Re: [PATCH] acpi: Fix access to PM1 control and status registers

[Anthony PERARD]

On Wed, Jul 01, 2020 at 08:01:55AM -0400, Michael S. Tsirkin wrote:
> On Wed, Jul 01, 2020 at 12:05:49PM +0100, Anthony PERARD wrote:
> > The ACPI spec state that "Accesses to PM1 control registers are
> > accessed through byte and word accesses." (In section 4.7.3.2.1 PM1
> > Control Registers of my old spec copy rev 4.0a).
> > 
> > With commit 5d971f9e6725 ("memory: Revert "memory: accept mismatching
> > sizes in memory_region_access_valid""), it wasn't possible anymore to
> > access the pm1_cnt register by reading a single byte, and that is use
> > by at least a Xen firmware called "hvmloader".
> > 
> > Also, take care of the PM1 Status Registers which also have "Accesses
> > to the PM1 status registers are done through byte or word accesses"
> > (In section 4.7.3.1.1 PM1 Status Registers).
> > 
> > Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> 
> 
> Can't we set impl.min_access_size to convert byte accesses
> to word accesses?

I actually tried, but when reading `addr` or `addr+1` I had the same
value. So I guess `addr` wasn't taken into account.

I've checked again, with `.impl.min_access_size = 2`, the width that the
function acpi_pm_cnt_read() get is 2, but addr isn't changed so the
function is still supposed to shift the result (or the value to write)
based on addr, I guess.

-- 
Anthony PERARD