[PATCH V2 2/5] cpufreq: send new set of notification for transition failures
In the current code, if we fail during a frequency transition we simply send the POSTCHANGE notification with old frequency. This isn't enough. One of the core user of these notifications is the code responsible for keeping loops_per_jiffy aligned with frequency change. And mostly it is written as: if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) { update-loops-per-jiffy... } So, suppose we are changing to a higher frequency and failed during transition, then following will happen: - CPUFREQ_PRECHANGE notification with freq-new > freq-old - CPUFREQ_POSTCHANGE notification with freq-new == freq-old The first one will update loops_per_jiffy and second one will do nothing. Even if we send the 2nd notification by exchanging values of freq-new and old, some users of these notifications might get unstable. This can be fixed by simply calling cpufreq_notify_post_transition() with error code and this routine will take care of sending notifications in correct order. Signed-off-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 13 ++--- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 3b877d4..a7fcb84 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1815,17 +1815,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, pr_err("%s: Failed to change cpu frequency: %d\n", __func__, retval); - if (notify) { - /* -* Notify with old freq in case we failed to change -* frequency -*/ - if (retval) - freqs.new = freqs.old; - - cpufreq_notify_transition(policy, , - CPUFREQ_POSTCHANGE); - } + if (notify) + cpufreq_notify_post_transition(policy, , retval); } out: -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH V2 2/5] cpufreq: send new set of notification for transition failures
In the current code, if we fail during a frequency transition we simply send the POSTCHANGE notification with old frequency. This isn't enough. One of the core user of these notifications is the code responsible for keeping loops_per_jiffy aligned with frequency change. And mostly it is written as: if ((val == CPUFREQ_PRECHANGE freq-old freq-new) || (val == CPUFREQ_POSTCHANGE freq-old freq-new)) { update-loops-per-jiffy... } So, suppose we are changing to a higher frequency and failed during transition, then following will happen: - CPUFREQ_PRECHANGE notification with freq-new freq-old - CPUFREQ_POSTCHANGE notification with freq-new == freq-old The first one will update loops_per_jiffy and second one will do nothing. Even if we send the 2nd notification by exchanging values of freq-new and old, some users of these notifications might get unstable. This can be fixed by simply calling cpufreq_notify_post_transition() with error code and this routine will take care of sending notifications in correct order. Signed-off-by: Viresh Kumar viresh.ku...@linaro.org --- drivers/cpufreq/cpufreq.c | 13 ++--- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 3b877d4..a7fcb84 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1815,17 +1815,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, pr_err(%s: Failed to change cpu frequency: %d\n, __func__, retval); - if (notify) { - /* -* Notify with old freq in case we failed to change -* frequency -*/ - if (retval) - freqs.new = freqs.old; - - cpufreq_notify_transition(policy, freqs, - CPUFREQ_POSTCHANGE); - } + if (notify) + cpufreq_notify_post_transition(policy, freqs, retval); } out: -- 1.7.12.rc2.18.g61b472e -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/