diff options
author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2024-02-07 03:33:34 +0200 |
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committer | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2024-02-16 17:11:29 +0200 |
commit | 79e2ea2eaaa699916ebd74232c8f2ef949f8cb90 (patch) | |
tree | ee5e8f76c5c835f010cb09b856db4a0df7b3f75e /drivers/gpu/drm/i915/display/intel_cdclk.c | |
parent | c0151c695fbefcef816432e00d2f8d427ebf3125 (diff) |
drm/i915/cdclk: Document CDCLK update methods
Add a bit of documentation to briefly explain the methods
by which we can change the CDCLK frequency.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240207013334.29606-5-ville.syrjala@linux.intel.com
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Diffstat (limited to 'drivers/gpu/drm/i915/display/intel_cdclk.c')
-rw-r--r-- | drivers/gpu/drm/i915/display/intel_cdclk.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c index ca00586fdbc8..30dae4fef6cb 100644 --- a/drivers/gpu/drm/i915/display/intel_cdclk.c +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c @@ -63,6 +63,15 @@ * DMC will not change the active CDCLK frequency however, so that part * will still be performed by the driver directly. * + * Several methods exist to change the CDCLK frequency, which ones are + * supported depends on the platform: + * - Full PLL disable + re-enable with new VCO frequency. Pipes must be inactive. + * - CD2X divider update. Single pipe can be active as the divider update + * can be synchronized with the pipe's start of vblank. + * - Crawl the PLL smoothly to the new VCO frequency. Pipes can be active. + * - Squash waveform update. Pipes can be active. + * - Crawl and squash can also be done back to back. Pipes can be active. + * * RAWCLK is a fixed frequency clock, often used by various auxiliary * blocks such as AUX CH or backlight PWM. Hence the only thing we * really need to know about RAWCLK is its frequency so that various |