who knows how long that will take to complete. So the wmb() is not really what we want. Worse, the wmb() is indiscriminate; it will cause the ARM to flush any other unrelated buffered writes and wait for the local interconnect to acknowledge them - potentially very expensive. This first problem could be fixed by doing a readback of the same PRM/CM/SCM register. Since these devices use a single OCP thread, this will cause the MPU to wait for the write to complete. But the primary problem is a conceptual one: clk_disable() should not need any kind of barrier. clk_enable() needs one since device driver code must not access a device until its clocks are known to be enabled. But clk_disable() has no such restriction. Since blocking the MPU on a PRM/CM/SCM write can be a very high-latency operation - several hundred MPU cycles - it's worth avoiding this barrier if possible. linux-omap source commit is f4aacad2c0ed1055622d5c1e910befece24ef0e2. Signed-off-by: Paul Walmsley Signed-off-by: Tony Lindgren Signed-off-by: Russell King 懥*nxUj