Re: [PATCH v6] ARM: vfp: Always save VFP state in vfp_pm_suspend on UP
On Mon, Jul 16, 2012 at 11:34 AM, Nicolas Pitre
wrote:
> On Mon, 16 Jul 2012, Colin Cross wrote:
>
>> vfp_pm_suspend should save the VFP state in suspend after
>> any lazy context switch. If it only saves when the VFP is enabled,
>> the state can get lost when, on a UP system:
>> Thread 1 uses the VFP
>> Context switch occurs to thread 2, VFP is disabled but the
>> VFP context is not saved
>> Thread 2 initiates suspend
>> vfp_pm_suspend is called with the VFP disabled, and the unsaved
>> VFP context of Thread 1 in the registers
>>
>> Modify vfp_pm_suspend to save the VFP context whenever
>> vfp_current_hw_state is not NULL.
>>
>> Includes a fix from Ido Yariv , who pointed out that on
>> SMP systems, the state pointer can be pointing to a freed task struct if
>> a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the
>> new if clause.
>>
>> Cc: Russell King
>> Cc: Barry Song
>> Cc: Catalin Marinas
>> Cc: Ido Yariv
>> Cc: Daniel Drake
>> Cc: Will Deacon
>> Signed-off-by: Colin Cross
>> ---
>> arch/arm/vfp/vfpmodule.c |6 ++
>> 1 files changed, 6 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
>> index 58696192..ce55f05 100644
>> --- a/arch/arm/vfp/vfpmodule.c
>> +++ b/arch/arm/vfp/vfpmodule.c
>> @@ -457,6 +457,12 @@ static int vfp_pm_suspend(void)
>>
>> /* disable, just in case */
>> fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
>> + } else if (vfp_current_hw_state[ti->cpu]) {
>> +#ifndef CONFIG_SMP
>> + fmxr(FPEXC, fpexc | FPEXC_EN);
>> + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);
>> + fmxr(FPEXC, fpexc);
>> +#endif
>> }
>
> Couldn't vfp_sync_hwstate() be used here instead?
Not easily, we don't have the thread struct of the thread that is in
the vfp hardware. We would have to read vfp_current_hw_state for the
current cpu and use container_of to get from struct vfpstate to
struct thread_info, and then pass that back in to vfp_sync_hwstate.
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Re: [PATCH v6] ARM: vfp: Always save VFP state in vfp_pm_suspend on UP
On Mon, 16 Jul 2012, Colin Cross wrote:
> vfp_pm_suspend should save the VFP state in suspend after
> any lazy context switch. If it only saves when the VFP is enabled,
> the state can get lost when, on a UP system:
> Thread 1 uses the VFP
> Context switch occurs to thread 2, VFP is disabled but the
> VFP context is not saved
> Thread 2 initiates suspend
> vfp_pm_suspend is called with the VFP disabled, and the unsaved
> VFP context of Thread 1 in the registers
>
> Modify vfp_pm_suspend to save the VFP context whenever
> vfp_current_hw_state is not NULL.
>
> Includes a fix from Ido Yariv , who pointed out that on
> SMP systems, the state pointer can be pointing to a freed task struct if
> a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the
> new if clause.
>
> Cc: Russell King
> Cc: Barry Song
> Cc: Catalin Marinas
> Cc: Ido Yariv
> Cc: Daniel Drake
> Cc: Will Deacon
> Signed-off-by: Colin Cross
> ---
> arch/arm/vfp/vfpmodule.c |6 ++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> index 58696192..ce55f05 100644
> --- a/arch/arm/vfp/vfpmodule.c
> +++ b/arch/arm/vfp/vfpmodule.c
> @@ -457,6 +457,12 @@ static int vfp_pm_suspend(void)
>
> /* disable, just in case */
> fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
> + } else if (vfp_current_hw_state[ti->cpu]) {
> +#ifndef CONFIG_SMP
> + fmxr(FPEXC, fpexc | FPEXC_EN);
> + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc);
> + fmxr(FPEXC, fpexc);
> +#endif
> }
Couldn't vfp_sync_hwstate() be used here instead?
Nicolas
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Re: [PATCH v6] ARM: vfp: Always save VFP state in vfp_pm_suspend on UP
On Mon, 16 Jul 2012, Colin Cross wrote:
vfp_pm_suspend should save the VFP state in suspend after
any lazy context switch. If it only saves when the VFP is enabled,
the state can get lost when, on a UP system:
Thread 1 uses the VFP
Context switch occurs to thread 2, VFP is disabled but the
VFP context is not saved
Thread 2 initiates suspend
vfp_pm_suspend is called with the VFP disabled, and the unsaved
VFP context of Thread 1 in the registers
Modify vfp_pm_suspend to save the VFP context whenever
vfp_current_hw_state is not NULL.
Includes a fix from Ido Yariv i...@wizery.com, who pointed out that on
SMP systems, the state pointer can be pointing to a freed task struct if
a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the
new if clause.
Cc: Russell King li...@arm.linux.org.uk
Cc: Barry Song b...@csr.com
Cc: Catalin Marinas catalin.mari...@arm.com
Cc: Ido Yariv i...@wizery.com
Cc: Daniel Drake d...@laptop.org
Cc: Will Deacon will.dea...@arm.com
Signed-off-by: Colin Cross ccr...@android.com
---
arch/arm/vfp/vfpmodule.c |6 ++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 58696192..ce55f05 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -457,6 +457,12 @@ static int vfp_pm_suspend(void)
/* disable, just in case */
fmxr(FPEXC, fmrx(FPEXC) ~FPEXC_EN);
+ } else if (vfp_current_hw_state[ti-cpu]) {
+#ifndef CONFIG_SMP
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(vfp_current_hw_state[ti-cpu], fpexc);
+ fmxr(FPEXC, fpexc);
+#endif
}
Couldn't vfp_sync_hwstate() be used here instead?
Nicolas
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Re: [PATCH v6] ARM: vfp: Always save VFP state in vfp_pm_suspend on UP
On Mon, Jul 16, 2012 at 11:34 AM, Nicolas Pitre
nicolas.pi...@linaro.org wrote:
On Mon, 16 Jul 2012, Colin Cross wrote:
vfp_pm_suspend should save the VFP state in suspend after
any lazy context switch. If it only saves when the VFP is enabled,
the state can get lost when, on a UP system:
Thread 1 uses the VFP
Context switch occurs to thread 2, VFP is disabled but the
VFP context is not saved
Thread 2 initiates suspend
vfp_pm_suspend is called with the VFP disabled, and the unsaved
VFP context of Thread 1 in the registers
Modify vfp_pm_suspend to save the VFP context whenever
vfp_current_hw_state is not NULL.
Includes a fix from Ido Yariv i...@wizery.com, who pointed out that on
SMP systems, the state pointer can be pointing to a freed task struct if
a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the
new if clause.
Cc: Russell King li...@arm.linux.org.uk
Cc: Barry Song b...@csr.com
Cc: Catalin Marinas catalin.mari...@arm.com
Cc: Ido Yariv i...@wizery.com
Cc: Daniel Drake d...@laptop.org
Cc: Will Deacon will.dea...@arm.com
Signed-off-by: Colin Cross ccr...@android.com
---
arch/arm/vfp/vfpmodule.c |6 ++
1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 58696192..ce55f05 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -457,6 +457,12 @@ static int vfp_pm_suspend(void)
/* disable, just in case */
fmxr(FPEXC, fmrx(FPEXC) ~FPEXC_EN);
+ } else if (vfp_current_hw_state[ti-cpu]) {
+#ifndef CONFIG_SMP
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(vfp_current_hw_state[ti-cpu], fpexc);
+ fmxr(FPEXC, fpexc);
+#endif
}
Couldn't vfp_sync_hwstate() be used here instead?
Not easily, we don't have the thread struct of the thread that is in
the vfp hardware. We would have to read vfp_current_hw_state for the
current cpu and use container_of to get from struct vfpstate to
struct thread_info, and then pass that back in to vfp_sync_hwstate.
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