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drm/i915: W/A for underruns with WM1+ disabled on icl

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Disabling WM1+ on ICL causes tons of underruns with
linear/X-tiled framebuffers. We can avoid this by flipping
on a chicken bit affecting the way the hw fill the FIFO.
This may not be the final solution but should hopefully
avoid some underruns in the meantime.

v2: Apparently PIPE_CHICKEN is icl+ only

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190204202232.27153-1-ville.syrjala@linux.intel.com
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
This commit is contained in:
Ville Syrjälä 2019-02-04 22:22:32 +02:00
parent 108d14bdae
commit bf002c1007
2 changed files with 7 additions and 0 deletions
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1
drivers/gpu/drm/i915/i915_reg.h
View file

@ -7618,6 +7618,7 @@ enum {
#define _PIPEB_CHICKEN 0x71038
#define _PIPEC_CHICKEN 0x72038
#define PER_PIXEL_ALPHA_BYPASS_EN (1 << 7)
#define PM_FILL_MAINTAIN_DBUF_FULLNESS (1 << 0)
#define PIPE_CHICKEN(pipe) _MMIO_PIPE(pipe, _PIPEA_CHICKEN,\
_PIPEB_CHICKEN)

6
drivers/gpu/drm/i915/intel_display.c
View file

@ -3911,6 +3911,12 @@ static void icl_set_pipe_chicken(struct intel_crtc *crtc)
*/
tmp |= PER_PIXEL_ALPHA_BYPASS_EN;
/*
* W/A for underruns with linear/X-tiled with
* WM1+ disabled.
*/
tmp |= PM_FILL_MAINTAIN_DBUF_FULLNESS;
I915_WRITE(PIPE_CHICKEN(pipe), tmp);
}