Re: [PATCH 0/5] ALSA: hda / ASoC: SOF: Add support for PIO command mode

[Péter Ujfalusi <peter.ujfalusi@xxxxxxxxxxxxxxx>]

Hi Jaroslav,

On 09/04/2024 11:53, Jaroslav Kysela wrote:
> On 09. 04. 24 10:38, Peter Ujfalusi wrote:
>> Hi,
>>
>> This series will introduce support for using PIO for commands (immediate
>> commands) instead of CORB while retaining the use of RIRB for unsolicited
>> responses (notifications).
> 
> Hi,
> 
> Could you elaborate, how this affects CPU usage (busy loops for I/O)? Do
> the bus read operation wait until the data transfer on bus is finished?
> 
>> This mode of operation is the recommended one for Lunar Lake family.
> 
> A bit more explanation, please. It looks like a step back.

LunarLake is a different architecture compared to previous solutions, so
some things are improved with e.g. all audio interfaces using the
HDaudio DMA, and others are done differently (commands, wakes, etc).
In practice, we have not found any cases where performance would be
significantly impacted by the use of PIO v. DMA. The number of 'verbs'
sent is usually fairly limited.

The major concern we had initially was firmware download for Cirrus/TI
amps behind an HDaudio bridge, but all of those solutions rely on a side
I2C/SPI bus so the firmware does not rely on the HDaudio commands.
Hope this answers to your questions

-- 
Péter