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
next reply other threads:[~2016-06-29 7:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-29 7:23 Krzysztof Kozlowski [this message]
2016-06-30 16:22 ` clk: Per controller locks (prepare & enable) Javier Martinez Canillas
2016-07-04 8:24 ` Krzysztof Kozlowski
2016-07-04 15:15 ` Javier Martinez Canillas
2016-07-04 15:21 ` Javier Martinez Canillas
2016-07-05 6:33 ` Krzysztof Kozlowski
2016-07-05 13:48 ` Javier Martinez Canillas
2016-07-07 12:06 ` Charles Keepax
2016-07-07 12:42 ` Krzysztof Kozlowski
2016-07-07 16:00 ` Charles Keepax
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