On 03/20/2015 05:21 PM, Tomi Valkeinen wrote:
> On 20/03/15 16:57, [email protected] wrote:
>> On 03/20/2015 02:20 PM, Tomi Valkeinen wrote:
>>> On 25/02/15 19:03, [email protected] wrote:
>>>> From: Grygorii Strashko <[email protected]>
>>>>
>>>> Add handling of missed events in omap_dss_pm_notif which are
>>>> needed to support hibernation (suspend to disk).
>>>>
>>>> Signed-off-by: Grygorii Strashko <[email protected]>
>>>> ---
>>>> drivers/video/fbdev/omap2/dss/core.c | 4 ++++
>>>> 1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/video/fbdev/omap2/dss/core.c
>>>> b/drivers/video/fbdev/omap2/dss/core.c
>>>> index 6b74f73..e60976a 100644
>>>> --- a/drivers/video/fbdev/omap2/dss/core.c
>>>> +++ b/drivers/video/fbdev/omap2/dss/core.c
>>>> @@ -178,11 +178,15 @@ static int omap_dss_pm_notif(struct notifier_block
>>>> *b, unsigned long v, void *d)
>>>> DSSDBG("pm notif %lu\n", v);
>>>>
>>>> switch (v) {
>>>> + case PM_HIBERNATION_PREPARE:
>>>> case PM_SUSPEND_PREPARE:
>>>> + case PM_RESTORE_PREPARE:
>>>> DSSDBG("suspending displays\n");
>>>> return dss_suspend_all_devices();
>>>>
>>>> case PM_POST_SUSPEND:
>>>> + case PM_POST_HIBERNATION:
>>>> + case PM_POST_RESTORE:
>>>> DSSDBG("resuming displays\n");
>>>> return dss_resume_all_devices();
>>>>
>>>
>>> Why suspend displays when PM_RESTORE_PREPARE happens? Why resume when
>>> PM_POST_RESTORE happens?
>>
>> We have following sequence when system is restored from hibernation:
>> - original kernel booted;
>> - late_initcall_sync(software_resume);
>> - pm_notifier_call_chain(PM_RESTORE_PREPARE);
>> - freeze_processes
>> - check & read hibernation image
>> - suspend all devices (.freeze())
>> - jump to stored kernel
>> - restore devices
>> ...
>>
>> So, all devices should be in frozen/suspended state when we will jump to
>> stored kernel
>> (device's state should be the same as before creating hib image).
>>
>> Without this patch I can see a lot of log messages like below:
>
> Yes, I am sure a fix is needed for hibernation. But I still don't quite
> understand PM_RESTORE_PREPARE and PM_POST_RESTORE.
>
> When we enter hibernation, there's only PM_HIBERNATION_PREPARE?
No. There is always PM_POST_HIBERNATION:
- original Kernel in case of failure
- restored Kernel on success
>
> When waking from hibernation, there's first PM_RESTORE_PREPARE, where we
> need to disable displays that were enabled during boot. Then either
> PM_POST_HIBERNATION if all went well, or PM_POST_RESTORE if there was an
> error, and in both cases we want to enable the displays?
Yes.
====
int hibernate(void)
error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
...
error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
^^^ restored kernel will start from here
if (error || freezer_test_done)
goto Free_bitmaps;
if (in_suspend) {
...
pr_debug("PM: writing image.\n");
error = swsusp_write(flags);
swsusp_free();
if (!error)
power_down();
in_suspend = 0;
pm_restore_gfp_mask();
^^ this part will be executed by Kernel requested Hibernation
} else {
pr_debug("PM: Image restored successfully.\n");
^^ this part will be executed by Kernel restored from
Hibernation
}
...
pm_notifier_call_chain(PM_POST_HIBERNATION);
^^^ Both Kernels will be notified here:
- original Kernel in case of failure
- restored Kernel on success
====
static int software_resume(void)
error = pm_notifier_call_chain(PM_RESTORE_PREPARE);
error = swsusp_read(&flags);
swsusp_close(FMODE_READ);
if (!error)
hibernation_restore(flags & SF_PLATFORM_MODE);
^^^ if ok we will never return from this function
printk(KERN_ERR "PM: Failed to load hibernation image, recovering.\n");
pm_notifier_call_chain(PM_POST_RESTORE);
^^^
if fail - just continue work as usual
--
regards,
-grygorii
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