Message-ID: <20160627084911.GN13845@localhost.localdomain>
Date:	Mon, 27 Jun 2016 11:49:11 +0300
From:	Andrey Skvortsov <andrej.skvortzov@...il.com>
To:	"Zheng, Lv" <lv.zheng@...el.com>
Cc:	"Moore, Robert" <robert.moore@...el.com>,
	"Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"devel@...ica.org" <devel@...ica.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: acpi: broken suspend to RAM with v4.7-rc1

On 27 Jun, Zheng, Lv wrote:
> Hi,
> 
> > From: Andrey Skvortsov [mailto:andrej.skvortzov@...il.com]
> > Subject: Re: acpi: broken suspend to RAM with v4.7-rc1
> > 
> > On 24 Jun, Zheng, Lv wrote:
> > > Hi,
> > >
> > > > From: Andrey Skvortsov [mailto:andrej.skvortzov@...il.com]
> > > > Subject: Re: acpi: broken suspend to RAM with v4.7-rc1
> > > >
> > > > Hi Lv,
> > > >
> > > > On 13 Jun, Zheng, Lv wrote:
> > > > > > From: linux-acpi-owner@...r.kernel.org [mailto:linux-acpi-
> > > > > > owner@...r.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.acpid
> > > > ump.bin
> > > [Lv Zheng]
> > > I've been trying to download it these days but all failed.
> > > Could you send an off-list email to me with this attached?
> > Strange. I've check now. The link above is working, but I see that
> > part of the link above is moved to the next line.
> [Lv Zheng] 
> Maybe this is just because of ISP firewall.
> 
> > Anyway I resend you all files off-list.
> [Lv Zheng] 
> Great!
> 
> > 
> > 
> > > > > > > > > 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.
> > > [Lv Zheng]
> > > IMO, for the time being, you can use quirks.
> > > Booting your kernel with the following parameters:
> > >
> > > acpi=rsdt
> > > Or
> > > acpi_force_32bit_fadt_addr
> > > Or
> > > Both
> > 
> > Rafael reverted commit, so I'm ok now.
> > 
> > Actually acpi_force_32bit_fadt_addr will not help here, because it's take
> > effect only if address64 != address32. But here these addresses are
> > the same, therefore access_width is taken from extended address.
> > 
> > http://lxr.free-electrons.com/source/drivers/acpi/acpica/tbfadt.c#L576
> [Lv Zheng] 
> In addition to the address check, we may add access width check here.
> I need to check this with the decision makers.
Make sense. But then it's necessary to set default access width for registers from
FADT for this check. Because in the old 32-bit part of FADT only address and
length are defined, but not access width. 


> > acpi=rsdt helps. Thanks for the information about this option. I
> > missed it, when I read documentation.
> [Lv Zheng] 
> Great to know that at least 1 quirk works.
> Back to this bug, it seems we should use fixed access_width for some pre-defined PM registers.
This is what I meant by suggesting to reset xpm1a's
access_width to zero (or maybe another registers from FADT too) in
acpi_tb_setup_fadt_registers (see quoted diff above from my previous answer). 
If access_width is zero, then code works as before and access_width is 
calculated by acpi_hw_get_access_bit_width (will return reg->bit_width or
max_bit_width(32) in our case).

Setting access_width to some pre-defined value is an option.
But it's not as flexible, because ACPI specification doesn't define
access width and some pre-defined PM registers have variable length
and only the minimal register length is defined (PM1A Control Reg, PM1B Control
Reg, PM1A event block, PM1B event block).

Previously you pointed to commit that requires usage of access
width field.
http://permalink.gmane.org/gmane.linux.kernel.commits.head/313870
I see it's related to APEI, therefore setting access_width for
registers in FADT will not affect it.


-- 
Best regards,
Andrey Skvortsov

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