From: Leo Yan <leo.yan@linaro.org>
To: Andrew Murray <andrew.murray@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
coresight@lists.linaro.org, Sudeep Holla <sudeep.holla@arm.com>,
linux-arm-kernel@lists.infradead.org,
Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH v2 5/5] coresight: etm4x: save/restore state across CPU low power states
Date: Mon, 1 Jul 2019 18:14:40 +0800 [thread overview]
Message-ID: <20190701101440.GD32042@leoy-ThinkPad-X240s> (raw)
In-Reply-To: <20190701095444.GB27745@e119886-lin.cambridge.arm.com>
On Mon, Jul 01, 2019 at 10:54:44AM +0100, Andrew Murray wrote:
> On Mon, Jul 01, 2019 at 05:48:11PM +0800, Leo Yan wrote:
> > On Mon, Jul 01, 2019 at 10:34:58AM +0100, Andrew Murray wrote:
> >
> > [...]
> >
> > > > > In any case, not only do we want to override the firmware to always
> > > > > save/restore. Sometimes we may also want to override the firmware to never
> > > > > save/restore (despite the firmware having the
> > > > > 'arm,coresight-needs-save-restore' flag present). For example to debug power
> > > > > management.
> > > > >
> > > > > Thus with this current approach you can override the firmware to either enable
> > > > > or disable save/restore.
> > > >
> > > > Thanks for explanation and agree with this. Just a suggestion, maybe we
> > > > can initialize 'drvdata->pm_save_enable' in probe as below:
> > > >
> > > > if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE)
> > > > drvdata->pm_save_enable = etm4_needs_save_restore(dev);
> > > > else
> > > > drvdata->pm_save_enable = pm_save_enable;
> > > >
> > > > From then on, we can only use 'drvdata->pm_save_enable' and don't need
> > > > to check the module parameter anymore.
> > >
> > > This is OK, however it means you can't then change the mode once the driver
> > > is probed. I.e. you can't echo values into
> > > /sys/module/coresight-etm4x/pm_save_enable at runtime. This was useful to
> > > me during testing, I assumed it may be useful for others too (especially
> > > given that you can't unload the module).
> >
> > Ah, okay, this is fine for me. Thanks for sharing the knowledge.
>
> Thanks for the review, can I add your Reviewed-By?
Yes, please. Usually, I would like to give a test for patches, this
patch is important for productions after enable CoreSight with CPU
idle; but some platforms are easily to hang after enable CPU idle with
Coresight.
So if you suggest to test this patch set on some public platform, I
can give a testing on it (if I have the boards).
Thanks,
Leo Yan
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next prev parent reply other threads:[~2019-07-01 10:14 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-27 8:35 [PATCH v2 0/5] coresight: etm4x: save/restore ETMv4 context across CPU low power states Andrew Murray
2019-06-27 8:35 ` [PATCH v2 1/5] coresight: etm4x: remove superfluous setting of os_unlock Andrew Murray
2019-06-27 8:35 ` [PATCH v2 2/5] coresight: etm4x: use explicit barriers on enable/disable Andrew Murray
2019-06-27 9:16 ` Suzuki K Poulose
2019-06-27 11:41 ` Andrew Murray
2019-06-28 2:45 ` Leo Yan
2019-06-28 8:35 ` Andrew Murray
2019-06-28 8:51 ` Leo Yan
2019-06-28 9:00 ` Andrew Murray
2019-06-28 9:41 ` Leo Yan
2019-07-01 8:58 ` Suzuki K Poulose
2019-07-01 9:59 ` Leo Yan
2019-06-27 8:35 ` [PATCH v2 3/5] coresight: etm4x: use module_param instead of module_param_named Andrew Murray
2019-06-27 8:35 ` [PATCH v2 4/5] coresight: etm4x: improve clarity of etm4_os_unlock comment Andrew Murray
2019-06-27 8:35 ` [PATCH v2 5/5] coresight: etm4x: save/restore state across CPU low power states Andrew Murray
2019-06-27 14:25 ` Mike Leach
2019-06-27 14:55 ` Andrew Murray
2019-06-27 16:01 ` Suzuki K Poulose
2019-07-08 14:35 ` Andrew Murray
2019-06-28 8:07 ` Leo Yan
2019-06-28 8:53 ` Andrew Murray
2019-06-28 9:12 ` Leo Yan
2019-06-28 9:22 ` Andrew Murray
2019-07-01 2:07 ` Leo Yan
2019-07-01 9:34 ` Andrew Murray
2019-07-01 9:48 ` Leo Yan
2019-07-01 9:54 ` Andrew Murray
2019-07-01 10:14 ` Leo Yan [this message]
2019-07-04 10:21 ` Andrew Murray
2019-07-04 14:27 ` Mathieu Poirier
2019-07-05 1:52 ` Leo Yan
2019-07-01 13:15 ` Suzuki K Poulose
2019-07-04 9:59 ` Andrew Murray
2019-07-03 21:21 ` Mathieu Poirier
2019-07-04 10:06 ` Andrew Murray
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