On 19 March 2014 14:47, Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: > Wait, I think I remember. The problem was about dealing with drivers that > do asynchronous notification (those that have the ASYNC_NOTIFICATION flag > set). In particular, exynos-5440 driver sends out the POSTCHANGE notification > from a workqueue worker, much later than sending the PRECHANGE notification. > > From what I saw, this is how the exynos-5440 driver works: > > 1. ->target() is invoked, and the driver writes to a register and returns > to its caller. > > 2. An interrupt occurs that indicates that the frequency was changed. > > 3. The interrupt handler kicks off a worker thread which then sends out > the POSTCHANGE notification. Correct!! > So the important question here is, how does the exynos-5440 driver > protect itself from say 2 ->target() calls which occur in close sequence > (before allowing the entire chain for the first call to complete)? > > As far as I can see there is no such synchronization in the driver at > the moment. Adding Amit to CC for his comments. Yes, and that's what my patch is trying to fix. Where is the confusion? -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
