device_writel(dev, val, ACTMON_DEV_CTRL);
>>>> +
>>>> + device_writel(dev, ACTMON_INTR_STATUS_CLEAR,
>>>> + ACTMON_DEV_INTR_STATUS);
>>>> }
>>>>
>>>> actmon_write_barrier(tegra);
>>>> +
>>>> + enable_irq(tegra->irq);
>>>
>>> Why do we enable interrupts after this? Is there any use in having the
>>> top-level interrupt enabled if nothing's going to generate an interrupt
>>> anyway?
>>
>> There is no real point in having the interrupt enabled other than to
>> keep the enable count balanced.
>>
>> IIUC, we will need to disable IRQ at the driver's probe time (after
>> requesting the IRQ) if we want to avoid that (not really necessary)
>> balancing. This is probably something that could be improved in a
>> follow-up patches, if desired.
>
> Nah, it's not worth the effort. It is quite problematic that we can't
> keep interrupt disabled during of devfreq_add_device() execution because
> it asks governor to enable the interrupt and the interrupt shall be
> disabled because we're using device's lock in the governor interrupt
> handler.. device is getting assigned only after completion of the
> devfreq_add_device() and hence ISR gets a NULL deref if it is fired
> before device is assigned. So I'll leave this part as-is.
>
> Thierry, please answer to all of the remaining patches where you had
> some concerns. I'll send out another series on top of this, addressing
> yours comments and fixing another bug that I spotted today.
>
I looked at this once again and found that the interrupt could be kept
disabled on request using the IRQ_NOAUTOEN flag and then the device
could be assigned within the governor's event handler, so everything is
resolved very nicely! :)
I'll send patches addressing this comment and the rest after getting
relies from you guys. Please try to not postpone the responses too much
as more interactivity in a review/apply process usually help quite a
lot, thanks in advance!
next prev parent reply other threads:[~2019-06-07 16:58 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190501234148epcas5p1cc9a8dafa9ee6d8d046d1292b8270727@epcas5p1.samsung.com>
2019-05-01 23:37 ` [PATCH v4 00/16] NVIDIA Tegra devfreq improvements and Tegra20/30 support Dmitry Osipenko
2019-05-01 23:37 ` Dmitry Osipenko
2019-05-01 23:38 ` [PATCH v4 01/16] PM / devfreq: tegra: Fix kHz to Hz conversion Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 10:54 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 02/16] PM / devfreq: tegra: Replace readl-writel with relaxed versions Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 10:55 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 03/16] PM / devfreq: tegra: Replace write memory barrier with the read barrier Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 10:56 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 04/16] PM / devfreq: tegra: Don't ignore clk errors Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 10:57 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 05/16] PM / devfreq: tegra: Don't set EMC clock rate to maximum on probe Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:00 ` Thierry Reding
2019-06-04 13:05 ` Dmitry Osipenko
2019-05-01 23:38 ` [PATCH v4 06/16] PM / devfreq: tegra: Drop primary interrupt handler Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:02 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 07/16] PM / devfreq: tegra: Properly disable interrupts Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:07 ` Thierry Reding
2019-06-04 13:40 ` Dmitry Osipenko
2019-06-04 14:06 ` Thierry Reding
2019-06-04 14:59 ` Dmitry Osipenko
2019-06-04 22:55 ` Dmitry Osipenko
2019-06-07 16:58 ` Dmitry Osipenko [this message]
2019-05-01 23:38 ` [PATCH v4 08/16] PM / devfreq: tegra: Clean up driver's probe / remove Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:09 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 09/16] PM / devfreq: tegra: Avoid inconsistency of current frequency value Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:14 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 10/16] PM / devfreq: tegra: Mark ACTMON's governor as immutable Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:15 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 11/16] PM / devfreq: tegra: Move governor registration to driver's probe Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:15 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 12/16] PM / devfreq: tegra: Reconfigure hardware on governor's restart Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:17 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 13/16] PM / devfreq: tegra: Support Tegra30 Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:18 ` Thierry Reding
2019-05-01 23:38 ` [PATCH v4 14/16] PM / devfreq: tegra: Enable COMPILE_TEST for the driver Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:20 ` Thierry Reding
2019-06-04 13:53 ` Dmitry Osipenko
2019-06-04 14:10 ` Thierry Reding
2019-06-04 14:18 ` Thierry Reding
2019-06-04 14:41 ` Dmitry Osipenko
2019-06-04 14:50 ` Thierry Reding
2019-06-04 15:15 ` Dmitry Osipenko
2019-05-01 23:38 ` [PATCH v4 15/16] PM / devfreq: tegra: Rename tegra-devfreq.c to tegra30-devfreq.c Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:23 ` Thierry Reding
2019-06-04 14:35 ` Dmitry Osipenko
2019-05-01 23:38 ` [PATCH v4 16/16] PM / devfreq: Introduce driver for NVIDIA Tegra20 Dmitry Osipenko
2019-05-01 23:38 ` Dmitry Osipenko
2019-06-04 11:25 ` Thierry Reding
2019-06-04 13:57 ` Dmitry Osipenko
2019-05-03 0:31 ` [PATCH v4 00/16] NVIDIA Tegra devfreq improvements and Tegra20/30 support Chanwoo Choi
2019-05-03 0:31 ` Chanwoo Choi
2019-05-03 0:52 ` Dmitry Osipenko
2019-05-03 0:52 ` Dmitry Osipenko
2019-06-03 16:52 ` Dmitry Osipenko
2019-06-04 0:49 ` Chanwoo Choi
2019-06-04 23:09 ` Dmitry Osipenko
2019-06-23 17:17 ` Dmitry Osipenko
2019-06-23 23:50 ` Chanwoo Choi
2019-06-24 0:35 ` Dmitry Osipenko
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