Re: Re: [PATCH][RFC] Add support for Epson S1D13806 FB

["Antonino A. Daplas" <adaplas@hotpop.com>]

On Monday 14 March 2005 22:35, Paul Mundt wrote:
> On Mon, Mar 14, 2005 at 10:10:35PM +0800, Antonino A. Daplas wrote:
> > BTW, I would guess that scrolling is slow in this driver.  Since this
> > driver can do pan_display, If this:
> >
> > info->flags = FBINFO_DEFAULT | FBINFO_HWACCEL_YPAN;
> >
> > is added somewhere before register_framebuffer(), and var->xres_virtual >
> > var->xres, you might get a several-fold increase in scrolling speed
> > (since scrolling mode will be SCROLL_PAN_REDRAW instead of
> > SCROLL_REDRAW).
>
> This is interesting. When FBINFO_HWACCEL_YPAN was added to hitfb, it slowed
> down scrolling by several orders of magnitude. Perhaps it was something
> relating to how the pan_display was implemented, but it's definitely not
> a general win for everyone..

Some hardware waits for vblank/vsync before updating the start address, and
in the case of fbcon, that will be for each row of text. So yes, in this
case, ypan is not a win.

Tony




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