On Tuesday, April 07, 2015 at 02:19:33 PM, Geert Uytterhoeven wrote:
> Hi Pavel,
>
> On Tue, Apr 7, 2015 at 2:12 PM, Pavel Machek <pa...@ucw.cz> wrote:
> > I have an socfpga board, which uses has simple framebuffer implemented
> > in the FPGA. On 3.15, framebuffer is fast:
> >
> > root@wagabuibui:~# time cat /dev/fb0 > /dev/null
> > real 0m 0.00s
> > user 0m 0.00s
> > sys 0m 0.00s
> >
> > on 3.18, this takes 220msec. Similar slowdown exists for
> > writes. Simple framebuffer did not change at all between 3.15 and
> > 3.18; resource flags of the framebuffer are still same (0x200).
> >
> > If I enable caching on 3.18, it speeds up a bit, to 70msec or
> > so... Which means problem is not only in caching.
> >
> > Any ideas?
>
> My first guess was commit 67dc0d4758e5 ("vt_buffer: drop console buffer
> copying optimisations"), but this was introduced only in v4.0-rc1.
>
> Just in case you encounter another performance regression after upgrading
> to a more modern kernel ;-)
Why don't you use the Altera VIP FB on SoCFPGA ?
Best regards,
Marek Vasut
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