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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
	Stephen Boyd <sboyd@kernel.org>,
	linux-pm@vger.kernel.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	Sibi Sankar <sibis@codeaurora.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 03/13] opp: Keep track of currently programmed OPP
Date: Mon, 25 Jan 2021 08:42:29 +0530	[thread overview]
Message-ID: <20210125031229.adthgnbzlcpt4btj@vireshk-i7> (raw)
In-Reply-To: <8af5abe4-fc3f-8ce4-ff14-542754f0275d@gmail.com>

On 22-01-21, 17:31, Dmitry Osipenko wrote:
> This may not be true for all kinds of hardware, a display controller is
> one example. If display's pixclock is raised before the memory bandwidth
> of the display's memory client, then display controller may get a memory
> underflow since it won't be able to fetch memory fast enough and it's
> not possible to pause data transmission to display panel, hence display
> panel may get out of sync and a full hardware reset will be needed in
> order to recover. At least this is the case for NVIDIA Tegra SoCs.

Hmm, but I expected that the request for more data will only come after the
opp-set-rate has finished and not in between. May be I am wrong. There is
nothing wrong in doing it the regulator way if required.

> I guess it's not a real problem for any of OPP API users right now, but
> this is something to keep in mind.

Sure, I am not against it. Just that we thought it isn't worth the code.

-- 
viresh

WARNING: multiple messages have this Message-ID
From: Viresh Kumar <viresh.kumar@linaro.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Nishanth Menon <nm@ti.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-pm@vger.kernel.org, Stephen Boyd <sboyd@kernel.org>,
	Viresh Kumar <vireshk@kernel.org>,
	Rafael Wysocki <rjw@rjwysocki.net>,
	linux-kernel@vger.kernel.org, Sibi Sankar <sibis@codeaurora.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 03/13] opp: Keep track of currently programmed OPP
Date: Mon, 25 Jan 2021 08:42:29 +0530	[thread overview]
Message-ID: <20210125031229.adthgnbzlcpt4btj@vireshk-i7> (raw)
In-Reply-To: <8af5abe4-fc3f-8ce4-ff14-542754f0275d@gmail.com>

On 22-01-21, 17:31, Dmitry Osipenko wrote:
> This may not be true for all kinds of hardware, a display controller is
> one example. If display's pixclock is raised before the memory bandwidth
> of the display's memory client, then display controller may get a memory
> underflow since it won't be able to fetch memory fast enough and it's
> not possible to pause data transmission to display panel, hence display
> panel may get out of sync and a full hardware reset will be needed in
> order to recover. At least this is the case for NVIDIA Tegra SoCs.

Hmm, but I expected that the request for more data will only come after the
opp-set-rate has finished and not in between. May be I am wrong. There is
nothing wrong in doing it the regulator way if required.

> I guess it's not a real problem for any of OPP API users right now, but
> this is something to keep in mind.

Sure, I am not against it. Just that we thought it isn't worth the code.

-- 
viresh

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  reply	other threads:[~2021-01-25  3:13 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-21 11:17 [PATCH 00/13] opp: Implement dev_pm_opp_set_opp() Viresh Kumar
2021-01-21 11:17 ` Viresh Kumar
2021-01-21 11:17 ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 01/13] opp: Rename _opp_set_rate_zero() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 02/13] opp: No need to check clk for errors Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 03/13] opp: Keep track of currently programmed OPP Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 21:41   ` Dmitry Osipenko
2021-01-21 21:41     ` Dmitry Osipenko
2021-01-22  4:45     ` Viresh Kumar
2021-01-22  4:45       ` Viresh Kumar
2021-01-22 14:31       ` Dmitry Osipenko
2021-01-22 14:31         ` Dmitry Osipenko
2021-01-25  3:12         ` Viresh Kumar [this message]
2021-01-25  3:12           ` Viresh Kumar
2021-01-27 16:31       ` Akhil P Oommen
2021-01-28  4:14         ` Viresh Kumar
2021-01-28  4:14           ` Viresh Kumar
2021-07-07 10:24   ` Ionela Voinescu
2021-07-07 10:24     ` Ionela Voinescu
2021-07-08  7:53     ` Viresh Kumar
2021-07-08  7:53       ` Viresh Kumar
2021-07-09  8:57       ` Ionela Voinescu
2021-07-09  8:57         ` Ionela Voinescu
2021-07-12  4:14         ` Viresh Kumar
2021-07-12  4:14           ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 04/13] opp: Split _set_opp() out of dev_pm_opp_set_rate() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 05/13] opp: Allow _set_opp() to work for non-freq devices Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 06/13] opp: Allow _generic_set_opp_regulator() " Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 07/13] opp: Allow _generic_set_opp_clk_only() " Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 20:26   ` Dmitry Osipenko
2021-01-21 20:26     ` Dmitry Osipenko
2021-01-22  4:35     ` Viresh Kumar
2021-01-22  4:35       ` Viresh Kumar
2021-01-25 21:09       ` Dmitry Osipenko
2021-01-25 21:09         ` Dmitry Osipenko
2021-01-27  6:58         ` Viresh Kumar
2021-01-27  6:58           ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 08/13] opp: Update parameters of _set_opp_custom() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 09/13] opp: Implement dev_pm_opp_set_opp() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 10/13] cpufreq: qcom: Migrate to dev_pm_opp_set_opp() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 11/13] devfreq: tegra30: " Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 21:36   ` Dmitry Osipenko
2021-01-21 21:36     ` Dmitry Osipenko
2021-01-22  6:26     ` Viresh Kumar
2021-01-22  6:26       ` Viresh Kumar
2021-01-22 15:28       ` Dmitry Osipenko
2021-01-22 15:28         ` Dmitry Osipenko
2021-01-25  3:14         ` Viresh Kumar
2021-01-25  3:14           ` Viresh Kumar
2021-01-25 16:00           ` Dmitry Osipenko
2021-01-25 16:00             ` Dmitry Osipenko
2021-01-27  9:10   ` [PATCH V2 " Viresh Kumar
2021-01-27 10:02     ` Viresh Kumar
2021-01-27 15:58       ` Dmitry Osipenko
2021-01-28  7:01         ` Viresh Kumar
2021-02-01  0:21     ` Chanwoo Choi
2021-02-01 19:57     ` Dmitry Osipenko
2021-01-21 11:17 ` [PATCH 12/13] drm: msm: " Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar
2021-01-21 11:17 ` [PATCH 13/13] opp: Remove dev_pm_opp_set_bw() Viresh Kumar
2021-01-21 11:17   ` Viresh Kumar

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