linux-kernel - [PATCH] resource: Prevent irqresource

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Date:   Mon, 29 Mar 2021 21:52:38 +0200
From:   Angela Czubak <acz@...ihalf.com>
To:     rafael.j.wysocki@...el.com
Cc:     akpm@...ux-foundation.org, john.garry@...wei.com,
        linux-kernel@...r.kernel.org, upstream@...ihalf.com,
        dtor@...omium.org, Angela Czubak <acz@...ihalf.com>
Subject: [PATCH] resource: Prevent irqresource_disabled() from erasing flags

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@...ihalf.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.
Best Regards,
Angela

 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