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 <a...@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 :)
> > 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);
>
