Re: [9fans] ctrl radeon: not working for ATI Radeon 9600 Mobility?

[Venkatesh Srinivas <me@endeavour.zapto.org>]

On Sat, May 1, 2010 at 10:08 AM, erik quanstrom <quanstro@quanstro.net> wrote:
>> erik quanstrom wrote:
>> > i think it's mainly a question of getting the best graphics
>> > performance.  but these days the 2d accelleration (especially
>> > for radeon) is fairly poor.
>>
>> Do you happen to have any workloads where this is a problem? There is
>> a lot more we can do for the radeon, particularly the r100-r300 chips,
>> which could improve draw performance.
>
> i didn't make it clear that i'm using the vesa
> interface.  and it's very slow for every day
> use with acme, but it sure displays pictures quickly.
>
> ; pci | grep vid | grep 1002
> 1.5.0:  vid  03.00.00 1002/791e  10 0:d800000c 134217728 1:00000000 16 2:fbff0004 65536 3:00000000 16 4:0000a001 256 5:fbe00000 1048576
> ; pci 1002/791e
> 1002/791e
>        ATI Technologies Inc RS690 [Radeon X1200 Series]
>
>> To ask the radeon gpu to do anything interesting for you, you must
>> carry out a series of register writes - for example, to fill a
>> rectangle with a solid color, you write the rectangle's color to
>> DP_BRUSH_FGRD_CLR (register 0x147c), the start to DST_X_Y, and the
>> width and height to DST_WIDTH_HEIGHT. Everything you can ask the
>> radeon to do is ultimately done via register writes.
>
> i wonder if this pio doesn't explain a lot of the slowness.
> i would have thought that they would have used a ring.

There is a command processor on the radeon, which we do not
initialize; it can share a ring of commands with the host; it can also
accept indirect buffers. If the radeon driver (on supported h/w) was
too slow for general work, then we could use it, but if its fine right
now, there is no need.

If we really needed speed, we could go further - currently plan9 video
drivers can only accelerate fill and scroll, but in principle the draw
path could use any other functionality the card was willing to do for
it; for the earlier radeons, the 2D engine can do a lot... for the
later ones, we could use the 3d engine in the same style as X's EXA.

-- vs