diff options
| author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2013-06-12 22:11:18 +0300 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2013-06-13 17:42:04 +0200 |
| commit | e0d8d59b0831523da61739c9d5e3bc3c77d7b5db (patch) | |
| tree | 9a0c0d6ac237d46673b478837a2d8b16ad558510 /drivers/gpu/drm/i915/i915_reg.h | |
| parent | 959e16d65d808602cd88b82530626f964f684c05 (diff) | |
drm/i915: Try harder to disable trickle feed on VLV
The specs are a bit unclear whether the per-plane trickle feed disable
control exists on VLV. There is another trickle feed disable control
in the MI_ARB register.
After some experimentation it turns out both the DSPCNTR trickle feed
bits and the MI_ARB bit can be toggled. However the DSPCNTR bits don't
seem to have any effect.
The MI_ARB bit, on the other hand, has a noticable effect. I performed
an experiment where I reduced the FIFO size via DSPARB and observed the
effect of the MI_ARB trickle feed bit on the display.
Using a 1920x1080-60 mode, with MI_ARB=0x4 the display started to have
problems with DSPARB=0x42424242, whereas with MI_ARB=0x0 the problems
didn't start until DSPARB=0x09090909. This seems to confirm that the
MI_ARB trickle feed bit actually does work.
So replace the use of the DSPCNTR trickle feed bits with MI_ARB
on VLV.
v2: Amend commit message with results from experimentation
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/i915/i915_reg.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_reg.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index 01e8783f1a9..4058eaa1989 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -1367,6 +1367,8 @@ #define FW_BLC_SELF_VLV (VLV_DISPLAY_BASE + 0x6500) #define FW_CSPWRDWNEN (1<<15) +#define MI_ARB_VLV (VLV_DISPLAY_BASE + 0x6504) + /* * Palette regs */ |