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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 7 Apr 2021 14:53:09 +0200
Message-ID: <CAJZ5v0hzbJmTy=X8R60FYqKkmhLama7C_ADWLPQ2k0SuJ4UGeg@mail.gmail.com>
Subject: Re: [PATCH] resource: Prevent irqresource_disabled() from erasing flags
To:     Angela Czubak <acz@semihalf.com>
Cc:     Mika Westerberg <mika.westerberg@linux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        John Garry <john.garry@huawei.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        upstream@semihalf.com, Dmitry Torokhov <dtor@chromium.org>,
        linux-acpi <linux-acpi@intel.com>
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On Wed, Apr 7, 2021 at 1:01 PM Angela Czubak <acz@semihalf.com> wrote:
>
> On Tue, Mar 30, 2021 at 5:50 PM Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
> >
> > Hi,
> >
> > On Tue, Mar 30, 2021 at 05:09:42PM +0200, Rafael J. Wysocki wrote:
> > > On 3/29/2021 9:52 PM, Angela Czubak wrote:
> > > > Do not overwrite flags as it leads to erasing triggering and polarity
> > > > information which might be useful in case of hard-coded interrupts.
> > > > This way the information can be read later on even though mapping to
> > > > APIC domain failed.
> > > >
> > > > Signed-off-by: Angela Czubak <acz@semihalf.com>
> > > > ---
> > > > Some Chromebooks use hard-coded interrupts in their ACPI tables.
> > > > This is an excerpt as dumped on Relm:
> > > >
> > > > ...
> > > >              Name (_HID, "ELAN0001")  // _HID: Hardware ID
> > > >              Name (_DDN, "Elan Touchscreen ")  // _DDN: DOS Device Name
> > > >              Name (_UID, 0x05)  // _UID: Unique ID
> > > >              Name (ISTP, Zero)
> > > >              Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
> > > >              {
> > > >                  Name (BUF0, ResourceTemplate ()
> > > >                  {
> > > >                      I2cSerialBusV2 (0x0010, ControllerInitiated, 0x00061A80,
> > > >                          AddressingMode7Bit, "\\_SB.I2C1",
> > > >                          0x00, ResourceConsumer, , Exclusive,
> > > >                          )
> > > >                      Interrupt (ResourceConsumer, Edge, ActiveLow, Exclusive, ,, )
> > > >                      {
> > > >                          0x000000B8,
> > > >                      }
> > > >                  })
> > > >                  Return (BUF0) /* \_SB_.I2C1.ETSA._CRS.BUF0 */
> > > >              }
> > > > ...
> > > >
> > > > This interrupt is hard-coded to 0xB8 = 184 which is too high to be mapped
> > > > to IO-APIC, so no triggering information is propagated as acpi_register_gsi()
> > > > fails and irqresource_disabled() is issued, which leads to erasing triggering
> > > > and polarity information.
> > > > If that function added its flags instead of overwriting them the correct IRQ
> > > > type would be set even for the hard-coded interrupts, which allows device driver
> > > > to retrieve it.
> > > > Please, let me know if this kind of modification is acceptable.
> > >
> > > From the quick look it should not be problematic, but it needs to be checked
> > > more carefully.
> > >
> > > Mika, what do you think?
> >
> > I think it makes sense. We still set IORESOURCE_DISABLED unconditionally
> > so this should not cause issues. In theory at least :)
> >
> Is there anything else you would need me to do regarding the patch?

Yes, please resend it with a CC to linux-acpi@vger.kernel.org for more
visibility.

> I suppose there are more platforms that could benefit from not erasing
> the flags, so if this patch is fit for upstream, can we continue the
> process?
>
> > > >   include/linux/ioport.h | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> > > > index 55de385c839cf..647744d8514e0 100644
> > > > --- a/include/linux/ioport.h
> > > > +++ b/include/linux/ioport.h
> > > > @@ -331,7 +331,7 @@ static inline void irqresource_disabled(struct resource *res, u32 irq)
> > > >   {
> > > >     res->start = irq;
> > > >     res->end = irq;
> > > > -   res->flags = IORESOURCE_IRQ | IORESOURCE_DISABLED | IORESOURCE_UNSET;
> > > > +   res->flags |= IORESOURCE_IRQ | IORESOURCE_DISABLED | IORESOURCE_UNSET;
> > > >   }
> > > >   extern struct address_space *iomem_get_mapping(void);
> > >