wdat_wdt: access width inconsistency

[Jean Delvare <jdelvare@suse.de>]

Hi all,

I'm still working on my customer issue where the wdat_wdt driver
reboots the server instantly as soon as the watchdog daemon is started.
I looked at all the upstream fixes and we already have all relevant
ones in our kernel so I start suspecting either a driver bug or a BIOS
issue.

While reading the driver code I noticed one suspect thing related to
the register access width, which I'd like a second opinion on.

Both acpi_watchdog.c and wdat_wdt.c contain code like:

	res.end = res.start + gas->access_width - 1;

This suggests that gas->access_width is expected to be 4 in case of a
32-bit register. However in wdat_wdt_read/wdat_wdt_write we have:

	switch (gas->access_width) {
	(...)
	case 3:
		*value = ioread32(instr->reg);

This looks inconsistent to me.

My reading of the ACPI specification suggests that 3 is the right value
for 32-bit registers. If so, then shouldn't the resource's end be set
to:

	res.end = res.start + (1 << (gas->access_width - 1)) - 1;

?

Thanks,
-- 
Jean Delvare
SUSE L3 Support