Hello. On 04/01/2016 01:48 AM, Wolfram Sang wrote:
From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> If we don't clear START generation as soon as possible, it may cause another message to be generated, e.g. when receiving NACK in address phase. To keep the race window as small as possible, we clear it right at the beginning of the interrupt. We don't need any checks since we always want to stop START and STOP generation on the next occasion after we started it. This patch improves the situation but sadly does not completely fix it. It is still to be researched if we can do better given this HW design. Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>Thanks for a great work, Wolfram! We need this patch in -stable kernels. The R-Car audio just doesn't work without it...
Really only this patch?
Well, my "reverse" bisection pointed at it. :-)
IIRC my tests showed that if you don't remove the spinlocks (patch 4), the interrupt latency will already be too high again.
Thank you for the valuable info!
In any case, you'd need to do some careful backporting to rip this out of the whole refactoring series.
Yes, I've already figured that.
But maybe you did that already and have good experiences?
Not yet, I will report back after more backporting/testing. MBR, Sergei
