From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
To: Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@codeaurora.org>,
linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Tomasz Figa <tomasz.figa@gmail.com>,
Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Andrzej Hajda <a.hajda@samsung.com>,
Javier Martinez Canillas <javier@osg.samsung.com>
Subject: clk: Per controller locks (prepare & enable)
Date: Wed, 29 Jun 2016 09:23:13 +0200 [thread overview]
Message-ID: <57737761.2020708@samsung.com> (raw)
Hi,
Problems:
1. Deadlocks on prepare lock in following scenario:
- prepare_enable(some external clock through i2c)
- i2c transfer
- prepare_enable(i2c lock in SoC)
- deadlock
See [1]. We implemented a workaround for this in few places like
10ff4c5239a1 ("i2c: exynos5: Fix possible ABBA deadlock by keeping I2C
clock prepared") and 34e81ad5f0b6 ("i2c: s3c2410: fix ABBA deadlock by
keeping clock prepared")
The goal would be to remove also this workaround.
2. The global prepare and enable locks are over-used. I didn't test the
congestion but intuition says that they could be improved.
Solution:
Make this locks per controller. This will directly solve problem #1
because these are different controllers. Still in-controller deadlock
could occur but we couldn't find a real case with it.
Question:
What do you think about it? I know that talk is cheap and code looks
better but before starting the work I would like to hear some
comments/opinions/ideas.
Best regards,
Krzysztof
[1]
http://www.krzk.eu/builders/boot-odroid-xu3-multi_v7/builds/34/steps/Boot%20odroid/logs/serial
WARNING: multiple messages have this Message-ID (diff)
From: k.kozlowski@samsung.com (Krzysztof Kozlowski)
To: linux-arm-kernel@lists.infradead.org
Subject: clk: Per controller locks (prepare & enable)
Date: Wed, 29 Jun 2016 09:23:13 +0200 [thread overview]
Message-ID: <57737761.2020708@samsung.com> (raw)
Hi,
Problems:
1. Deadlocks on prepare lock in following scenario:
- prepare_enable(some external clock through i2c)
- i2c transfer
- prepare_enable(i2c lock in SoC)
- deadlock
See [1]. We implemented a workaround for this in few places like
10ff4c5239a1 ("i2c: exynos5: Fix possible ABBA deadlock by keeping I2C
clock prepared") and 34e81ad5f0b6 ("i2c: s3c2410: fix ABBA deadlock by
keeping clock prepared")
The goal would be to remove also this workaround.
2. The global prepare and enable locks are over-used. I didn't test the
congestion but intuition says that they could be improved.
Solution:
Make this locks per controller. This will directly solve problem #1
because these are different controllers. Still in-controller deadlock
could occur but we couldn't find a real case with it.
Question:
What do you think about it? I know that talk is cheap and code looks
better but before starting the work I would like to hear some
comments/opinions/ideas.
Best regards,
Krzysztof
[1]
http://www.krzk.eu/builders/boot-odroid-xu3-multi_v7/builds/34/steps/Boot%20odroid/logs/serial
next reply other threads:[~2016-06-29 7:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-29 7:23 Krzysztof Kozlowski [this message]
2016-06-29 7:23 ` clk: Per controller locks (prepare & enable) Krzysztof Kozlowski
2016-06-30 16:22 ` Javier Martinez Canillas
2016-06-30 16:22 ` Javier Martinez Canillas
2016-07-04 8:24 ` Krzysztof Kozlowski
2016-07-04 8:24 ` Krzysztof Kozlowski
2016-07-04 15:15 ` Javier Martinez Canillas
2016-07-04 15:15 ` Javier Martinez Canillas
2016-07-04 15:21 ` Javier Martinez Canillas
2016-07-04 15:21 ` Javier Martinez Canillas
2016-07-05 6:33 ` Krzysztof Kozlowski
2016-07-05 6:33 ` Krzysztof Kozlowski
2016-07-05 13:48 ` Javier Martinez Canillas
2016-07-05 13:48 ` Javier Martinez Canillas
2016-07-07 12:06 ` Charles Keepax
2016-07-07 12:06 ` Charles Keepax
2016-07-07 12:42 ` Krzysztof Kozlowski
2016-07-07 12:42 ` Krzysztof Kozlowski
2016-07-07 16:00 ` Charles Keepax
2016-07-07 16:00 ` Charles Keepax
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=57737761.2020708@samsung.com \
--to=k.kozlowski@samsung.com \
--cc=a.hajda@samsung.com \
--cc=b.zolnierkie@samsung.com \
--cc=javier@osg.samsung.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-clk@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=mturquette@baylibre.com \
--cc=s.nawrocki@samsung.com \
--cc=sboyd@codeaurora.org \
--cc=tomasz.figa@gmail.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.