Re: ACPI "_PDC" - acpi_processor_set_pdc()- execution regression- Linux-3.x

[Wallak]

Hi Lin Ming,

This last patch, modifying the behavior of acpi_get_cpuid(), works fine 
on my non SMP enabled kernel. The test was done on a Dell X300, 
acpi_processor_set_pdc() was properly called, without the changes done 
by my previous patch.

Best Regards,
Wallak.

Lin Ming wrote:
> On Mon, 2011-12-12 at 10:26 +0800, Lin Ming wrote:
> > ---------- Forwarded message ----------
> > From:<wallak@xxxxxxx>
> > Date: Thu, Dec 8, 2011 at 6:38 AM
> > Subject: ACPI "_PDC" - acpi_processor_set_pdc()- execution regression
> > - Linux-3.x
> > To: linux-kernel@xxxxxxxxxxxxxxx
> >
> >
> > We have a regression on the ACPI stack of the last linux kernel line 3.x (3.1.4,
> > 3.2-rc4...). The ACPI "_PDC" chunk is not executed on some computers (e.g. Dell
> > X300; the function acpi_processor_set_pdc() is not called). This issue yield to
> > an uninitialized state of some ACPI variables.
> >
> > A patch is available below. This patch come back to the previous linux behavior,
> > and works fine.
> >
> > Best Regards,
> > Wallak.
> >
> > --- linux-3.1.4-mdf/drivers/acpi/processor_core.c.orig  2011-12-07
> > 23:12:57.000000000 +0100
> > +++ linux-3.1.4-mdf/drivers/acpi/processor_core.c       2011-12-07
> > 23:13:39.000000000 +0100
> > @@ -223,8 +223,8 @@
> >         type = (acpi_type == ACPI_TYPE_DEVICE) ? 1 : 0;
> >         cpuid = acpi_get_cpuid(handle, type, acpi_id);
> >
> > -       if (cpuid == -1)
> > -               return false;
> > +       if ((cpuid == -1)&&  (num_possible_cpus()>  1))
> Hi Wallak,
>
> BIOS may define multiple CPU handles even for UP
> processor(see below).
>
> processor_physically_present(acpi_handle handle) will be called for each
> CPU handles.
>
> We should only return valid value for CPU0 on UP processor.
> With your patch, processor_physically_present will return true for all
> CPU handles(CPU0, CPU1, CPU2, CPU3). This is not we want.
>
> I think below is the correct fix.
> Could you help to test it?
>
> Thanks.
>
> > From 5c6de7311ced7a1febf85fdcc08b6116bcfe8138 Mon Sep 17 00:00:00 2001
> From: Lin Ming<ming.m.lin@xxxxxxxxx>
> Date: Mon, 12 Dec 2011 10:04:53 +0800
> Subject: [PATCH] ACPI: processor: fix acpi_get_cpuid for UP processor
>
> For UP processor, it is likely that no _MAT method or MADT table defined.
> So currently acpi_get_cpuid(...) always return -1 for UP processor.
> This is wrong. It should return valid value for CPU0.
>
> In the other hand, BIOS may define multiple CPU handles even for UP
> processor, for example
>
>          Scope (_PR)
>          {
>              Processor (CPU0, 0x00, 0x00000410, 0x06) {}
>              Processor (CPU1, 0x01, 0x00000410, 0x06) {}
>              Processor (CPU2, 0x02, 0x00000410, 0x06) {}
>              Processor (CPU3, 0x03, 0x00000410, 0x06) {}
>          }
>
> We should only return valid value for CPU0's acpi handle.
> And return invalid value for others.
>
> http://marc.info/?t=132329819900003&r=1&w=2
>
> Reported-by: wallak@xxxxxxx
> Signed-off-by: Lin Ming<ming.m.lin@xxxxxxxxx>
> ---
>   drivers/acpi/processor_core.c |   26 ++++++++++++++++++++++++--
>   1 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
> index 3a0428e..3372900 100644
> --- a/drivers/acpi/processor_core.c
> +++ b/drivers/acpi/processor_core.c
> @@ -173,8 +173,30 @@ int acpi_get_cpuid(acpi_handle handle, int type, u32 acpi_id)
>   	apic_id = map_mat_entry(handle, type, acpi_id);
>   	if (apic_id == -1)
>   		apic_id = map_madt_entry(type, acpi_id);
> -	if (apic_id == -1)
> -		return apic_id;
> +	if (apic_id == -1) {
> +		/*
> +		 * On UP processor, there is no _MAT or MADT table.
> +		 * So above apic_id is always set to -1.
> +		 *
> +		 * BIOS may define multiple CPU handles even for UP processor.
> +		 * For example,
> +		 *
> +		 * Scope (_PR)
> +                 * {
> +		 *     Processor (CPU0, 0x00, 0x00000410, 0x06) {}
> +		 *     Processor (CPU1, 0x01, 0x00000410, 0x06) {}
> +		 *     Processor (CPU2, 0x02, 0x00000410, 0x06) {}
> +		 *     Processor (CPU3, 0x03, 0x00000410, 0x06) {}
> +		 * }
> +		 *
> +		 * Ignores apic_id and always return 0 for CPU0's handle.
> +		 * Return -1 for other CPU's handle.
> +		 */
> +		if (acpi_id == 0)
> +			return acpi_id;
> +		else
> +			return apic_id;
> +	}
>
>   #ifdef CONFIG_SMP
>   	for_each_possible_cpu(i) {

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