On Thu, Mar 17, 2016 at 03:04:01PM +0000, Jon Hunter wrote: > > On 17/03/16 14:51, Thomas Gleixner wrote: > > On Thu, 17 Mar 2016, 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 we should only fail to set the > >> type for PPIs whose configuration cannot be changed anyway, don't return > >> an error and simply WARN if this fails. This will allows us to fix up any > >> places in the kernel where we should be checking the return status and > >> maintain back compatibility with firmware images that may have incorrect > >> interrupt configurations. > > > > Though silently returning 0 is really the wrong thing to do. You can add the > > warn, but why do you want to return success? > > Yes that would be the correct thing to do I agree. However, the problem > is that if we do this, then after the patch "irqdomain: Don't set type > when mapping an IRQ" is applied, we may break interrupts for some > existing device-tree binaries that have bad configuration (such as omap4 > and tegra20/30 ... see patches 1 and 2) that have gone unnoticed. So it > is a back compatibility issue. This sounds like a textbook case for adding a boolean dt property. If "can-set-ppi-type" is absent (old DT blobs and new blobs without the ability), warn and return zero. If it's present, the driver can set the type, returning errors as encountered. thx, Jason. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
