Re: acpi: broken suspend to RAM with v4.7-rc1

["Rafael J. Wysocki" <rafael@kernel.org>]

On Mon, Jun 13, 2016 at 12:07 PM, Andrey Skvortsov
<andrej.skvortzov@gmail.com> wrote:
> Hi Lv,
>
> On 13 Jun, Zheng, Lv wrote:
>> > From: linux-acpi-owner@vger.kernel.org [mailto:linux-acpi-
>> > owner@vger.kernel.org] On Behalf Of Rafael J. Wysocki
>> > Subject: Re: acpi: broken suspend to RAM with v4.7-rc1
>> >
>> > On Saturday, June 11, 2016 01:49:22 PM Andrey Skvortsov wrote:
>> > > On 10 Jun, Rafael J. Wysocki wrote:
>> > > > On Friday, June 10, 2016 11:32:10 PM Andrey Skvortsov wrote:
>> > > > > Hi,
>> > > > >
>> > > > > On my laptop (DELL Vostro 1500) in v4.7-rc1 is broken suspend to RAM.
>> > > > > Laptop doesn't finish suspend to RAM process (disks are off, but
>> > > > > WiFi and Power LEDs are still on). The only way to get it out of
>> > > > > this state, is to turn the power off.
>> > > > >
>> > > > > I've bisected the issue to commit 66b1ed5aa8dd25
>> > > > > [ACPICA: ACPI 2.0, Hardware: Add access_width/bit_offset support
>> > > > > for acpi_hw_write()].
>> > > > >
>> > > > > If I revert this commit in v4.7-rc1 (or v4.7-rc2), suspend to RAM
>> > > > > is working again.
>> > > > >
>> > > > > The cause of this problem is that after this commit write to PM1A
>> > > > > Control Block (16-bit register) is done using two 8-bit writes.
>> > > > > If I force this write to be 16-bit, then all is working as before.
>> > > > >
>> > > > > To get it working 'access_width' for PM1A Control Block needs to
>> > > > > be 2 (16-bit), but it's 1 (8-bit).
>> [Lv Zheng]
>> Could you send me the acpidump of the machine?
> Here it is
> https://dl.dropboxusercontent.com/u/24023626/dell_vostro_1500.acpidump.bin
>
>> > > > >
>> > > > > The root of the problem seems to be not the commit
>> > 66b1ed5aa8dd25
>> > > > > itself, but the ACPI tables in BIOS where wrong access_width
>> > > > > comes from. I fixed problem in FACP  table, put it in initrd to
>> > > > > override FACP table from BIOS. This fixed the issue, suspend to
>> > > > > RAM is working now again.
>> > > > >
>> > > > > But I'm not sure whether is this proper fix for this problem.
>> > > > > Is there any place in the kernel, where such ACPI quirks are placed?
>> [Lv Zheng]
>> My question would be:
>> Does Windows behave correctly for this table?
> Yes, suspend to RAM is working under Windows Vista.
> IIRC it worked under Windows XP too.
>
>> However there is a real case showing that there are real tables need us to correctly support BitWidth/BitOffset.
>> Here is the information for you to refer:
>> http://permalink.gmane.org/gmane.linux.kernel.commits.head/313870
>>
>> > > >
>> > > > Well, if the commit in question caused a problem to happen for you,
>> > > > it also might cause similar problems to happen elsewhere.
>> > > >
>> > > > It looks like we'll need to revert that commit.
>> > > Hi,
>> > >
>> > > or maybe to reset access_width AnyAcc from FACP table only for PM1A
>> > > control register or even for all registers? This will fix the issue too.
>> >
>> > That's a good idea actually.
>> >
>> > > diff --git a/drivers/acpi/acpica/tbfadt.c
>> > > b/drivers/acpi/acpica/tbfadt.c index 6208069..a476e94 100644
>> > > --- a/drivers/acpi/acpica/tbfadt.c
>> > > +++ b/drivers/acpi/acpica/tbfadt.c
>> > > @@ -714,7 +714,14 @@ static void acpi_tb_setup_fadt_registers(void)
>> > >                         }
>> > >                 }
>> > >         }
>> > >
>> > > +       /*
>> > > +        * Reset access_width in the GAS for PM1A control register to
>> > > +        * undefined value. Because in some cases this field contains
>> > > +        * wrong value.
>> > > +        */
>> > > +       acpi_gbl_FADT.xpm1a_control_block.access_width = 0;
>> >
>> > OK, let's see what Bob and Lv think about that.
>> [Lv Zheng]
>> There is a commit in 4.7-rc2:
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7f9bef9d
>> Have you tried if the problem still exists in 4.7-rc2?
> I've just tried v4.7-rc3. It contains commit 7f9bef9d and the problem
> exists there too.

I have decided to revert commit 66b1ed5aa8dd25 as in principle other
registers may be similarly affected on other systems.

Thanks,
Rafael