Date:	Mon, 13 Apr 2015 16:54:16 +0200
From:	Jim Bos <jim876@...all.nl>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org, Lv Zheng <lv.zheng@...el.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bob Moore <robert.moore@...el.com>
Subject: Re: [PATCH] x86/ACPI: Fix regression caused by 16ee7b3dcc56 & c50f13c672df7

On 04/13/2015 03:36 PM, Rafael J. Wysocki wrote:
> On Monday, April 13, 2015 01:30:20 AM Rafael J. Wysocki wrote:
>> On Sunday, April 12, 2015 11:03:30 AM Jim Bos wrote:
>>> On 04/12/2015 03:29 AM, Rafael J. Wysocki wrote:
>>>> On Saturday, April 11, 2015 05:08:38 PM Jim Bos wrote:
>>>>> On 04/10/2015 03:56 AM, Jiang Liu wrote:
>>>>>> On 2015/4/10 0:41, Jim Bos wrote:
>>>>>>> On 04/09/2015 12:15 PM, Jiang Liu wrote:
>>>>>>>> On 2015/4/8 23:51, Jim Bos wrote:
>>>>>>>>> On 04/08/2015 07:26 AM, Jiang Liu wrote:
>>>>>>>>>> On 2015/4/8 0:49, Jim Bos wrote:
>>>>>>>>>>> On 04/07/2015 04:34 PM, Jiang Liu wrote:
>>>>>> <snip>
>>>>>>>> Hi Jim,
>>>>>>>> 	I'm really confused. I can't even explain why my previous
>>>>>>>> patch fixes the issue on AMD geode board now:(
>>>>>>>>
>>>>>>>> For the Dell laptop, seems you have:
>>>>>>>> 1) build a kernel with Local APIC and IOAPIC enabled
>>>>>>>> 2) lapic is disabled by BIOS, so there's no ACPI MADT(APIC)
>>>>>>>> table at all.
>>>>>>>> That means the laptop is working with 8259 PICs only.
>>>>>>>> There's little change between 3.16 and 4.0 related to 8259.
>>>>>>>>
>>>>>>>> For the AMD geode board, I still think original code is right.
>>>>>>>> I can't explain why the patch fix the issue.
>>>>>>>>
>>>>>>>> So could you please help to:
>>>>>>>> 1) Try to enable lapic on Dell laptop in BIOS
>>>>>>>> 2) Dump acpi tables and dmesg on AMD board
>>>>>>>>
>>>>>>>> If that still doesn't help, I will try to send you some
>>>>>>>> debug patches to gather more info.
>>>>>>>> Thanks!
>>>>>>>> Gerry
>>>>>>>>> _
>>>>>>>>> Jim
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> Gerry,
>>>>>>>
>>>>>>> As you mentioned your patch shouldn't make a difference, run some more
>>>>>>> tests, as it turns out:
>>>>>>> - geode system  broken on 3.16+ up to and including 3.19, however, on
>>>>>>> plain 4.0-rc6 it works!  Root cause appears to be there isn't an ACPI
>>>>>>> interrupt assigned in non-working kernels.
>>>>>>> - other system I got my hands on: Pentium(R) CPU G3220, broken on 3.19.0
>>>>>>> when boot parameter 'nosmp' is specified, again no acpi entry in
>>>>>>> /proc/interrupts,  working fine on 4.0-rc6
>>>>>>>
>>>>>>> So obviously between 3.19 and 4.0-rc6 something got fixed here!
>>>>>> Hi Jim,
>>>>>> Yes, the bugfix patch should be:
>>>>>> commit 1ea76fbadd66("x86/irq: Fix regression caused by commit b568b8601f05")
>>>>>>
>>>>>>> The Dell laptop remains the only problem then on 4.0-rc6, there IS an
>>>>>>> acpi interrupt  (but firing once apparently).
>>>>>>> There isn't an option in BIOS to enable LAPIC, however, when specifying
>>>>>>> 'lapic' as boot parameter I got interesting result, still not working
>>>>>>> and /proc/interrups still shows XT-PIC.  Doing a diff between dmesg on
>>>>>>> 3.19 and 4.0-rc6 this pops out:
>>>>>>>
>>>>>>> -Local APIC disabled by BIOS -- you can enable it with "lapic"
>>>>>>> -APIC: disable apic facility
>>>>>>> -APIC: switched to apic NOOP
>>>>>>> +Local APIC disabled by BIOS -- reenabling.
>>>>>>> +Found and enabled local APIC!
>>>>>>>
>>>>>>> +Enabling APIC mode:  Flat.  Using 0 I/O APICs
>>>>>> What's the last know working kernel for Dell laptop?
>>>>>> Does it work as expected with v3.19 kernel?
>>>>>> Do you means this message is from plain v4.0-rc6 kernel?
>>>>>> Thanks!
>>>>>> Gerry
>>>>>>
>>>>>>>
>>>>>>> Jim
>>>>>>>
>>>>>>
>>>>>
>>>>> Gerry, Rafael,
>>>>>
>>>>> Ok, found it.
>>>>> It was very 'interesting' bisect, because there were 2 overlapping
>>>>> issues here.  On the Dell laptop some kernels there wasn't an ACPI
>>>>> interrupt at all or it fired once and then seemed to get stuck.
>>>>> Turns out that kernel version:
>>>>> 3.16: OK
>>>>> 3.17: Broken (no acpi interrupt)
>>>>> 3.18: actually fine
>>>>> 3.19: Broken
>>>>>
>>>>> So started bisecting between 3.18 or 3.19, in the end found Rafael's
>>>>> patch which broke it:
>>>>>
>>>>> ==
>>>>> commit c50f13c672df758b59e026c15b9118f3ed46edc4
>>>>> Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>>> Date:   Mon Dec 1 23:50:16 2014 +0100
>>>>>
>>>>>     ACPICA: Save current masks of enabled GPEs after enable register writes
>>>>> ==
>>>>>
>>>>> Reverting that patch on top of 4.0-rc7 (with some offsets and one
>>>>> trivial manual edit) and I finally got a working ACPI interrupt again!
>>>>
>>>> That's unexpected.
>>>>
>>>> Is system suspend/resume involved in the reproduction of the problem in any way?
>>>>
>>>> In any case, does it help if you replace "enable_mask" with "enable_for_run"
>>>> in line 127 of drivers/acpi/acpica/hwgpe.c (without reverting the whole commit)?
>>>>
>>>>
>>>
>>> No suspends/resumes, but this suggestion works :-)
>>
>> OK
>>
>>> --- hwgpe.c.ORIG        2015-04-12 10:41:11.754104398 +0200
>>> +++ hwgpe.c     2015-04-12 10:42:38.021283593 +0200
>>> @@ -124,7 +124,7 @@
>>>
>>>                 /* Only enable if the corresponding enable_mask bit is
>>> set */
>>>
>>> -               if (!(register_bit & gpe_register_info->enable_mask)) {
>>> +               if (!(register_bit & gpe_register_info->enable_for_run)) {
>>>                         return (AE_BAD_PARAMETER);
>>>                 }
>>>
>>> Tested-by: Jim Bos <jim876@...all.nl>
>>
>> No, no, this is not a fix. :-)
>>
>> It means, though, that enable_for_run and enable_mask diverge at one point and,
>> moreover, enable_for_run has more bits set, which is *really* mysterious.
>>
>> So the only place modifying enable_for_run is acpi_ev_update_gpe_enable_mask()
>> which roughly does this:
>> 	(a) Find the register bit corresponding to the given GPE.
>> 	(b) Clear that bit in enable_for_run.
>> 	(c) If runtime_count is set for the GPE, set that bit in enable_for_run.
>> Thus the only case when a bit may be set in enable_for_run is when runtime_count
>> is nonzero for the GPE in acpi_ev_update_gpe_enable_mask().
>>
>> Now, acpi_ev_update_gpe_enable_mask() is only called from two places,
>> acpi_ev_add_gpe_reference() and acpi_ev_remove_gpe_reference().  The former
>> calls it when runtime_count has just been incremented and is now equal to one
>> and the latter calls it when runtime_count has just been decremented and is now
>> equal to zero.  Hence, if all of the involved functions return AE_OK,
>> acpi_ev_add_gpe_reference() may set the corresponding bit in enable_for_run
>> and acpi_ev_remove_gpe_reference() may clear it.
>>
>> Further, having set the bit in enable_for_run, acpi_ev_add_gpe_reference() calls
>> acpi_ev_enable_gpe() which then calls acpi_hw_low_set_gpe() with ACPI_GPE_SAVE_MASK
>> set in the second argument.  Again, this causes the corresponding bit to be set in
>> the register's enable_mask, unless any errors are returned.  In that case the
>> bit will be set in both enable_for_run and enable_mask and analogously for
>> acpi_ev_remove_gpe_reference().  So if I'm not overlooking anything and if all of
>> the involved calls are successful, enable_for_run and enable_mask will always be
>> in sync.
>>
>> As far as I can say that may change *only* if there's an error, because in that
>> case (1) we may not save the mask that we attempted to write to the register and
>> (2) we will reset runtime_count *without* updating enable_for_run which arguably
>> is a bug.  So the previous patch might just work accidentally.
>>
>> If that theory holds any water, the patch below may help too (instead of the
>> previous one), so please test it.  If it doesn't help, we'll need to find out
>> what exactly happens on that system, but surely it is *not* usual behavior.
> 
> Actually, the one below is better, so please test this one instead.
> 
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: ACPICA: Store GPE register enable masks upfront
> 
> It is reported that ACPI interrupts do not work any more on
> Dell Latitude D600 after commit c50f13c672df (ACPICA: Save
> current masks of enabled GPEs after enable register writes).
> The problem turns out to be related to the fact that the
> enable_mask and enable_for_run GPE bit masks are not in
> sync (in the absence of any system suspend/resume events)
> for at least one GPE register on that machine.
> 
> Address this problem by writing the enable_for_run mask into
> enable_mask as soon as enable_for_run is updated instead of
> doing that only after the subsequent register write has
> succeeded.  For consistency, update acpi_hw_gpe_enable_write()
> to store the bit mask to be written into the GPE register
> in enable_mask unconditionally before the write.
> 
> Since the ACPI_GPE_SAVE_MASK flag is not necessary any more after
> that, drop it along with the symbols depending on it.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/acpica/evgpe.c |    5 +++--
>  drivers/acpi/acpica/hwgpe.c |   11 ++++-------
>  include/acpi/actypes.h      |    4 ----
>  3 files changed, 7 insertions(+), 13 deletions(-)
> 
> Index: linux-pm/drivers/acpi/acpica/hwgpe.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpica/hwgpe.c
> +++ linux-pm/drivers/acpi/acpica/hwgpe.c
> @@ -89,6 +89,8 @@ u32 acpi_hw_get_gpe_register_bit(struct
>   * RETURN:	Status
>   *
>   * DESCRIPTION: Enable or disable a single GPE in the parent enable register.
> + *              The enable_mask field of the involved GPE register structure
> + *              must be updated by the caller if necessary.
>   *
>   ******************************************************************************/
>  
> @@ -119,7 +121,7 @@ acpi_hw_low_set_gpe(struct acpi_gpe_even
>  	/* Set or clear just the bit that corresponds to this GPE */
>  
>  	register_bit = acpi_hw_get_gpe_register_bit(gpe_event_info);
> -	switch (action & ~ACPI_GPE_SAVE_MASK) {
> +	switch (action) {
>  	case ACPI_GPE_CONDITIONAL_ENABLE:
>  
>  		/* Only enable if the corresponding enable_mask bit is set */
> @@ -149,9 +151,6 @@ acpi_hw_low_set_gpe(struct acpi_gpe_even
>  	/* Write the updated enable mask */
>  
>  	status = acpi_hw_write(enable_mask, &gpe_register_info->enable_address);
> -	if (ACPI_SUCCESS(status) && (action & ACPI_GPE_SAVE_MASK)) {
> -		gpe_register_info->enable_mask = (u8)enable_mask;
> -	}
>  	return (status);
>  }
>  
> @@ -286,10 +285,8 @@ acpi_hw_gpe_enable_write(u8 enable_mask,
>  {
>  	acpi_status status;
>  
> +	gpe_register_info->enable_mask = enable_mask;
>  	status = acpi_hw_write(enable_mask, &gpe_register_info->enable_address);
> -	if (ACPI_SUCCESS(status)) {
> -		gpe_register_info->enable_mask = enable_mask;
> -	}
>  	return (status);
>  }
>  
> Index: linux-pm/include/acpi/actypes.h
> ===================================================================
> --- linux-pm.orig/include/acpi/actypes.h
> +++ linux-pm/include/acpi/actypes.h
> @@ -736,10 +736,6 @@ typedef u32 acpi_event_status;
>  #define ACPI_GPE_ENABLE                 0
>  #define ACPI_GPE_DISABLE                1
>  #define ACPI_GPE_CONDITIONAL_ENABLE     2
> -#define ACPI_GPE_SAVE_MASK              4
> -
> -#define ACPI_GPE_ENABLE_SAVE            (ACPI_GPE_ENABLE | ACPI_GPE_SAVE_MASK)
> -#define ACPI_GPE_DISABLE_SAVE           (ACPI_GPE_DISABLE | ACPI_GPE_SAVE_MASK)
>  
>  /*
>   * GPE info flags - Per GPE
> Index: linux-pm/drivers/acpi/acpica/evgpe.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpica/evgpe.c
> +++ linux-pm/drivers/acpi/acpica/evgpe.c
> @@ -92,6 +92,7 @@ acpi_ev_update_gpe_enable_mask(struct ac
>  		ACPI_SET_BIT(gpe_register_info->enable_for_run,
>  			     (u8)register_bit);
>  	}
> +	gpe_register_info->enable_mask = gpe_register_info->enable_for_run;
>  
>  	return_ACPI_STATUS(AE_OK);
>  }
> @@ -123,7 +124,7 @@ acpi_status acpi_ev_enable_gpe(struct ac
>  
>  	/* Enable the requested GPE */
>  
> -	status = acpi_hw_low_set_gpe(gpe_event_info, ACPI_GPE_ENABLE_SAVE);
> +	status = acpi_hw_low_set_gpe(gpe_event_info, ACPI_GPE_ENABLE);
>  	return_ACPI_STATUS(status);
>  }
>  
> @@ -202,7 +203,7 @@ acpi_ev_remove_gpe_reference(struct acpi
>  		if (ACPI_SUCCESS(status)) {
>  			status =
>  			    acpi_hw_low_set_gpe(gpe_event_info,
> -						ACPI_GPE_DISABLE_SAVE);
> +						ACPI_GPE_DISABLE);
>  		}
>  
>  		if (ACPI_FAILURE(status)) {
> 
> --
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> 

Works!  If this is actually the fix ;-)

Tested-by: Jim Bos <jim876@...all.nl>


_
Jim


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