re: kern/51339 (No drmkms available for Radeon R7 250)

[matthew green <mrg%eterna.com.au@localhost>]

FWIW, the ati driver disables all acceleration on GCN rev1 chipsets
and the R7 250 is one of these.

i do have X sort of working with an R7 240 which seems very similar
to the 250, except slower and fewer shader + texture cores, but there
is no acceleration.  this is with native xorg-server 1.18 and amd64.

from xf86-video-ati's src/radeon_kms.c:

    833     if (info->ChipFamily >= CHIP_FAMILY_TAHITI) {
    834         goto shadowfb;

    819 shadowfb:
    820         info->r600_shadow_fb = TRUE;

   1627     info->directRenderingEnabled = FALSE;
   1628     if (info->r600_shadow_fb == FALSE)
   1629         info->directRenderingEnabled = radeon_dri2_screen_init(pScreen);

and from radeon_probe.h:

    110     CHIP_FAMILY_TAHITI,
    111     CHIP_FAMILY_PITCAIRN,
    112     CHIP_FAMILY_VERDE,
    113     CHIP_FAMILY_OLAND,

(both the 240 and 250 are OLAND generation.)

i don't know why it has to use shadowfb or why this means no DRI,
but that's what i see in the code of xf86-video-ati 7.7.0.


.mrg.