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Message-ID: <20161114170444.GP1575@localhost.localdomain>
Date: Mon, 14 Nov 2016 17:04:44 +0000
From: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
CC: Hardik Shah <hardik.t.shah@...el.com>,
<alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
<tiwai@...e.de>, <broonie@...nel.org>, <lgirdwood@...il.com>,
<plai@...eaurora.org>, <patches.audio@...el.com>,
Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [RFC 02/14] SoundWire: Add SoundWire stream documentation
On Mon, Nov 14, 2016 at 10:50:10AM -0600, Pierre-Louis Bossart wrote:
>
> >>+SoundWire stream states
> >>+=======================
> >>+Below figure shows the SoundWire stream states and possible state
> >>+transition diagram.
> >>+
> >>+|--------------| |-------------| |--------------| |--------------|
> >>+| ALLOC |---->| CONFIG |---->| PREPARE |---->| ENABLE |
> >>+| STATE | | STATE | | STATE | | STATE |
> >>+|--------------| |-------------| |--------------| |--------------|
> >>+ ^ |
> >>+ | |
> >>+ | |
> >>+ | |
> >>+ | \/
> >>+ |--------------| |--------------| |--------------|
> >>+ | RELEASE |<--------------------| DEPREPARE |<----| DISABLE |
> >>+ | STATE | | STATE | | STATE |
> >>+ |--------------| |--------------| |--------------|
> >>+
> >
> >One minor comment, this looks very similar to the clock
> >frameworks state model, but the clock framework calls it
> >unprepare would there be some milage in aligning to?
>
> The SoundWire spec uses de-prepare, e.g. "De-prepare_Finished"
> I'd rather stick to the wording between a spec and the implementation of
> said spec, rather than introduce a term/concept from an unrelated framework.
> >
Cool we should leave that as is then :-)
> >>+4. Once all the new values are programmed, bus initiates switch to
> >>+alternate bank. Once switch is successful, the port channels enabled on
> >>+previous bank for already active streams are disabled.
>
> This last sentence makes no sense in this context, probably a copy/paste
> that shouldn't be there. The previously active streams remain active in this
> prepare step.
>
> >>+
> >>+5. Ports of Master and Slave for current stream are prepared.
> >>+
> >>+After all above operations are successful, stream state is set to
> >>+SDW_STATE_STRM_PREPARE.
> >>+
> >>+
> >>+SDW_STATE_STRM_ENABLE: Enable state of stream. Operations performed
> >>+before entering in this state:
> >>+1. All the values computed in SDW_STATE_STRM_PREPARE state are
> >>+programmed in alternate bank (bank currently unused). It includes
> >>+programming of already active streams as well.
> >>+
> >>+2. All the Master and Slave port channels for the current stream are
> >>+enabled on alternate bank (bank currently unused).
> >>+
> >
> >This could probably use a little more explaination to show how it
> >differs from step 3/4 in PREPARE, as it looks like all the
> >computed values where applied there. I imagine this is just my lack
> >of understanding rather than an actual issue but even looking at
> >the code I am having a little difficulty tying up these two.
>
> Yes, see above there was an extra sentence that isn't right.
>
> >
> >sdw_prepare_op
> >- sdw_compute_params (prepare step 1/2)
> >- sdw_program_params (prepare step 3)
> >- sdw_update_bus_params (prepare step 4)
> >
> >sdw_enable_op
> >- sdw_program_params (enable step 1)
> >- sdw_update_bus_params (enable step 2)
> >
> >It looks like the params are still basically the same as they
> >were when we called sdw_program_params in prepare.
>
> The parameters are the same except for the channel-enable flags which are
> only programmed and activated via a bank switch in the enable step.
Ah ok that is what is getting pushed out there, thanks for
explaining.
Thanks,
Charles
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