[alsa-devel] [PATCH v2 0/5] Stripe control functionality

[Pierre-Louis Bossart]

On 1/11/19 11:22 AM, Sameer Pujar wrote:
> Background
> ==========
>
> Azalia Controller fetches command and audio data via DMA and send them
> to codec through SDO(Serial Data Out) lines. SDO is for outboung and it
> broadcasts to all codecs. There is atleast one SDO line present, but
> there can be multiple SDO lines supported for extended bandwidth. This
> is essential when a platform supports multiple hdmi/dp sinks and there
> is a requirement for higher resolution audio playback. In such cases
> simultaneous audio playback data can be striped across multiple SDOs.
>
> Global Capabilities(GCAP) Register indicates the capabilities of the
> controller. Bits 2:1 of GCAP can be read to know the number of supported
> SDO lines (below is from HD audio spec)
>    00: 1 SDO
>    01: 2 SDO
>    10: 4 SDO
>    11: Reserved
>
> Stripe control verb reports and controls the stripe capability of an
> Audio Output Converter. This verb needs to be implemented only for an
> audio output converter and only if the stripe bit of the Audio Widget
> Capabilities parameter is 1.
> Stripe control: get code(0xf24) and set code(0x724)

the series look ok (one minor comment on operator precedence) and 
aligned with my understanding of the HDaudio 1.0a spec.

That said you made no mention of the Stripe bit  (figure 86) and fields 
22:20 (Stripe capability) in Figure 75, so it's not clear to me if the 
support added in this patchset is sufficient or if there is additional 
logic to be set.

There is also a difference between what the controller supports and the 
actual board layout, so it's not clear if the GCAP are really the raw 
capabilities or the ones filtered by BIOS folks to reflect the actual 
platform hardware implementation.

-Pierre