From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH v4 07/16] PM / devfreq: tegra: Properly disable interrupts Date: Fri, 7 Jun 2019 19:58:20 +0300 Message-ID: <7be61b38-62c7-8536-a102-36f5ac6668e2@gmail.com> References: <20190501233815.32643-1-digetx@gmail.com> <20190501233815.32643-8-digetx@gmail.com> <20190604110744.GG16519@ulmo> <2b09a162-a090-901b-01cf-46b116a87a7a@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <2b09a162-a090-901b-01cf-46b116a87a7a@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding , MyungJoo Ham Cc: Jonathan Hunter , Kyungmin Park , Chanwoo Choi , Tomeu Vizoso , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-tegra@vger.kernel.org 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 >>>> Signed-off-by: Dmitry Osipenko >>>> --- >>>> 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!