]> git.karo-electronics.de Git - karo-tx-linux.git/commit
i2c: designware: wait for disable/enable only if necessary
authorJosé Roberto de Souza <jose.souza@intel.com>
Tue, 23 Aug 2016 22:18:53 +0000 (19:18 -0300)
committerWolfram Sang <wsa@the-dreams.de>
Thu, 25 Aug 2016 22:42:12 +0000 (00:42 +0200)
commit2702ea7dbec55db62fa3016c7275fea7b508033f
treeebe2ced9f736a3ef79e1da1f91e98eb7abf905d0
parent10f8e7fb371c9e575e772bc6fcc385dc973f6e87
i2c: designware: wait for disable/enable only if necessary

If we aren't going to continue using the controller we can just disable
it instead of waiting for it to complete. The biggest improvement here
is when a I2C transaction is completed and it doesn't block until
the adapter is disabled. When a new transfer is needed we will disable
and wait for its completion.

This way the adapter will continue changing its state in parallel to the
execution of the thread that requested the I2C transaction saving most
of the time 25~250 usec per I2C transaction.

A simple program doing a register read (1 byte write, 1 byte read)
alternating on 2 different slaves repeated 25k times for each and
measurements taken 4 times we get:

perf stat -r4 chrt -f 10 ./i2c-test /dev/i2c-1 25000 0x40 0x6 0x1e 0x00

Before:
30.879317977 seconds time elapsed                 ( +- 14.83% )
After:
8.638705161 seconds time elapsed                  ( +-  5.90% )

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Tested-by: Christian Ruppert <christian.ruppert@alitech.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
drivers/i2c/busses/i2c-designware-core.c