On 18/03/16 09:20, Geert Uytterhoeven wrote: > On Thu, Mar 17, 2016 at 5:20 PM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >> On 17/03/16 15:18, Jason Cooper wrote: >>> 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. > > Indeed (also for sh73a0 and r8a7779). Thanks. I was wondering if there are others. Do you know what the correct setting should be? Ie. should it be IRQ_TYPE_EDGE_RISING as well? I can then include this with OMAP and Tegra. >>> 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. >> >> True. However, if we did have this "can-set-ppi-type" property set for a >> device, it really should never fail (unless someone specified it >> incorrectly). So I am trying to understand the value in adding a new DT >> property. > > Do we really want to add properties that basically indicate that a description > in DT is correct? > > Alternatively, it can be fixed in the kernel in a DT quirk (if SoC == xxx then > fix TWD). I am not sure I fully understand your proposal, but please note that it may not be just limited to the TWD (although this does appear to be the one client that is wrong for a lot of SoCs). PPIs are also used for the armv7/8 timers as well. The problem is that we have a lot of SoCs with twd-timers and I have no way to test all of these to know which could be a problem. So I thought that warning would be a good first step to fixing them. However, I am still trying to see the real value in returning an error in this case. May be I am the only one with that perspective? Cheers Jon
