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