From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Mike Leach <mike.leach@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arm-msm@vger.kernel.org,
Coresight ML <coresight@lists.linaro.org>,
Stephen Boyd <swboyd@chromium.org>,
robin.murphy@arm.com
Subject: Re: [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF
Date: Wed, 03 Jun 2020 15:54:17 +0530 [thread overview]
Message-ID: <f0357072de96970b641bbd0da98c1d61@codeaurora.org> (raw)
In-Reply-To: <CAJ9a7VhMbdqVBHxEXGYxFkgPnnQqNnDAz=wkHP3s7Ntw0iLmKA@mail.gmail.com>
Hi Mike,
Thanks again for looking at this.
On 2020-06-03 03:42, Mike Leach wrote:
[...]
>>
>> SMMU/IOMMU won't be able to do much here as it is the client's
>> responsiblity to
>> properly shutdown and SMMU device link just makes sure that
>> SMMU(supplier) shutdown is
>> called only after its consumers shutdown callbacks are called.
>
> I think this use case can be handled slightly differently than the
> general requirements for modular CoreSight drivers.
>
> What is needed here is a way of stopping the underlying ETR hardware
> from issuing data to the SMMU, until the entire device has been shut
> down, in a way that does not remove the driver, breaking existing
> references and causing a system crash.
>
> We could introduce a new mode to the ETR driver - e.g.
> CS_MODE_SHUTDOWN.
>
> At the end of the block tmc_shutdown(struct amba_device *adev), set
> drvdata->mode to CS_MODE_SHUTDOWN & remove the coresight_unregister().
> This new mode can be used to prevent the underlying hardware from
> being able to restart until the device is re-powered.
>
> This mode can be detected in the code that enables / disables the ETR
> and handled appropriately (updates to tmc_enable_etr_sink and
> tmc_disable_etr_sink).
> This mode will persist until the device is re-started - but because we
> are on the device shutdown path this is not an issue.
>
> This should leave the CoreSight infrastructure stable until the
> drivers are shut down normally as part of the device power down
> process.
>
Sounds good to me, but if the coresight_unregister() is the trouble
point
causing these crashes, then can't we just remove that from
tmc_shutdown()
callback? This would be like maintaining the same behaviour as now where
on reboot/shutdown we basically don't do anything except for disabling
ETR.
This way, we do not have to introduce any new mode as well. To be exact,
in
tmc_shutdown() we just disable ETR and then return without unregistering
which should not cause any issues since this is shutdown not the remove
callback which is a requirement for making coresight modular like below:
static void tmc_shutdown(struct amba_device *adev)
{
unsigned long flags;
struct tmc_drvdata *drvdata = amba_get_drvdata(adev);
spin_lock_irqsave(&drvdata->spinlock, flags);
if (drvdata->mode == CS_MODE_DISABLED)
goto out;
if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
tmc_etr_disable_hw(drvdata);
/*
* We do not care about coresight unregister here unlike remove
* callback which is required for making coresight modular
since
* the system is going down after this.
*/
out:
spin_unlock_irqrestore(&drvdata->spinlock, flags);
}
Thanks,
Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member
of Code Aurora Forum, hosted by The Linux Foundation
next prev parent reply other threads:[~2020-06-03 10:24 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-01 8:02 [PATCH 0/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF Sai Prakash Ranjan
2020-06-01 8:02 ` [PATCH 1/2] coresight: tmc: Add enable flag to indicate the status of ETR/ETF Sai Prakash Ranjan
2020-06-01 13:27 ` Mike Leach
2020-06-01 17:13 ` Sai Prakash Ranjan
2020-06-01 8:02 ` [PATCH 2/2] coresight: tmc: Add shutdown callback for TMC ETR/ETF Sai Prakash Ranjan
2020-06-01 13:35 ` Mike Leach
2020-06-01 17:15 ` Sai Prakash Ranjan
2020-06-01 21:28 ` Mathieu Poirier
2020-06-02 7:30 ` Sai Prakash Ranjan
2020-06-02 22:12 ` Mike Leach
2020-06-03 10:24 ` Sai Prakash Ranjan [this message]
2020-06-03 11:27 ` Mike Leach
2020-06-03 12:14 ` Sai Prakash Ranjan
2020-06-03 13:22 ` Mike Leach
2020-06-03 13:34 ` Robin Murphy
2020-06-03 13:43 ` Sai Prakash Ranjan
2020-06-03 13:51 ` Mike Leach
2020-06-03 14:02 ` Sai Prakash Ranjan
2020-06-03 17:44 ` Mathieu Poirier
2020-06-04 7:27 ` Sai Prakash Ranjan
2020-06-08 14:07 ` Sai Prakash Ranjan
2020-06-09 15:27 ` Mathieu Poirier
2020-06-09 15:37 ` Sai Prakash Ranjan
2020-06-03 11:37 ` Robin Murphy
2020-06-03 12:00 ` Sai Prakash Ranjan
2020-06-03 12:21 ` Robin Murphy
2020-06-03 12:26 ` Sai Prakash Ranjan
2020-06-03 13:40 ` Robin Murphy
2020-06-03 13:51 ` Sai Prakash Ranjan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f0357072de96970b641bbd0da98c1d61@codeaurora.org \
--to=saiprakash.ranjan@codeaurora.org \
--cc=coresight@lists.linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.poirier@linaro.org \
--cc=mike.leach@linaro.org \
--cc=robin.murphy@arm.com \
--cc=suzuki.poulose@arm.com \
--cc=swboyd@chromium.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).