On Thu, Apr 8, 2021 at 12:38 PM Angela Czubak <acz@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
> 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.
> This patch was originaly sent to linux-kernel@xxxxxxxxxxxxxxx.
> I am resending it to linux-acpi@xxxxxxxxxxxxxxx as per request of
> Rafael J. Wysocki to gather more visibility.
> Please let us know if you see possible issues with not erasing the flags or this
> modification seems acceptable.
I've applied the patch as 5.13 material, thanks!
> 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);
> --
> 2.17.1
>
