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Re: [Xen-devel] [PATCH v4 3/5] acpi: Adjust linux acpi OS functions to new extended parameter

On 06/27/2013 04:19 PM, Moore, Robert wrote:
I'm the ACPICA owner.

Apologies, I should have looked that up when Rafael asked for you to be CC'ed

The issue I have is that acpi_os_prepare_sleep causes a divergence between the raw ACPICA 
source code and the "linux" version of the ACPICA code.

Understood. The v2 version of this patchset was discussed with Jan Beulich here:


In this thread, Rafael suggests that these changes be made, and submitted through linux-acpi, with he, and you CC'ed.

This is more of a cleanup effort to existing functionality, that did not get coordinated. That is, as the comment indicates, in linux 3.4, reduced hardware sleep was introduced as part of ACPIv5. In parallel, acpi_os_prepare_sleep() was also introduced, to allow for subsystems such as Xen, and tboot to take advantage of the vast majority of ACPICA, but hook some low level capabilities via function pointer, to do the specific things for those subsystems.

Rafael rightly pointed out that inclusion of linux/acpi.h in ACPICA code is wrong, and we should make efforts to avoid doing so. This patch is to clean this up, and also to extend the functionality to also go down the same path for the reduced hardware sleep path, passing that "extended" flag down to that subsystem, so that it might make use of it at the very low levels.

All efforts are being made to reduce the amount of churn in ACPICA, since it is an upstream project to linux.

If it is possible to implement the functionality that is needed without changes 
to ACPICA, then that would be best. If not, we are willing to integrate this 
interface into ACPICA. However, this has an impact on all operating systems 
that use ACPICA, so this is always the last resort.

I am unaware of a way to take advantage of the infrastructure that ACPICA provides, and also do that which is necessary to make it work in Xen / tboot without these hooks.

It would be greatly appreciated if you would consider this new interface for inclusion.

Thanks for your time.



-----Original Message-----
From: Ben Guthro [mailto:Benjamin.Guthro@xxxxxxxxxx]
Sent: Thursday, June 27, 2013 9:13 AM
To: Moore, Robert
Cc: Jan Beulich; Zheng, Lv; Box, David E; Brown, Len; xen-
devel@xxxxxxxxxxxxx; Konrad Rzeszutek Wilk; Rafaell J . Wysocki; linux-
acpi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v4 3/5] acpi: Adjust linux acpi OS functions to new
extended parameter

On 06/27/2013 11:59 AM, Moore, Robert wrote:
I have not seen a discussion of the details on this, so can someone
explain to me just why acpi_os_prepare_sleep is needed, what does it do,
and why these changes are being made to ACPICA code?

Hi Bob,

I'm not familiar with your background here, so I apologize if I am stating
obvious things below.

acpi_os_prepare_sleep() has been in the acpica code for some time now,
allowing for OS specific hooks to account for differences between OS

Specifically, it has been in since:

commit 09f98a825a821f7a3f1b162f9ed023f37213a63b
Author: Tang Liang <liang.tang@xxxxxxxxxx>
Date:   Fri Dec 9 10:05:54 2011 +0800

     x86, acpi, tboot: Have a ACPI os prepare sleep instead of calling

     The ACPI suspend path makes a call to tboot_sleep right before
     it writes the PM1A, PM1B values. We replace the direct call to
     tboot via an registration callback similar to __acpi_register_gsi.

     CC: Len Brown <len.brown@xxxxxxxxx>
     Acked-by: Joseph Cihula <joseph.cihula@xxxxxxxxx>
     Acked-by: Rafael J. Wysocki <rjw@xxxxxxx>
     [v1: Added __attribute__ ((unused))]
     [v2: Introduced a wrapper instead of changing tboot_sleep return
     [v3: Added return value AE_CTRL_SKIP for acpi_os_sleep_prepare]
     Signed-off-by: Tang Liang <liang.tang@xxxxxxxxxx>
     [v1: Fix compile issues on IA64 and PPC64]
     [v2: Fix where __acpi_os_prepare_sleep==NULL and did not go in sleep
     Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

In this case, the Xen hypervisor, and not linux needs to actually put the
system into S3, so this hook gives the architecture to do so.

This change does not introduce this functionality, but simply moves the
code around into the proper locations, such that the acpica code no longer
need to include linux specific headers.

I hope this helps.
If you have specific questions, please let me know.



-----Original Message-----
From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
Sent: Thursday, June 27, 2013 8:12 AM
To: Ben Guthro
Cc: Moore, Robert; xen-devel@xxxxxxxxxxxxx; Konrad Rzeszutek Wilk;
Rafaell J . Wysocki; linux-acpi@xxxxxxxxxxxxxxx;
Subject: Re: [PATCH v4 3/5] acpi: Adjust linux acpi OS functions to
new extended parameter

On 27.06.13 at 17:02, Ben Guthro <benjamin.guthro@xxxxxxxxxx> wrote:
Change the function definitions of acpi_os_prepare_sleep() and
acpi_os_set_prepare_sleep() to pass along the new extended sleep

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Ben Guthro <benjamin.guthro@xxxxxxxxxx>
Cc: Bob Moore <robert.moore@xxxxxxxxx>
Cc: Rafaell J. Wysocki <rjw@xxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx
   drivers/acpi/osl.c   |   16 ++++++++--------
   include/linux/acpi.h |    6 +++---
   2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index
e721863..0251c9b 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -77,8 +77,8 @@ EXPORT_SYMBOL(acpi_in_debugger);  extern char
   #endif                               /*ENABLE_DEBUGGER */

-static int (*__acpi_os_prepare_sleep)(u8 sleep_state, u32 pm1a_ctrl,
-                                     u32 pm1b_ctrl);
+static int (*__acpi_os_prepare_sleep)(u8 sleep_state, u32 val_a,
+                                     bool extended);

So from here till patch 5 the build will be half broken because of
the type mismatches? I think at least the types of the consumers need
to be changed in this patch; leaving the meat of the Xen change to
patch 4 is perhaps fine.


   static acpi_osd_handler acpi_irq_handler;  static void
*acpi_irq_context; @@ -1757,13 +1757,13 @@ acpi_status
        return AE_OK;

-acpi_status acpi_os_prepare_sleep(u8 sleep_state, u32 pm1a_control,
-                                 u32 pm1b_control)
+acpi_status acpi_os_prepare_sleep(u8 sleep_state, u32 val_a, u32
+                                 u8 extended)
        int rc = 0;
        if (__acpi_os_prepare_sleep)
-               rc = __acpi_os_prepare_sleep(sleep_state,
-                                            pm1a_control, pm1b_control);
+               rc = __acpi_os_prepare_sleep(sleep_state, val_a, val_b,
+                                            extended);
        if (rc < 0)
                return AE_ERROR;
        else if (rc > 0)
@@ -1772,8 +1772,8 @@ acpi_status acpi_os_prepare_sleep(u8
sleep_state, u32 pm1a_control,
        return AE_OK;

-void acpi_os_set_prepare_sleep(int (*func)(u8 sleep_state,
-                              u32 pm1a_ctrl, u32 pm1b_ctrl))
+void acpi_os_set_prepare_sleep(int (*func)(u8 sleep_state, u32 val_a,
+                              u32 val_b, bool extended))
        __acpi_os_prepare_sleep = func;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h index
709a2f2..26f9996 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -477,8 +477,8 @@ static inline bool
acpi_driver_match_device(struct device *dev,
   #endif       /* !CONFIG_ACPI */

   #ifdef CONFIG_ACPI
-void acpi_os_set_prepare_sleep(int (*func)(u8 sleep_state,
-                              u32 pm1a_ctrl,  u32 pm1b_ctrl));
+void acpi_os_set_prepare_sleep(int (*func)(u8 sleep_state, u32 val_a,
+                              u32 val_b, bool extended));
   #ifdef CONFIG_X86
   void arch_reserve_mem_area(acpi_physical_address addr, size_t
size); #else @@ -488,7 +488,7 @@ static inline void
arch_reserve_mem_area(acpi_physical_address addr,  }  #endif /*
CONFIG_X86 */  #else -#define acpi_os_set_prepare_sleep(func,
pm1a_ctrl, pm1b_ctrl) do { } while
+#define acpi_os_set_prepare_sleep(func, val_a, val_b, ext) do { }
+while (0)

   #if defined(CONFIG_ACPI) && defined(CONFIG_PM_RUNTIME)

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