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| author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2023-06-06 22:15:02 +0300 |
|---|---|---|
| committer | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2023-09-27 18:49:06 +0300 |
| commit | f83b94d23770c234cdc51a1468b3ce9d7e42f20e (patch) | |
| tree | 41eeae6423f5b11496d274a2171ce0bb27553fb0 /drivers/gpu/drm/i915/display/intel_dsb.h | |
| parent | 77d8285683d81321cac88a4d6cdb08f1b205f432 (diff) | |
| download | lwn-f83b94d23770c234cdc51a1468b3ce9d7e42f20e.tar.gz lwn-f83b94d23770c234cdc51a1468b3ce9d7e42f20e.zip | |
drm/i915/dsb: Use DEwake to combat PkgC latency
Normally we could be in a deep PkgC state all the way up to the
point when DSB starts its execution at the transcoders undelayed
vblank. The DSB will then have to wait for the hardware to
wake up before it can execute anything. This will waste a huge
chunk of the vblank time just waiting, and risks the DSB execution
spilling into the vertical active period. That will be very bad,
especially when programming the LUTs as the anti-collision logic
will cause DSB to corrupt LUT writes during vertical active.
To avoid these problems we can instruct the DSB to pre-wake the
display engine on a specific scanline so that everything will
be 100% ready to go when we hit the transcoder's undelayed vblank.
One annoyance is that the scanline is specified as just that,
a single scanline. So if we happen to start the DSB execution
after passing said scanline no DEwake will happen and we may drop
back into some PkgC state before reaching the transcoder's undelayed
vblank. To prevent that we'll use the "force DEwake" bit to manually
force the display engine to stay awake. We'll then have to clear
the force bit again after the DSB is done (the force bit remains
effective even when the DSB is otherwise disabled).
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230606191504.18099-18-ville.syrjala@linux.intel.com
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Diffstat (limited to 'drivers/gpu/drm/i915/display/intel_dsb.h')
| -rw-r--r-- | drivers/gpu/drm/i915/display/intel_dsb.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h b/drivers/gpu/drm/i915/display/intel_dsb.h index 54e9e1dc31ee..16d80f434356 100644 --- a/drivers/gpu/drm/i915/display/intel_dsb.h +++ b/drivers/gpu/drm/i915/display/intel_dsb.h @@ -11,9 +11,10 @@ #include "i915_reg_defs.h" struct intel_crtc; +struct intel_crtc_state; struct intel_dsb; -struct intel_dsb *intel_dsb_prepare(struct intel_crtc *crtc, +struct intel_dsb *intel_dsb_prepare(const struct intel_crtc_state *crtc_state, unsigned int max_cmds); void intel_dsb_finish(struct intel_dsb *dsb); void intel_dsb_cleanup(struct intel_dsb *dsb); |