Re: [PATCH v2 1/2] PM / Domains: Add GENPD_FLAG_NO_SUSPEND/RESUME flags

From: Sibi Sankar <sibis@codeaurora.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stephen Boyd <swboyd@chromium.org>
Cc: khilman@kernel.org, ulf.hansson@linaro.org, rjw@rjwysocki.net,
	agross@kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
	gregkh@linuxfoundation.org, pavel@ucw.cz, len.brown@intel.com,
	rnayak@codeaurora.org, dianders@chromium.org, mka@chromium.org,
	linux-kernel-owner@vger.kernel.org, clew@codeaurora.org
Subject: Re: [PATCH v2 1/2] PM / Domains: Add GENPD_FLAG_NO_SUSPEND/RESUME flags
Date: Thu, 10 Sep 2020 07:10:47 +0000	[thread overview]
Message-ID: <0101017476da3906-412a2e35-dc56-43ee-8644-83a998279c2d-000000@us-west-2.amazonses.com> (raw)
In-Reply-To: <20200825175345.GC3715@yoga>

On 2020-08-25 23:23, Bjorn Andersson wrote:
> On Tue 25 Aug 02:20 CDT 2020, Stephen Boyd wrote:
>> Quoting Bjorn Andersson (2020-08-24 09:42:12)
>> > On Fri 21 Aug 14:41 PDT 2020, Stephen Boyd wrote:
> [..]
>> > > I find it odd that this is modeled as a power domain instead of some
>> > > Qualcomm specific message that the remoteproc driver sends to AOSS. Is
>> > > there some sort of benefit the driver gets from using the power domain
>> > > APIs for this vs. using a custom API?
>> >
>> > We need to send "up" and "down" notifications and this needs to happen
>> > at the same time as other standard resources are enabled/disabled.
>> >
>> > Further more, at the time the all resources handled by the downstream
>> > driver was either power-domains (per above understanding) or clocks, so
>> > it made sense to me not to spin up a custom API.
>> >
>> 
>> So the benefit is not spinning up a custom API? I'm not Ulf, but it
>> looks like this is hard to rationalize about as a power domain. It
>> doesn't have any benefit to model it this way besides to make it
>> possible to turn on with other power domains.
>> 
>> This modem remoteproc drivers isn't SoC agnostic anyway, it relies on
>> SMEM APIs, so standing up another small qmp_remoteproc_booted() and
>> qmp_remoteproc_shutdown() API would avoid adding a genpd flag here 
>> that
>> probably will never be used outside of this corner-case. There is also
>> some get/put EPROBE_DEFER sort of logic to implement, but otherwise it
>> would be possible to do this outside of power domains, and that seems
>> better given that this isn't really a power domain to start with.
> 
> In later platforms a few new users of the AOSS communication interface
> is introduced that certainly doesn't fit any existing API/framework in
> the kernel. So the plan was to pretty much expose qmp_send() to these
> drivers.
> 
> My worry with using this interface is that we'll probably have to come
> up with some DT binding pieces and probably we'll end up adding yet
> another piece of hard coded information in the remoteproc drivers.
> 
> But I'm not against us doing this work in favor of not having to
> introduce a one-off for this corner case.

Bjorn/Stephen,

So the consensus is to stop modelling
aoss load_state as pds and expose qmp_send
to drivers?

> 
> Regards,
> Bjorn

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