Re: ACPI: Processor native C-states using MWAIT

Re: ACPI: Processor native C-states using MWAIT

[Darrick J. Wong]

This patch breaks C-state discovery on my IBM IntelliStation Z30
because the return value of acpi_processor_get_power_info_fadt is not
assigned to "result" in the case that acpi_processor_get_power_info_cst
returns -ENODEV.  Thus, if ACPI provides C-state data via the FADT and
not _CST (as is the case on this machine), we incorrectly exit the
function with -ENODEV after reading the FADT.  The attached patch
sets the value of result so that we don't exit early.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

--

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 526387d..5c118cb 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -962,7 +962,7 @@ static int acpi_processor_get_power_info
 
 	result = acpi_processor_get_power_info_cst(pr);
 	if (result == -ENODEV)
-		acpi_processor_get_power_info_fadt(pr);
+		result = acpi_processor_get_power_info_fadt(pr);
 
 	if (result)
 		return result;

RE: ACPI: Processor native C-states using MWAIT

[Pallipadi, Venkatesh]

Acked

Andrew: Please apply this patch.

Thanks,
Venki 

>-----Original Message-----
>From: Darrick J. Wong [mailto:djwong@us.ibm.com] 
>Sent: Tuesday, October 17, 2006 4:19 PM
>To: Pallipadi, Venkatesh; Linux Kernel Mailing List
>Subject: Re: ACPI: Processor native C-states using MWAIT
>
>This patch breaks C-state discovery on my IBM IntelliStation Z30
>because the return value of acpi_processor_get_power_info_fadt is not
>assigned to "result" in the case that acpi_processor_get_power_info_cst
>returns -ENODEV.  Thus, if ACPI provides C-state data via the FADT and
>not _CST (as is the case on this machine), we incorrectly exit the
>function with -ENODEV after reading the FADT.  The attached patch
>sets the value of result so that we don't exit early.
>
>Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
>
>--
>
>diff --git a/drivers/acpi/processor_idle.c 
>b/drivers/acpi/processor_idle.c
>index 526387d..5c118cb 100644
>--- a/drivers/acpi/processor_idle.c
>+++ b/drivers/acpi/processor_idle.c
>@@ -962,7 +962,7 @@ static int acpi_processor_get_power_info
> 
> 	result = acpi_processor_get_power_info_cst(pr);
> 	if (result == -ENODEV)
>-		acpi_processor_get_power_info_fadt(pr);
>+		result = acpi_processor_get_power_info_fadt(pr);
> 
> 	if (result)
> 		return result;
>