fb_defio: add first_io callback
With this optional callback the driver is notified when the first page
is entered into the pagelist and a new deferred_io call is scheduled.
A possible use-case for this is runtime-pm. In the first_io call
pm_runtime_get()
could be called, which starts an asynchronous runtime_resume of the
device. In the deferred_io callback a call to
pm_runtime_barrier()
makes the sure, the device is resumed by then and a
pm_runtime_put()
may put the device back to sleep.
Also, some SoCs may use the runtime-pm system to determine if they
are able to enter deeper idle states. Therefore it is necessary to
keep the use-count from the first written page until the conclusion
of the screen update, to prevent the system from going to sleep before
completing the pending update.
Two users of defio were using kmalloc to allocate the structure.
These allocations are changed to kzalloc, to prevent uninitialised
.first_io members in those drivers.
Signed-off-by: Heiko Stübner <heiko@sntech.de>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
diff --git a/drivers/video/fb_defio.c b/drivers/video/fb_defio.c
index c27e153..070f26f 100644
--- a/drivers/video/fb_defio.c
+++ b/drivers/video/fb_defio.c
@@ -107,6 +107,10 @@
/* protect against the workqueue changing the page list */
mutex_lock(&fbdefio->lock);
+ /* first write in this cycle, notify the driver */
+ if (fbdefio->first_io && list_empty(&fbdefio->pagelist))
+ fbdefio->first_io(info);
+
/*
* We want the page to remain locked from ->page_mkwrite until
* the PTE is marked dirty to avoid page_mkclean() being called