From: Mark Brown Date: Wed, 21 Nov 2012 04:12:11 +0000 (+0900) Subject: i2c: s3c2410: Remove recently introduced performance overheads X-Git-Tag: v3.8-rc1~54^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=31f313d9bebfc17e48c787c8c36b38662b4134a1;p=pandora-kernel.git i2c: s3c2410: Remove recently introduced performance overheads The changes in "i2c-s3c2410: use exponential back off while polling for bus idle" remove the initial busy wait for I2C transfers to complete and replace it with usleep_range() calls which will schedule. Since for older SoCs I2C transfers would usually complete within an extremely small number of CPU cycles there is a win from not having to schedule. This happens because on the older SoCs the cores run at a smaller multiple of the speeds that the I2C bus is operating at; on more modern SoCs the busy wait is less likely to be effective. Fix the issue by restoring the busy wait, reducing the number of spins from 20 to 3 which covers the overwhelming majority of I2C transfers on the SoCs where the busy wait is effective. Signed-off-by: Mark Brown Acked-by: Olof Johansson Reviewed-by: Daniel Kurtz Reviewed-by: Doug Anderson Signed-off-by: Wolfram Sang --- Reading git-diff-tree failed