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SubjectRe: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform
On 2015/3/4 13:31, Ingo Molnar wrote:
>
> * 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.

So you are suggesting we extend a new x86 platform branch and override
the x86_platform and pm_power_off and reboot, like what intel_mid does?

Thanks,
-Aubrey

>
> Thanks,
>
> Ingo
> --
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