On 12/11/18 12:54 AM, Takashi Iwai wrote:
On Mon, 10 Dec 2018 21:52:05 +0100,
Pierre-Louis Bossart wrote:
On 12/9/18 3:33 AM, Takashi Iwai wrote:
The current HD-audio code manages the DRM audio power via too complex
redirections, and this seems even still unbalanced in a corner case as
Intel DRM CI has been intermittently reporting. This patch is a big
surgery for addressing the complexity and the possible unbalance.
Basically the patch changes the display PM in the following ways:
- Both HD-audio controller and codec drivers call a single helper,
snd_hdac_display_power(). (Formerly, the display power control from
a codec was done indirectly via link_power bus ops.)
- snd_hdac_display_power() receives the codec address index. For
turning on/off from the controller, pass HDA_CODEC_IDX_CONTROLLER.
The need for this virtual index==16 isn't fully clear to me,
especially if you use the bitfields instead of reference counts.
Isn't there a risk of the controller setting the bit16 to zero, but
you still have bit4 on (assuming the idx is 4). If you use this
virtual index, it should override the actual physical bits when
set/cleared.
This is the index for a controller, i.e. we'd need bits for the max
number of codecs + 1.
Actually we do support only up to 8 codecs (HDA_MAX_CODECS), so it
should be 8, instead of 16, too. I'll update to be HDA_MAX_CODECS.
Or is this meant to actually implement a preemption mechanism, where
the display power remains on for as long as the controller wishes,
regardless of what the patch_hdmi and hdac_hdmi code requests?
Right. That's the mechanism at the initial phase, we need the display
power on while probing the codec, i.e. before identifying the codec
ID.
Also don't we already have the HDMI codec address already after the
probe, so couldn't we provide the address directly?
The resume seemed requiring the controller to take the display power
at first, so the same mechanism is used.
ok, makes sense, thanks for the explanations.
So I guess for the SOF patches, the only change would be to add the
second argument HDA_CODEC_IDX_CONTROLLER to snd_hdac_display_power()
calls, the rest looks unchanged or hidden inside the hdac library or
hdac_hdmi parts.
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