drm/i915: Program PFI credits for VLV
authorVidya Srinivas <vidya.srinivas@intel.com>
Thu, 5 Mar 2015 19:19:50 +0000 (21:19 +0200)
committerDaniel Vetter <daniel.vetter@ffwll.ch>
Tue, 17 Mar 2015 21:30:15 +0000 (22:30 +0100)
commit1e69cd74af22cce3b882b155bef295ff68a40566
tree5e1ad79b38f0e6bacff7b7ab306ce6e7b7fff2bc
parentae80152ddad252f33893b92dd69f00cc53c5949f
drm/i915: Program PFI credits for VLV

PFI credit programming is required when CD clock (related to data flow from
display pipeline to end display) is greater than CZ clock (related to data
flow from memory to display plane). This programming should be done when all
planes are OFF to avoid intermittent hangs while accessing memory even from
different Gfx units (not just display).

If cdclk/czclk >=1, PFI credits could be set as any number. To get better
performance, larger PFI credit can be assigned to PND. Otherwise if
cdclk/czclk<1, the default PFI credit of 8 should be set.

v2:
    - Change log to lower log level instead of DRM_ERROR
    - Change function name to valleyview_program_pfi_credits
    - Move program PFI credits to modeset_init instead of intel_set_mode
    - Change magic numbers to logical constants

[vsyrjala v3:
 - only program in response to cdclk update
 - program the credits also when cdclk<czclk
 - add CHV bits
 v4:
 - Change CHV cdclk<czclk credits to 12 (Vijay)]

Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
Signed-off-by: Gajanan Bhat <gajanan.bhat@intel.com>
Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Vijay Purushothaman <vijay.a.purushothaman@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
drivers/gpu/drm/i915/i915_reg.h
drivers/gpu/drm/i915/intel_display.c