Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails

From	Jon Hunter <jonathanh@nvidia.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails
Date	2016-03-17 17:30 +0100
Message-ID	<rdIYa-1i1-15@gated-at.bofh.it> (permalink)
References	<rdGWl-8uZ-9@gated-at.bofh.it> <rdH63-6P-35@gated-at.bofh.it> <rdHz3-gE-5@gated-at.bofh.it> <rdHIJ-zS-5@gated-at.bofh.it> <rdHSq-Dd-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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.
> 
> 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.

Please note that gic_configure_irq() never used to return an error and
only when adding support for setting the type of PPIs was this added.
However, given that this has gone unnoticed and does not have a real
functional impact on the device behaviour, I wonder now if this function
should return an error? Yes, ideally, it should, but does it still make
sense?

Cheers
Jon

Thread

[PATCH 00/15] Add support for Tegra210 AGIC Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 05/15] irqchip: Mask the non-type/sense bits when translating an IRQ Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 09/15] irqchip/gic: Don't initialise chip if mapping IO space fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 02/15] ARM: OMAP: Correct interrupt type for ARM TWD Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 02/15] ARM: OMAP: Correct interrupt type for ARM TWD Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 16:50 +0100
      Re: [PATCH 02/15] ARM: OMAP: Correct interrupt type for ARM TWD Jon Hunter <jonathanh@nvidia.com> - 2016-03-29 16:10 +0200
        Re: [PATCH 02/15] ARM: OMAP: Correct interrupt type for ARM TWD Tony Lindgren <tony@atomide.com> - 2016-03-30 23:30 +0200
  [PATCH 10/15] irqchip/gic: Remove static irq_chip definition for eoimode1 Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 10/15] irqchip/gic: Remove static irq_chip definition for eoimode1 Linus Walleij <linus.walleij@linaro.org> - 2016-03-22 12:50 +0100
  [PATCH 08/15] genirq: Add runtime power management support for IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Marc Zyngier <marc.zyngier@arm.com> - 2016-03-17 16:10 +0100
      Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 16:20 +0100
        Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Marc Zyngier <marc.zyngier@arm.com> - 2016-03-17 16:30 +0100
          Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Linus Walleij <linus.walleij@linaro.org> - 2016-03-22 12:50 +0100
    Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Thomas Gleixner <tglx@linutronix.de> - 2016-03-17 16:10 +0100
      Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 16:50 +0100
    Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 12:20 +0100
      Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 13:30 +0100
        Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 15:30 +0100
          Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 15:50 +0100
            Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 16:00 +0100
              Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 19:00 +0100
                Re: [PATCH 08/15] genirq: Add runtime power management support for  IRQ chips Jon Hunter <jonathanh@nvidia.com> - 2016-03-21 11:10 +0100
  [PATCH 12/15] irqchip/gic: Pass GIC pointer to save/restore functions Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 13/15] irqchip/gic: Prepare for adding platform driver Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 13/15] irqchip/gic: Prepare for adding platform driver Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-29 15:10 +0200
      Re: [PATCH 13/15] irqchip/gic: Prepare for adding platform driver Jon Hunter <jonathanh@nvidia.com> - 2016-03-29 16:00 +0200
  [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type  fails Thomas Gleixner <tglx@linutronix.de> - 2016-03-17 16:00 +0100
      Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type  fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 16:10 +0100
        Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type  fails Jason Cooper <jason@lakedaemon.net> - 2016-03-17 16:20 +0100
          Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type  fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 17:30 +0100
            Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 10:30 +0100
              Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type  fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 11:00 +0100
                Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 11:30 +0100
  [PATCH 03/15] irqchip/gic: Don't unnecessarily write the IRQ configuration Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from binding document Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
    Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Rob Herring <robh+dt@kernel.org> - 2016-03-17 21:20 +0100
      Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 09:40 +0100
    Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 10:20 +0100
      Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 11:20 +0100
        Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 12:00 +0100
          Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 12:00 +0100
            Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 13:10 +0100
              Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 13:50 +0100
                Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Geert Uytterhoeven <geert@linux-m68k.org> - 2016-03-18 14:10 +0100
                Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Grygorii Strashko <grygorii.strashko@ti.com> - 2016-03-18 19:40 +0100
              Re: [PATCH 14/15] dt-bindings: arm-gic: Drop 'clock-names' from  binding document Jon Hunter <jonathanh@nvidia.com> - 2016-03-18 13:50 +0100
  [PATCH 11/15] irqchip/gic: Return an error if GIC initialisation fails Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100
  [PATCH 15/15] irqchip/gic: Add support for tegra AGIC interrupt controller Jon Hunter <jonathanh@nvidia.com> - 2016-03-17 15:30 +0100

csiph-web