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

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Message-ID: <20160611104922.GA2368@nest>
Date:	Sat, 11 Jun 2016 13:49:22 +0300
From:	Andrey Skvortsov <andrej.skvortzov@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Lv Zheng <lv.zheng@...el.com>, Bob Moore <robert.moore@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	linux-acpi@...r.kernel.org, devel@...ica.org,
	linux-kernel@...r.kernel.org
Subject: Re: acpi: broken suspend to RAM with v4.7-rc1

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_h=
> > w_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 B=
> > lock
> > (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-b=
> > it), but it's=20
> > 1 (8-bit).
> > 
> > The root of the problem seems to be not the commit 66b1ed5aa8dd25 itself, b=
> > ut 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?
> 
> 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.

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;


-- 
Best regards,
Andrey Skvortsov



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