[Intel-gfx] [PATCH v4 0/6] Check pixel clock when setting mode

Mika Kahola mika.kahola at intel.com
Tue Feb 2 13:16:37 UTC 2016

>From EDID we can read and request higher pixel clock than
our HW can support. This set of patches add checks if
requested pixel clock is lower than the one supported by the HW.
The requested mode is discarded if we cannot support the requested
pixel clock. For example for Cherryview

'cvt 2560 1600 60' gives

# 2560x1600 59.99 Hz (CVT 4.10MA) hsync: 99.46 kHz; pclk: 348.50 MHz
Modeline "2560x1600_60.00"  348.50  2560 2760 3032 3504  1600 1603 1609 1658 -hsync +vsync

where pixel clock 348.50 MHz is higher than the supported 304 MHz.

The missing mode validity checks for DisplayPort, HDMI, DP-MST, SDVO, CRT, and TV.

- The maximum DOT clock frequency is added to debugfs i915_frequency_info.
- max dotclock cached in dev_priv structure
- moved computation of max dotclock to 'intel_display.c'

- intel_update_max_dotclk() renamed as intel_compute_max_dotclk()
- for GEN9 and above the max dotclock frequency is equal to CD clock
- for older generations the dot clock frequency is limited to 90% of the
  CD clock frequency
- For Cherryview the dot clock is limited to 95% of CD clock frequency
- for GEN2/3 the maximum dot clock frequency is limited to 90% of the
  2X CD clock frequency as we have on option to use double wide mode
- cleanup

- renaming of max_dotclk as max_dotclk_freq in dev_priv (i915_drv.h)
  caused changes to all patches in my series even though some of them has
  been r-b'd by Ville
- for consistency the max_pixclk variable is renamed as max_dotclk throughout
  the whole series

Mika Kahola (6):
  drm/i915: DisplayPort pixel clock check
  drm/i915: HDMI pixel clock check
  drm/i915: DisplayPort-MST pixel clock check
  drm/i915: SDVO pixel clock check
  drm/i915: CRT pixel clock check
  drm/i915: TV pixel clock check

 drivers/gpu/drm/i915/intel_crt.c    | 4 ++++
 drivers/gpu/drm/i915/intel_dp.c     | 3 ++-
 drivers/gpu/drm/i915/intel_dp_mst.c | 5 +++++
 drivers/gpu/drm/i915/intel_hdmi.c   | 8 ++++++++
 drivers/gpu/drm/i915/intel_sdvo.c   | 4 ++++
 drivers/gpu/drm/i915/intel_tv.c     | 4 ++++
 6 files changed, 27 insertions(+), 1 deletion(-)


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