From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [PATCH V3 02/17] irqchip/gic: WARN if setting the interrupt type for a PPI fails Date: Thu, 5 May 2016 13:06:09 +0100 Message-ID: <572B3731.80602@arm.com> References: <1462379130-11742-1-git-send-email-jonathanh@nvidia.com> <1462379130-11742-3-git-send-email-jonathanh@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1462379130-11742-3-git-send-email-jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jon Hunter , Thomas Gleixner , Jason Cooper , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Stephen Warren , Thierry Reding Cc: Kevin Hilman , Geert Uytterhoeven , Grygorii Strashko , Lars-Peter Clausen , Linus Walleij , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-omap@vger.kernel.org Hi Jon, On 04/05/16 17:25, Jon Hunter wrote: > Setting the interrupt type for private peripheral interrupts (PPIs) may > not be supported by a given GIC because it is IMPLEMENTATION DEFINED > whether this is allowed. There is no way to know if setting the type is > supported for a given GIC and so the value written is read back to > verify it matches the desired configuration. If it does not match then > an error is return. > > There are cases where the interrupt configuration read from firmware > (such as a device-tree blob), has been incorrect and hence > gic_configure_irq() has returned an error. This error has gone > undetected because the error code returned was ignored but the interrupt > still worked fine because the configuration for the interrupt could not > be overwritten. > > Given that this has done undetected and that failing to set the > configuration for a PPI may not be a catastrophic, don't return an error > but WARN if we fail to configure a PPI. This will allows us to fix up > any places in the kernel where we should be checking the return status > and maintain backward compatibility with firmware images that may have > incorrect PPI configurations. > > Signed-off-by: Jon Hunter > Acked-by: Marc Zyngier > --- > drivers/irqchip/irq-gic-common.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c > index ffff5a45f1e3..9fa92a17225c 100644 > --- a/drivers/irqchip/irq-gic-common.c > +++ b/drivers/irqchip/irq-gic-common.c > @@ -56,12 +56,15 @@ int gic_configure_irq(unsigned int irq, unsigned int type, > > /* > * Write back the new configuration, and possibly re-enable > - * the interrupt. If we fail to write a new configuration, > - * return an error. > + * the interrupt. WARN if we fail to write a new configuration > + * and return an error if we failed to write the configuration > + * for an SPI. If we fail to write the configuration for a PPI > + * this is most likely because the GIC does not allow us to set > + * the configuration and so it is not a catastrophic failure. > */ > writel_relaxed(val, base + GIC_DIST_CONFIG + confoff); > - if (readl_relaxed(base + GIC_DIST_CONFIG + confoff) != val) > - ret = -EINVAL; > + if (WARN_ON(readl_relaxed(base + GIC_DIST_CONFIG + confoff) != val)) > + ret = irq < 32 ? 0 : -EINVAL; > > if (sync_access) > sync_access(); > I'm going to slightly backpedal on that one: When running in non-secure mode, you can reconfigure secure interrupts (for obvious reasons). But you don't know which mode you're running in either. A typical example is the arch timer, which requests both secure and non-secure interrupts, because we cannot know which side of the CPU we're running on. In the non-secure case, we end-up with a splat that is rather undeserved. So I'm tempted to tone down the splat in the PPI case like this: diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c index 083c303..1605e42 100644 --- a/drivers/irqchip/irq-gic-common.c +++ b/drivers/irqchip/irq-gic-common.c @@ -63,8 +63,17 @@ int gic_configure_irq(unsigned int irq, unsigned int type, * the configuration and so it is not a catastrophic failure. */ writel_relaxed(val, base + GIC_DIST_CONFIG + confoff); - if (WARN_ON(readl_relaxed(base + GIC_DIST_CONFIG + confoff) != val)) - ret = irq < 32 ? 0 : -EINVAL; + oldval = readl_relaxed(base + GIC_DIST_CONFIG + confoff); + if (oldval != val) { + if (irq < 32) { + pr_warn("GIC: PPI%d is either secure or misconfigured\n", + irq - 16); + ret = 0; + } else { + WARN_ON(1); + ret = -EINVAL; + } + } if (sync_access) sync_access(); Thoughts? M. -- Jazz is not dead. It just smells funny...