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From: Ingo Molnar <mingo@kernel.org>
To: "Li, Aubrey" <aubrey.li@linux.intel.com>
Cc: "alan@linux.intel.com" <alan@linux.intel.com>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	arjan@linux.intel.com, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Len.Brown@intel.com, x86@kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform
Date: Wed, 4 Mar 2015 06:31:06 +0100	[thread overview]
Message-ID: <20150304053106.GA3701@gmail.com> (raw)
In-Reply-To: <54F69774.2050400@linux.intel.com>


* Li, Aubrey <aubrey.li@linux.intel.com> wrote:

> On 2015/3/4 13:08, Ingo Molnar wrote:
> > 
> > * Li, Aubrey <aubrey.li@linux.intel.com> wrote:
> > 
> >> On ACPI hardware reduced platform, the legacy PIC and PIT may not be
> >> initialized even though they may be present in silicon. Touching
> >> these legacy components causes unexpected result on system.
> >>
> >> On Bay Trail-T(ASUS-T100) platform, touching these legacy components
> >> blocks platform hardware low idle power state(S0ix) during system suspend.
> >> So we should bypass them on ACPI hardware reduced platform.
> >>
> >> Suggested-by: Arjan van de Ven <arjan@linux.intel.com>
> >> Signed-off-by: Li Aubrey <aubrey.li@linux.intel.com>
> >> Cc: Len Brown <len.brown@intel.com>
> >> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> ---
> >>  arch/x86/kernel/irqinit.c | 6 +++++-
> >>  arch/x86/kernel/time.c    | 3 ++-
> >>  2 files changed, 7 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
> >> index 70e181e..9a64cc3 100644
> >> --- a/arch/x86/kernel/irqinit.c
> >> +++ b/arch/x86/kernel/irqinit.c
> >> @@ -75,7 +75,11 @@ void __init init_ISA_irqs(void)
> >>  #if defined(CONFIG_X86_64) || defined(CONFIG_X86_LOCAL_APIC)
> >>  	init_bsp_APIC();
> >>  #endif
> >> -	legacy_pic->init(0);
> >> +	if (acpi_gbl_reduced_hardware) {
> >> +		pr_info("Using NULL legacy PIC\n");
> >> +		legacy_pic = &null_legacy_pic;
> >> +	} else
> >> +		legacy_pic->init(0);
> >>  
> >>  	for (i = 0; i < nr_legacy_irqs(); i++)
> >>  		irq_set_chip_and_handler(i, chip, handle_level_irq);
> >> diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
> >> index 25adc0e..5ba94fa 100644
> >> --- a/arch/x86/kernel/time.c
> >> +++ b/arch/x86/kernel/time.c
> >> @@ -14,6 +14,7 @@
> >>  #include <linux/i8253.h>
> >>  #include <linux/time.h>
> >>  #include <linux/export.h>
> >> +#include <linux/acpi.h>
> >>  
> >>  #include <asm/vsyscall.h>
> >>  #include <asm/x86_init.h>
> >> @@ -76,7 +77,7 @@ void __init setup_default_timer_irq(void)
> >>  /* Default timer init function */
> >>  void __init hpet_time_init(void)
> >>  {
> >> -	if (!hpet_enable())
> >> +	if (!hpet_enable() && !acpi_gbl_reduced_hardware)
> >>  		setup_pit_timer();
> >>  	setup_default_timer_irq();
> >>  }
> > 
> > So the whole acpi_gbl_reduced_hardware flaggery sucks as it mixes 
> > various hardware drivers that have little relation to each other...
> > 
> > Instead of having a proper platform init this flag hooks into various 
> > drivers and generic code, such as the efi reboot and shutdown code, 
> > and now the generic irq init code.
> > 
> > For this IRQ init problem, why not add a proper callback to 
> > x86_platform_ops, define your own IRQ init function, initialize it in 
> > your platform init sequence and let it be called? That solves it 
> > without creating an ugly mix of different platform methods.
> > 
> > For the EFI shutdown case, what's wrong with setting your own 
> > pm_power_off handler like most of the other platforms are doing? Plus 
> > the EFI code in drivers/firmware/efi/reboot.c should probably only set 
> > the shutdown handler if pm_power_off is still NULL.
> 
> I think our goal is to make the code as generic as possible for all 
> x86 platform, rather than creating a new x86 branch, I added Alan 
> Cox for this strategy discussion.
> 
> Do you have any inputs for the patch itself?

Other than that the patch is unacceptable for an upstream merge in its 
current form for the reason I mentioned? No.

Thanks,

	Ingo

  reply	other threads:[~2015-03-04  5:31 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-04  3:23 Li, Aubrey
2015-03-04  5:08 ` Ingo Molnar
2015-03-04  5:26   ` Li, Aubrey
2015-03-04  5:31     ` Ingo Molnar [this message]
2015-03-04  6:04       ` Li, Aubrey
2015-03-04  7:37         ` Ingo Molnar
2015-03-04  8:43           ` Arjan van de Ven
2015-03-04  9:50             ` Borislav Petkov
2015-03-04 14:16               ` Rafael J. Wysocki
2015-03-04 14:05                 ` Borislav Petkov
2015-03-04 14:38                   ` Rafael J. Wysocki
2015-03-04 20:21                   ` Alan Cox
2015-03-04 21:52                     ` Rafael J. Wysocki
2015-03-05 11:26                       ` Li, Aubrey
2015-03-05 16:05                       ` Alan Cox
2015-03-04 14:36               ` Arjan van de Ven
2015-03-04 20:11                 ` Ingo Molnar
2015-03-05 11:13                   ` Li, Aubrey
2015-03-05 11:36                     ` Ingo Molnar
2015-03-05 12:42                       ` Li, Aubrey
2015-03-05 16:06                         ` Alan Cox
2015-03-09 23:26                         ` Li, Aubrey
2015-03-10  8:06                           ` Ingo Molnar
2015-03-11  4:14                             ` Li, Aubrey
2015-03-04 20:18               ` Alan Cox

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