[Bug 100439] [GLK] cdclock frequency is always the same

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Wed Mar 29 20:59:22 UTC 2017


https://bugs.freedesktop.org/show_bug.cgi?id=100439

--- Comment #3 from Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com> ---
HDMI audio is being enabled, which restricts cdclk going lower than 2*Azalia
bclk (96 MHz by default). The choices for cdclk on GLK are 316.8 MHz, 158.4 MHz
and 79.2 MHz. So, the only value greater than 2*96 MHz is 316.8 MHz.

>From BSpec
"158.4 MHz CD (cannot be used when audio is enabled and Azalia BCLK is 96 MHz)
316.8 MHz CD
79.2 MHz CD (exclusively for resolutions up to 1080p in low power single pipe
eDP/MIPI configurations, no audio support)"

Not entirely sure what happens if we violate this restriction in practice, but
I think it makes sense to define a new API to get the actual Azalia bclk from
the audio driver and explore options to lower that.

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