# \[PATCH\] fb\_defio: add first\_io callback - Subsystems: FRAMEBUFFER LAYER, THE REST - Maintainers: Helge Deller, Linus Torvalds - List: linux-fbdev - 3 messages, 2 authors - Page: https://ratatoskr.run/linux-fbdev/2011/12/13462352/t ## \[PATCH\] fb\_defio: add first\_io callback - From: Heiko Stübner \ - Date: 2011-12-31 10:45:47 - Message: https://ratatoskr.run/linux-fbdev/2011/12/13462352.md ```text 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. Signed-off-by: Heiko Stuebner --- drivers/video/fb_defio.c | 4 ++++ include/linux/fb.h | 1 + 2 files changed, 5 insertions(+), 0 deletions(-) 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 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma, /* 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 diff --git a/include/linux/fb.h b/include/linux/fb.h index 1d6836c..b86cd41 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -602,6 +602,7 @@ struct fb_deferred_io { struct mutex lock; /* mutex that protects the page list */ struct list_head pagelist; /* list of touched pages */ /* callback */ + void (*first_io)(struct fb_info *info); void (*deferred_io)(struct fb_info *info, struct list_head *pagelist); }; #endif -- 1.7.2.3 ``` ## Re: \[PATCH\] fb\_defio: add first\_io callback - From: Florian Tobias Schandinat \ - Date: 2012-02-16 02:27:25 - Message: https://ratatoskr.run/linux-fbdev/2012/02/13462650.md ```text Hi Heiko, sorry for the long delay. On 12/31/2011 10:45 AM, Heiko Stübner wrote: > 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. > > Signed-off-by: Heiko Stuebner while I consider this patch acceptable, I don't see any reason to apply it as long as there is no driver actually using it. Best regards, Florian Tobias Schandinat > --- > drivers/video/fb_defio.c | 4 ++++ > include/linux/fb.h | 1 + > 2 files changed, 5 insertions(+), 0 deletions(-) > > 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 @@ static int fb_deferred_io_mkwrite(struct vm_area_struct *vma, > /* 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 > diff --git a/include/linux/fb.h b/include/linux/fb.h > index 1d6836c..b86cd41 100644 > --- a/include/linux/fb.h > +++ b/include/linux/fb.h > @@ -602,6 +602,7 @@ struct fb_deferred_io { > struct mutex lock; /* mutex that protects the page list */ > struct list_head pagelist; /* list of touched pages */ > /* callback */ > + void (*first_io)(struct fb_info *info); > void (*deferred_io)(struct fb_info *info, struct list_head *pagelist); > }; > #endif ``` ## Re: \[PATCH\] fb\_defio: add first\_io callback - From: Heiko Stübner \ - Date: 2012-02-16 07:34:09 - Message: https://ratatoskr.run/linux-fbdev/2012/02/13462651.md ```text Hi Florian, Am Donnerstag, 16. Februar 2012, 03:27:25 schrieb Florian Tobias Schandinat: > Hi Heiko, > > sorry for the long delay. no problem > On 12/31/2011 10:45 AM, Heiko Stübner wrote: > > 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. > > > > Signed-off-by: Heiko Stuebner > > while I consider this patch acceptable, I don't see any reason to apply it > as long as there is no driver actually using it. ok, so I will keep sitting on it until my driver for the AUO-K190x epd controller is ready for primetime and resubmit this patch in conjunction with it. Heiko ```