Re: [PATCH 2/4] i915: add support for GPU side of MST audio

Jani Nikula
2015-06-17T11:52:09Z

On Wed, 17 Jun 2015, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> On Wed, Jun 17, 2015 at 02:01:57PM +1000, Dave Airlie wrote:
>> From: Dave Airlie <airlied@redhat.com>
>>
>> This just adds enables for the codecs and debugfs
>> support for mst connectors to print the audio info.
>>
>> This relies on patches to the audio code to do anything
>> more useful.
>>
>> Signed-off-by: Dave Airlie <airlied@redhat.com>
>> ---
>> @@ -231,6 +231,7 @@ static void hsw_audio_codec_enable(struct drm_connector *connector,
>> /* Reset ELD write address */
>> tmp = I915_READ(HSW_AUD_DIP_ELD_CTRL(pipe));
>> tmp &= ~IBX_ELD_ADDRESS_MASK;
>> + tmp |= ((pipe + 1) << 29);
>> I915_WRITE(HSW_AUD_DIP_ELD_CTRL(pipe), tmp);
>
> This is not MST specific. Is this a bug fix we want ASAP?

"""
This read-only bit reflects which port is used to transmit the DIP
data. This can only change when DIP is disabled. If one or more
audio-related DIP packets is enabled and audio is enabled on a digital
port, these bits will reflect the digital port to which audio is
directed.

For DP MST, this is the device select/pipe select.
"""

We shouldn't mess with the field if it's regular DP. Also "pipe + 1" is
too magic; unfortunately I don't know what it should be. :(

BR,
Jani.

> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
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--
Jani Nikula, Intel Open Source Technology Center