From: Rex-BC Chen <rex-bc.chen@mediatek.com>
To: Kevin Hilman <khilman@baylibre.com>, <rafael@kernel.org>,
<viresh.kumar@linaro.org>, <robh+dt@kernel.org>,
<krzk+dt@kernel.org>
Cc: <matthias.bgg@gmail.com>, <jia-wei.chang@mediatek.com>,
<roger.lu@mediatek.com>, <hsinyi@google.com>,
<linux-pm@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-mediatek@lists.infradead.org>,
<Project_Global_Chrome_Upstream_Group@mediatek.com>
Subject: Re: [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU
Date: Mon, 11 Apr 2022 19:51:18 +0800 [thread overview]
Message-ID: <f4c5177fe99cc62b78083d3e8192d97065b2dad2.camel@mediatek.com> (raw)
In-Reply-To: <7hfsmn5m9f.fsf@baylibre.com>
On Fri, 2022-04-08 at 13:54 -0700, Kevin Hilman wrote:
> Rex-BC Chen <rex-bc.chen@mediatek.com> writes:
>
> > From: Jia-Wei Chang <jia-wei.chang@mediatek.com>
> >
> > In some MediaTek SoCs, like MT8183, CPU and CCI share the same
> > power
> > supplies. Cpufreq needs to check if CCI devfreq exists and wait
> > until
> > CCI devfreq ready before scaling frequency.
> >
> > - Add is_ccifreq_ready() to link CCI device to CPI, and CPU will
> > start
> > DVFS when CCI is ready.
> > - Add platform data for MT8183.
> >
> > Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.com>
>
> The checks here are not enough, and will lead to unexpected behavior.
> IIUC, before doing DVFS, you're checking:
>
> 1) if the "cci" DT node is present and
> 2) if the driver for that device is bound
>
> If both those conditions are not met, you don't actually fail, you
> just
> silently do nothing in ->set_target(). As Angelo pointed out also,
> this
> is not a good idea, and will be rather confusing to users.
>
> The same thing would happen if the cci DT node was present, but the
> CCI
> devfreq driver was disabled. Silent failure would also be quite
> unexpected behavior. Similarily, if the cci DT node is not present
> at
> all (like it is in current upstream DT), this CPUfreq driver will
> silently do nothing. Not good.
>
> So, this patch needs to handle several scenarios:
>
> 1) CCI DT node not present
>
> In this case, the driver should still operate normally. With no CCI
> node, or driver there's no conflict.
>
> 2) CCI DT present/enabled but not yet bound
>
> In this case, you could return -EAGAIN as suggested by Angelo, or
> maybe
> better, it should do a deferred probe.
>
> 3) CCI DT present, but driver disabled
>
> This case is similar to (1), this driver should continue to work.
>
> Kevin
Hello Kevin,
Thanks for your review.
I will review these three situations and do some modification.
BRs,
Rex
next prev parent reply other threads:[~2022-04-11 11:51 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 4:58 [PATCH V2 00/15] cpufreq: mediatek: Cleanup and support MT8183 and MT8186 Rex-BC Chen
2022-04-08 4:58 ` [PATCH V2 01/15] dt-bindings: cpufreq: mediatek: Add MediaTek CCI property Rex-BC Chen
2022-04-08 8:10 ` Krzysztof Kozlowski
2022-04-08 10:24 ` Rex-BC Chen
2022-04-08 11:49 ` Krzysztof Kozlowski
2022-04-11 6:48 ` Rex-BC Chen
2022-04-08 4:58 ` [PATCH V2 02/15] cpufreq: mediatek: Use module_init and add module_exit Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 3:17 ` Viresh Kumar
2022-04-08 4:58 ` [PATCH V2 03/15] cpufreq: mediatek: Cleanup variables and error handling in mtk_cpu_dvfs_info_init() Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 3:20 ` Viresh Kumar
2022-04-08 4:58 ` [PATCH V2 04/15] cpufreq: mediatek: Remove unused headers Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 3:21 ` Viresh Kumar
2022-04-08 4:58 ` [PATCH V2 05/15] cpufreq: mediatek: Enable clocks and regulators Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 3:22 ` Viresh Kumar
2022-04-08 4:58 ` [PATCH V2 06/15] cpufreq: mediatek: Record previous target vproc value Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 11:35 ` Rex-BC Chen
2022-04-11 3:26 ` Viresh Kumar
2022-04-11 11:33 ` Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 08/15] cpufreq: mediatek: Move voltage limits to platform data Rex-BC Chen
2022-04-08 13:36 ` AngeloGioacchino Del Regno
2022-04-11 11:18 ` Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 09/15] cpufreq: mediatek: Add .get function Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 10/15] cpufreq: mediatek: Make sram regulator optional Rex-BC Chen
2022-04-08 13:37 ` AngeloGioacchino Del Regno
2022-04-08 20:32 ` Kevin Hilman
2022-04-14 10:53 ` Rex-BC Chen
2022-04-14 17:20 ` Kevin Hilman
2022-04-08 4:59 ` [PATCH V2 11/15] cpufreq: mediatek: Update logic of voltage_tracking() Rex-BC Chen
2022-04-08 21:08 ` Kevin Hilman
2022-04-14 11:30 ` Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 12/15] cpufreq: mediatek: Use maximum voltage in init stage Rex-BC Chen
2022-04-08 13:37 ` AngeloGioacchino Del Regno
2022-04-12 11:24 ` Rex-BC Chen
2022-04-14 3:40 ` Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 13/15] cpufreq: mediatek: Link CCI device to CPU Rex-BC Chen
2022-04-08 13:37 ` AngeloGioacchino Del Regno
2022-04-11 11:50 ` Rex-BC Chen
2022-04-08 20:54 ` Kevin Hilman
2022-04-11 11:51 ` Rex-BC Chen [this message]
2022-04-11 12:31 ` Rex-BC Chen
2022-04-11 18:13 ` Kevin Hilman
2022-04-12 12:26 ` Rex-BC Chen
2022-04-12 18:50 ` Kevin Hilman
2022-04-13 11:32 ` Rex-BC Chen
2022-04-13 21:41 ` Kevin Hilman
2022-04-14 2:32 ` Rex-BC Chen
2022-04-14 21:48 ` Kevin Hilman
2022-04-15 2:31 ` Rex-BC Chen
2022-04-19 18:16 ` Kevin Hilman
2022-04-08 4:59 ` [PATCH V2 14/15] cpufreq: mediatek: Add support for MT8186 Rex-BC Chen
2022-04-08 13:37 ` AngeloGioacchino Del Regno
2022-04-08 21:10 ` Kevin Hilman
2022-04-11 11:14 ` Rex-BC Chen
2022-04-08 4:59 ` [PATCH V2 15/15] cpufreq: mediatek: Use device print to show logs Rex-BC Chen
2022-04-08 13:37 ` AngeloGioacchino Del Regno
2022-04-11 3:29 ` Viresh Kumar
2022-04-11 11:09 ` Rex-BC Chen
[not found] ` <20220408045908.21671-8-rex-bc.chen@mediatek.com>
2022-04-08 13:36 ` [PATCH V2 07/15] cpufreq: mediatek: Add opp notification for SVS support AngeloGioacchino Del Regno
2022-04-08 20:29 ` Kevin Hilman
[not found] ` <3b7bf25a3da6c8f780c87784c1f796bf1e464238.camel@mediatek.com>
2022-04-11 18:09 ` Kevin Hilman
[not found] ` <dfe2d3e3401a6f2a7be9db4e8a0590d3dd9a6969.camel@mediatek.com>
2022-04-12 18:04 ` Kevin Hilman
2022-04-08 21:11 ` [PATCH V2 00/15] cpufreq: mediatek: Cleanup and support MT8183 and MT8186 Kevin Hilman
2022-04-09 1:05 ` Hsin-Yi Wang
2022-04-11 11:37 ` Rex-BC Chen
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