vfp_pm_suspend should save the VFP state any time there is
a last_VFP_context. 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 to allow lazy save and restore
Thread 2 initiates suspend
vfp_pm_suspend is called with the VFP disabled, but the
context has not been saved.
Modify vfp_pm_suspend to save the VFP context whenever
last_VFP_context is set.
Cc: Catalin Marinas <[email protected]>
Signed-off-by: Colin Cross <[email protected]>
---
arch/arm/vfp/vfpmodule.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 66bf8d1..7aea616 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -415,13 +415,12 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
struct thread_info *ti = current_thread_info();
u32 fpexc = fmrx(FPEXC);
- /* if vfp is on, then save state for resumption */
- if (fpexc & FPEXC_EN) {
+ /* save state for resume */
+ if (last_VFP_context[ti->cpu]) {
printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
- vfp_save_state(&ti->vfpstate, fpexc);
-
- /* disable, just in case */
- fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(last_VFP_context[ti->cpu], fpexc);
+ fmxr(FPEXC, fpexc & ~FPEXC_EN);
}
/* clear any information we had about last context state */
--
1.7.3.1
On Sun, 2011-02-13 at 23:13 +0000, Colin Cross wrote:
> vfp_pm_suspend should save the VFP state any time there is
> a last_VFP_context. 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 to allow lazy save and restore
> Thread 2 initiates suspend
> vfp_pm_suspend is called with the VFP disabled, but the
> context has not been saved.
At this point is it guaranteed that the thread won't migrate to another
CPU? If not, we should use get/put_cpu.
> --- a/arch/arm/vfp/vfpmodule.c
> +++ b/arch/arm/vfp/vfpmodule.c
> @@ -415,13 +415,12 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
> struct thread_info *ti = current_thread_info();
> u32 fpexc = fmrx(FPEXC);
>
> - /* if vfp is on, then save state for resumption */
> - if (fpexc & FPEXC_EN) {
> + /* save state for resume */
> + if (last_VFP_context[ti->cpu]) {
> printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
> - vfp_save_state(&ti->vfpstate, fpexc);
> -
> - /* disable, just in case */
> - fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
> + fmxr(FPEXC, fpexc | FPEXC_EN);
> + vfp_save_state(last_VFP_context[ti->cpu], fpexc);
> + fmxr(FPEXC, fpexc & ~FPEXC_EN);
> }
We may want to set the last_VFP_context to NULL so that after resuming
(to the same thread) we force the VFP reload from the vfpstate
structure. The vfp_support_entry code ignores the reloading if the
last_VFP_context is the same as vfpstate.
--
Catalin
On Mon, Feb 14, 2011 at 3:42 AM, Catalin Marinas
<[email protected]> wrote:
> On Sun, 2011-02-13 at 23:13 +0000, Colin Cross wrote:
>> vfp_pm_suspend should save the VFP state any time there is
>> a last_VFP_context. ?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 to allow lazy save and restore
>> ? ?Thread 2 initiates suspend
>> ? ?vfp_pm_suspend is called with the VFP disabled, but the
>> ? ? ? context has not been saved.
>
> At this point is it guaranteed that the thread won't migrate to another
> CPU? If not, we should use get/put_cpu.
Yes, VFP suspend is implemented with a sysdev, which is suspended
after disable_nonboot_cpus.
>> --- a/arch/arm/vfp/vfpmodule.c
>> +++ b/arch/arm/vfp/vfpmodule.c
>> @@ -415,13 +415,12 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
>> ? ? ? ? struct thread_info *ti = current_thread_info();
>> ? ? ? ? u32 fpexc = fmrx(FPEXC);
>>
>> - ? ? ? /* if vfp is on, then save state for resumption */
>> - ? ? ? if (fpexc & FPEXC_EN) {
>> + ? ? ? /* save state for resume */
>> + ? ? ? if (last_VFP_context[ti->cpu]) {
>> ? ? ? ? ? ? ? ? printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
>> - ? ? ? ? ? ? ? vfp_save_state(&ti->vfpstate, fpexc);
>> -
>> - ? ? ? ? ? ? ? /* disable, just in case */
>> - ? ? ? ? ? ? ? fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
>> + ? ? ? ? ? ? ? fmxr(FPEXC, fpexc | FPEXC_EN);
>> + ? ? ? ? ? ? ? vfp_save_state(last_VFP_context[ti->cpu], fpexc);
>> + ? ? ? ? ? ? ? fmxr(FPEXC, fpexc & ~FPEXC_EN);
>> ? ? ? ? }
>
> We may want to set the last_VFP_context to NULL so that after resuming
> (to the same thread) we force the VFP reload from the vfpstate
> structure. The vfp_support_entry code ignores the reloading if the
> last_VFP_context is the same as vfpstate.
Right, will fix.
vfp_pm_suspend should save the VFP state any time there is
a last_VFP_context. 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 to allow lazy save and restore
Thread 2 initiates suspend
vfp_pm_suspend is called with the VFP disabled, but the
context has not been saved.
Modify vfp_pm_suspend to save the VFP context whenever
last_VFP_context is set.
Cc: Catalin Marinas <[email protected]>
Signed-off-by: Colin Cross <[email protected]>
---
arch/arm/vfp/vfpmodule.c | 12 ++++++------
1 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 66bf8d1..7231d18 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
struct thread_info *ti = current_thread_info();
u32 fpexc = fmrx(FPEXC);
- /* if vfp is on, then save state for resumption */
- if (fpexc & FPEXC_EN) {
+ /* save state for resume */
+ if (last_VFP_context[ti->cpu]) {
printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
- vfp_save_state(&ti->vfpstate, fpexc);
-
- /* disable, just in case */
- fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(last_VFP_context[ti->cpu], fpexc);
+ last_VFP_context[ti->cpu] = NULL;
+ fmxr(FPEXC, fpexc & ~FPEXC_EN);
}
/* clear any information we had about last context state */
--
1.7.3.1
On Mon, 2011-02-14 at 22:55 +0000, Colin Cross wrote:
> vfp_pm_suspend should save the VFP state any time there is
> a last_VFP_context. 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 to allow lazy save and restore
> Thread 2 initiates suspend
> vfp_pm_suspend is called with the VFP disabled, but the
> context has not been saved.
>
> Modify vfp_pm_suspend to save the VFP context whenever
> last_VFP_context is set.
>
> Cc: Catalin Marinas <[email protected]>
> Signed-off-by: Colin Cross <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
On Mon, Feb 14, 2011 at 02:55:47PM -0800, Colin Cross wrote:
> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> index 66bf8d1..7231d18 100644
> --- a/arch/arm/vfp/vfpmodule.c
> +++ b/arch/arm/vfp/vfpmodule.c
> @@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
> struct thread_info *ti = current_thread_info();
> u32 fpexc = fmrx(FPEXC);
>
> - /* if vfp is on, then save state for resumption */
> - if (fpexc & FPEXC_EN) {
> + /* save state for resume */
> + if (last_VFP_context[ti->cpu]) {
I'm not entirely happy with this.
It is true that last_VFP_context[] when non-NULL indicates who owns the
hardware VFP state, so saving it would seem logical. However, this new
code now saves the state with the saved fpexc indicating that it's disabled.
This will cause a VFP exception to misbehave by reloading the state, and
then disabling the VFP unit. That will cause another VFP exception which
will find the VFP unit disabled, and re-enable it. All in all, this is
rather wasteful.
So...
/* If lazy disable, re-enable the VFP ready for it to be saved */
if (last_VFP_context[ti->cpu] != &ti->vfpstate) {
fpexc |= FPEXC_EN;
fmxr(FPEXC, fpexc);
}
/* If VFP is on, then save state for resumption */
if (fpexc & FPEXC_EN) {
...
On Tue, Feb 15, 2011 at 9:03 AM, Russell King - ARM Linux
<[email protected]> wrote:
> On Mon, Feb 14, 2011 at 02:55:47PM -0800, Colin Cross wrote:
>> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
>> index 66bf8d1..7231d18 100644
>> --- a/arch/arm/vfp/vfpmodule.c
>> +++ b/arch/arm/vfp/vfpmodule.c
>> @@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
>> ? ? ? struct thread_info *ti = current_thread_info();
>> ? ? ? u32 fpexc = fmrx(FPEXC);
>>
>> - ? ? /* if vfp is on, then save state for resumption */
>> - ? ? if (fpexc & FPEXC_EN) {
>> + ? ? /* save state for resume */
>> + ? ? if (last_VFP_context[ti->cpu]) {
>
> I'm not entirely happy with this.
>
> It is true that last_VFP_context[] when non-NULL indicates who owns the
> hardware VFP state, so saving it would seem logical. ?However, this new
> code now saves the state with the saved fpexc indicating that it's disabled.
>
> This will cause a VFP exception to misbehave by reloading the state, and
> then disabling the VFP unit. ?That will cause another VFP exception which
> will find the VFP unit disabled, and re-enable it. ?All in all, this is
> rather wasteful.
>
> So...
> ? ? ? ?/* If lazy disable, re-enable the VFP ready for it to be saved */
> ? ? ? ?if (last_VFP_context[ti->cpu] != &ti->vfpstate) {
> ? ? ? ? ? ? ? ?fpexc |= FPEXC_EN;
> ? ? ? ? ? ? ? ?fmxr(FPEXC, fpexc);
> ? ? ? ?}
> ? ? ? ?/* If VFP is on, then save state for resumption */
> ? ? ? ?if (fpexc & FPEXC_EN) {
> ? ? ? ? ? ? ? ?...
I think v2 of the patch handles this case correctly:
/* save state for resume */
if (last_VFP_context[ti->cpu]) {
printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
fmxr(FPEXC, fpexc | FPEXC_EN);
vfp_save_state(last_VFP_context[ti->cpu], fpexc);
last_VFP_context[ti->cpu] = NULL;
fmxr(FPEXC, fpexc & ~FPEXC_EN);
}
This version enables the VFP if it was not enabled, but saves the
original fpexc value.
On Wed, Feb 16, 2011 at 11:36:45AM -0800, Colin Cross wrote:
> On Tue, Feb 15, 2011 at 9:03 AM, Russell King - ARM Linux
> <[email protected]> wrote:
> > On Mon, Feb 14, 2011 at 02:55:47PM -0800, Colin Cross wrote:
> >> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
> >> index 66bf8d1..7231d18 100644
> >> --- a/arch/arm/vfp/vfpmodule.c
> >> +++ b/arch/arm/vfp/vfpmodule.c
> >> @@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
> >> ? ? ? struct thread_info *ti = current_thread_info();
> >> ? ? ? u32 fpexc = fmrx(FPEXC);
> >>
> >> - ? ? /* if vfp is on, then save state for resumption */
> >> - ? ? if (fpexc & FPEXC_EN) {
> >> + ? ? /* save state for resume */
> >> + ? ? if (last_VFP_context[ti->cpu]) {
> >
> > I'm not entirely happy with this.
> >
> > It is true that last_VFP_context[] when non-NULL indicates who owns the
> > hardware VFP state, so saving it would seem logical. ?However, this new
> > code now saves the state with the saved fpexc indicating that it's disabled.
> >
> > This will cause a VFP exception to misbehave by reloading the state, and
> > then disabling the VFP unit. ?That will cause another VFP exception which
> > will find the VFP unit disabled, and re-enable it. ?All in all, this is
> > rather wasteful.
> >
> > So...
> > ? ? ? ?/* If lazy disable, re-enable the VFP ready for it to be saved */
> > ? ? ? ?if (last_VFP_context[ti->cpu] != &ti->vfpstate) {
> > ? ? ? ? ? ? ? ?fpexc |= FPEXC_EN;
> > ? ? ? ? ? ? ? ?fmxr(FPEXC, fpexc);
> > ? ? ? ?}
> > ? ? ? ?/* If VFP is on, then save state for resumption */
> > ? ? ? ?if (fpexc & FPEXC_EN) {
> > ? ? ? ? ? ? ? ?...
>
> I think v2 of the patch handles this case correctly:
> /* save state for resume */
> if (last_VFP_context[ti->cpu]) {
> printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
> fmxr(FPEXC, fpexc | FPEXC_EN);
> vfp_save_state(last_VFP_context[ti->cpu], fpexc);
This saves fpexc with the enable flag possibly clear.
> last_VFP_context[ti->cpu] = NULL;
> fmxr(FPEXC, fpexc & ~FPEXC_EN);
> }
>
> This version enables the VFP if it was not enabled, but saves the
> original fpexc value.
Which is wrong as I said above.
On Sun, Feb 20, 2011 at 4:57 AM, Russell King - ARM Linux
<[email protected]> wrote:
> On Wed, Feb 16, 2011 at 11:36:45AM -0800, Colin Cross wrote:
>> On Tue, Feb 15, 2011 at 9:03 AM, Russell King - ARM Linux
>> <[email protected]> wrote:
>> > On Mon, Feb 14, 2011 at 02:55:47PM -0800, Colin Cross wrote:
>> >> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
>> >> index 66bf8d1..7231d18 100644
>> >> --- a/arch/arm/vfp/vfpmodule.c
>> >> +++ b/arch/arm/vfp/vfpmodule.c
>> >> @@ -415,13 +415,13 @@ static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
>> >> ? ? ? struct thread_info *ti = current_thread_info();
>> >> ? ? ? u32 fpexc = fmrx(FPEXC);
>> >>
>> >> - ? ? /* if vfp is on, then save state for resumption */
>> >> - ? ? if (fpexc & FPEXC_EN) {
>> >> + ? ? /* save state for resume */
>> >> + ? ? if (last_VFP_context[ti->cpu]) {
>> >
>> > I'm not entirely happy with this.
>> >
>> > It is true that last_VFP_context[] when non-NULL indicates who owns the
>> > hardware VFP state, so saving it would seem logical. ?However, this new
>> > code now saves the state with the saved fpexc indicating that it's disabled.
>> >
>> > This will cause a VFP exception to misbehave by reloading the state, and
>> > then disabling the VFP unit. ?That will cause another VFP exception which
>> > will find the VFP unit disabled, and re-enable it. ?All in all, this is
>> > rather wasteful.
>> >
>> > So...
>> > ? ? ? ?/* If lazy disable, re-enable the VFP ready for it to be saved */
>> > ? ? ? ?if (last_VFP_context[ti->cpu] != &ti->vfpstate) {
>> > ? ? ? ? ? ? ? ?fpexc |= FPEXC_EN;
>> > ? ? ? ? ? ? ? ?fmxr(FPEXC, fpexc);
>> > ? ? ? ?}
>> > ? ? ? ?/* If VFP is on, then save state for resumption */
>> > ? ? ? ?if (fpexc & FPEXC_EN) {
>> > ? ? ? ? ? ? ? ?...
>>
>> I think v2 of the patch handles this case correctly:
>> ? ? ? /* save state for resume */
>> ? ? ? if (last_VFP_context[ti->cpu]) {
>> ? ? ? ? ? ? ? printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
>> ? ? ? ? ? ? ? fmxr(FPEXC, fpexc | FPEXC_EN);
>> ? ? ? ? ? ? ? vfp_save_state(last_VFP_context[ti->cpu], fpexc);
>
> This saves fpexc with the enable flag possibly clear.
>
>> ? ? ? ? ? ? ? last_VFP_context[ti->cpu] = NULL;
>> ? ? ? ? ? ? ? fmxr(FPEXC, fpexc & ~FPEXC_EN);
>> ? ? ? }
>>
>> This version enables the VFP if it was not enabled, but saves the
>> original fpexc value.
>
> Which is wrong as I said above.
>
Sorry, I misunderstood. I'll repost with your changes after I get a
chance to test it, or you can commit it yourself.