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    SubjectRe: [PATCH V3 02/17] irqchip/gic: WARN if setting the interrupt type for a PPI fails
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    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 <jonathanh@nvidia.com>
    > Acked-by: Marc Zyngier <marc.zyngier@arm.com>
    > ---
    > 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...

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