broadsheetfb and fbcon

broadsheetfb and fbcon

[Robert Emanuele]

Greetings lkml and Jaya,

I've been using the broadsheetfb graphics driver for a while now.
I've been trying to get it working with the fbcon console driver.  Has
anyone had any success with that?

While it "works", its performance is unusable as a console.  It
redraws the whole screen every new line, which may be acceptable.  A
real issue is when it tries to scroll the screen, it redraws each line
partially and then does a full screen update with each partial line.
It seems the driver is capable from Jaya's video at
http://www.youtube.com/watch?v=0Bny6qyRDWw

Are those kind of updates a limit of the broadsheet driver or fbcon?
Or more hopefully, is there a configuration change to improve this?

Thanks for your help,

Rob

Re: broadsheetfb and fbcon

[Konrad Rzeszutek Wilk]

On Sat, Jun 05, 2010 at 04:21:08PM -0700, Robert Emanuele wrote:
> Greetings lkml and Jaya,
> 
> I've been using the broadsheetfb graphics driver for a while now.
> I've been trying to get it working with the fbcon console driver.  Has
> anyone had any success with that?
> 
> While it "works", its performance is unusable as a console.  It
> redraws the whole screen every new line, which may be acceptable.  A
> real issue is when it tries to scroll the screen, it redraws each line
> partially and then does a full screen update with each partial line.
> It seems the driver is capable from Jaya's video at
> http://www.youtube.com/watch?v=0Bny6qyRDWw
> 
> Are those kind of updates a limit of the broadsheet driver or fbcon?

I thought there was an update value on how often it should redraw. Did
you do a modinfo on the driver?
> Or more hopefully, is there a configuration change to improve this?

Re: broadsheetfb and fbcon

[Robert Emanuele]

There are no module parameters for fbcon or broadsheetfb.

On Mon, Jun 7, 2010 at 9:28 AM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> On Sat, Jun 05, 2010 at 04:21:08PM -0700, Robert Emanuele wrote:
>> Greetings lkml and Jaya,
>>
>> I've been using the broadsheetfb graphics driver for a while now.
>> I've been trying to get it working with the fbcon console driver.  Has
>> anyone had any success with that?
>>
>> While it "works", its performance is unusable as a console.  It
>> redraws the whole screen every new line, which may be acceptable.  A
>> real issue is when it tries to scroll the screen, it redraws each line
>> partially and then does a full screen update with each partial line.
>> It seems the driver is capable from Jaya's video at
>> http://www.youtube.com/watch?v=0Bny6qyRDWw
>>
>> Are those kind of updates a limit of the broadsheet driver or fbcon?
>
> I thought there was an update value on how often it should redraw. Did
> you do a modinfo on the driver?
>> Or more hopefully, is there a configuration change to improve this?
>

Re: broadsheetfb and fbcon

[Jaya Kumar]

On Sun, Jun 6, 2010 at 7:21 AM, Robert Emanuele <rob@emanuele.us> wrote:
> real issue is when it tries to scroll the screen, it redraws each line
> partially and then does a full screen update with each partial line.

Sounds like what to expect because fbcon is using the slow path with
synchronous updates. It should be relatively straightforward to
improve that by reusing the deferred handler.

> It seems the driver is capable from Jaya's video at
> http://www.youtube.com/watch?v=0Bny6qyRDWw
>
> Are those kind of updates a limit of the broadsheet driver or fbcon?

That demo was horribly slow because it was host limited by the
xres*yres*16 gpio calls. That video was made before using batch
gpiolib support, which is a patchset that's out of tree,
http://thread.gmane.org/gmane.linux.fbdev.devel/13285 .

I had better results here, http://www.youtube.com/watch?v=aoG7XHO7P0s
and I was able to support 8Hz video,
http://www.youtube.com/watch?v=i4Loe5rIu4I (not display limited but
host limited). I had posted all of the code for that for review on
fbdev a while back, but I decided against getting it merged because it
wasn't elegant (needed userspace changes) and I think we can do
better. I'm trying to find time/funding to make those improvements.

Thanks,
jaya

Re: broadsheetfb and fbcon

[Konrad Rzeszutek Wilk]

On Mon, Jun 07, 2010 at 10:19:27AM -0700, Robert Emanuele wrote:
> There are no module parameters for fbcon or broadsheetfb.
> 
> On Mon, Jun 7, 2010 at 9:28 AM, Konrad Rzeszutek Wilk
> >> Are those kind of updates a limit of the broadsheet driver or fbcon?
> >
> > I thought there was an update value on how often it should redraw. Did
> > you do a modinfo on the driver?

Please do not post your response on top.

What I was thinking about is the delay variable:

1056 static struct fb_deferred_io broadsheetfb_defio = {
1057         .delay          = HZ/4,
1058         .deferred_io    = broadsheetfb_dpy_deferred_io,
1059 };
1060 


Try changing that to a higher number and seeing if that fixes your
problem. If so, you and I can work on a patch that sets a parameter
for this.

Re: broadsheetfb and fbcon

[Robert Emanuele]

On Tue, Jun 8, 2010 at 6:21 AM, Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com> wrote:
> On Mon, Jun 07, 2010 at 10:19:27AM -0700, Robert Emanuele wrote:
>> There are no module parameters for fbcon or broadsheetfb.
>>
>> On Mon, Jun 7, 2010 at 9:28 AM, Konrad Rzeszutek Wilk
>> >> Are those kind of updates a limit of the broadsheet driver or fbcon?
>> >
>> > I thought there was an update value on how often it should redraw. Did
>> > you do a modinfo on the driver?
>
> Please do not post your response on top.
>
> What I was thinking about is the delay variable:
>
> 1056 static struct fb_deferred_io broadsheetfb_defio = {
> 1057         .delay          = HZ/4,
> 1058         .deferred_io    = broadsheetfb_dpy_deferred_io,
> 1059 };
> 1060
>
>
> Try changing that to a higher number and seeing if that fixes your
> problem. If so, you and I can work on a patch that sets a parameter
> for this.
>

Increasing the delay value to a larger value (more updates/sec) or a
smaller value (fewer updates/sec) in the broadsheet driver does not
affect the screen update rate.  Does the fbcon used the deferred io
handler?

Thanks,

Rob