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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Saravana Kannan <saravanak@google.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
	Stephen Boyd <sboyd@kernel.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Georgi Djakov <georgi.djakov@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	"Sweeney, Sean" <seansw@qti.qualcomm.com>,
	David Dai <daidavid1@codeaurora.org>,
	adharmap@codeaurora.org, Rajendra Nayak <rnayak@codeaurora.org>,
	Sibi Sankar <sibis@codeaurora.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Evan Green <evgreen@chromium.org>,
	Android Kernel Team <kernel-team@android.com>,
	Linux PM <linux-pm@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 2/3] OPP: Add support for bandwidth OPP tables
Date: Fri, 10 Jan 2020 12:24:20 +0530	[thread overview]
Message-ID: <20200110065420.3bp4fjj2wbezoyrc@vireshk-i7> (raw)
In-Reply-To: <CAGETcx_1B8AfxBuJ9Mbq8BNx-fYyP8pOnF6caN=ooyPARaaJ3A@mail.gmail.com>

On 09-01-20, 10:35, Saravana Kannan wrote:
> Agreed for the example you are giving where PM domains/voltages are
> dropped automatically when dropping the device freq to suspend freq.
> I'm just wondering about a different scenario where if some power
> domain needed to be at say 0.5v when it's suspended (no consumer using
> it)

The domain should be powered off in this case I think.

> to not lose state, or to come back up without brownouts, etc then
> suspend OPP for PM domains might be useful. But I don't know enough
> about that to speak with authority, so I'll leave it at this.
> 
> I see this suspend-opp as a way to mark to what level the bandwidth
> needs to be dropped to/brought back up from during suspend/resume by
> the driver making interconnect bandwidth requests. For example, what
> if the CPU -> DDR needed to be at some level to avoid suspend/resume
> issues (say CPU bug with respect to timing/latencies)? In this
> example, the CPU driver would be the one making bandwidth requests for
> CPU -> DDR bandwidth during normal operation and during
> suspend/resume. So it's basically exactly the same way it would treat
> CPU freq OPP.

I understand your concerns but to me it all looks hypothetical right
now. I am not saying we won't support suspend-opp for interconnect or
domains, but that we should do it only if it is required.

> Btw, I don't have a strong opinion on this. But, even if we do only a
> rate comparison, what does it even mean to compare rates for genpd or
> BW opp tables?

We will never do the comparison because those tables will never have
the suspend OPP in the respective tables.

-- 
viresh

  reply	other threads:[~2020-01-10  6:54 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-07  0:24 [PATCH v6 0/3] Introduce Bandwidth OPPs for interconnects Saravana Kannan
2019-12-07  0:24 ` [PATCH v6 1/3] dt-bindings: opp: Introduce opp-peak-kBps and opp-avg-kBps bindings Saravana Kannan
2020-01-08 10:32   ` Viresh Kumar
2020-01-09  0:32     ` Saravana Kannan
2019-12-07  0:24 ` [PATCH v6 2/3] OPP: Add support for bandwidth OPP tables Saravana Kannan
2020-01-07 19:28   ` Sibi Sankar
2020-01-08  6:16     ` Saravana Kannan
2020-01-29 13:40       ` Sibi Sankar
2020-01-08 10:53   ` Viresh Kumar
2020-01-09  0:58     ` Saravana Kannan
2020-01-09  4:31       ` Viresh Kumar
2020-01-09 18:35         ` Saravana Kannan
2020-01-10  6:54           ` Viresh Kumar [this message]
2019-12-07  0:24 ` [PATCH v6 3/3] OPP: Add helper function " Saravana Kannan
2020-01-08 11:19   ` Viresh Kumar
2020-01-09  0:58     ` Saravana Kannan
2020-01-09  3:36       ` Saravana Kannan
2020-01-09  4:41         ` Viresh Kumar
2020-01-09  4:40       ` Viresh Kumar
2020-01-09 18:44         ` Saravana Kannan
2020-01-10  7:01           ` Viresh Kumar
2020-01-14 10:34 ` [PATCH v6 0/3] Introduce Bandwidth OPPs for interconnects Viresh Kumar

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