04.06.2019 17:06, Thierry Reding пишет: > On Tue, Jun 04, 2019 at 04:40:18PM +0300, Dmitry Osipenko wrote: >> 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 <[email protected]> >>>> Signed-off-by: Dmitry Osipenko <[email protected]> >>>> --- >>>> 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. >> >>>> } >>>> >>>> static void tegra_actmon_configure_device(struct tegra_devfreq *tegra, >>>> @@ -604,7 +613,6 @@ static int tegra_devfreq_probe(struct platform_device >>>> *pdev) >>>> struct resource *res; >>>> unsigned int i; >>>> unsigned long rate; >>>> - int irq; >>>> int err; >>>> >>>> tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL); >>>> @@ -673,15 +681,16 @@ static int tegra_devfreq_probe(struct >>>> platform_device *pdev) >>>> dev_pm_opp_add(&pdev->dev, rate, 0); >>>> } >>>> >>>> - irq = platform_get_irq(pdev, 0); >>>> - if (irq < 0) { >>>> - dev_err(&pdev->dev, "Failed to get IRQ: %d\n", irq); >>>> - return irq; >>>> + tegra->irq = platform_get_irq(pdev, 0); >>>> + if (tegra->irq < 0) { >>>> + err = tegra->irq; >>>> + dev_err(&pdev->dev, "Failed to get IRQ: %d\n", err); >>>> + return err; >>>> } >>> >>> This is very oddly written. tegra->irq should really be an unsigned int >>> since that's the standard type for interrupt numbers. But since you need >>> to be able to detect errors from platform_get_irq() it now becomes >>> natural to write this as: >>> >>> err = platform_get_irq(pdev, 0); >>> if (err < 0) { >>> dev_err(...); >>> return err; >>> } >>> >>> tegra->irq = err; >>> >>> Two birds with one stone. I suppose this could be done in a follow-up >>> patch since it isn't practically wrong in your version, so either way: >>> >>> Acked-by: Thierry Reding <[email protected]> >>> >> >> Thank you for the ACK! Although, I disagree with yours suggestion, to me >> that makes code a bit less straightforward and it's not really >> worthwhile to bloat the code just because technically IRQ's are unsigned >> numbers (we don't care about that). It also makes me a bit uncomfortable >> to see "err" assigned to a variable, I don't think it's a good practice. > > Actually you should care that IRQs are unsigned. Implicit casting from > a potentially negative value can hide bugs. That is, once you've passed > that negative value into the IRQ API you loose the context that it could > be an error code. Hence I think it makes sense to always store values in > the native type, and only store them if they are actually valid. > > In the above you have an error value in tegra->irq. In this particular > case it's pretty harmless because you don't do anything with it, but if > the circumstances were slightly different that could lead to problems > down the road. > > On the other hand what I was proposing makes it pretty clear from the > context that err contains a valid interrupt number when it is assigned > to tegra->irq. There's plenty of similar constructs in the kernel if you > want to grep for it. > > Also, it's not bloating the code at all. It's the exact same number of > lines of code as your variant.
I agree that it is better to maintain proper typing everywhere in general, I have been bitten so many times by typecasting bugs.. Opentegra's Bool (unsigned) -> BOOL (signed) casting horror was the most recent one. Well, I guess indeed it won't hurt to apply your suggestion in a follow-up patch to keep things a bit more consistent.
