On 25 April 2014 13:48, Srivatsa S. Bhat
<srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote:
> During frequency transitions, the cpufreq core takes the responsibility of
> invoking cpufreq_freq_transition_begin() and cpufreq_freq_transition_end()
> for those cpufreq drivers that define the ->target_index callback but don't
> set the ASYNC_NOTIFICATION flag.
>
> The powernow-k6 cpufreq driver falls under this category, but this driver was
> invoking the _begin() and _end() APIs itself around frequency transitions,
> which led to double invocation of the _begin() API. The _begin API makes
> contending callers wait until the previous invocation is complete. Hence,
> the powernow-k6 driver ended up waiting on itself, leading to system hangs
> during boot.
>
> Fix this by removing the calls to the _begin() and _end() APIs from the
> powernow-k6 driver, since they rightly belong to the cpufreq core.
>
> (Note that during ->exit(), the powernow-k6 driver sets the frequency
> without any help from the cpufreq core. So add explicit calls to the
> _begin() and _end() APIs around that frequency transition alone, to take
> care of that special case. Also, add a missing 'break' statement there.)
>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> ---
>
> drivers/cpufreq/powernow-k6.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cpufreq/powernow-k6.c b/drivers/cpufreq/powernow-k6.c
> index 49f120e..6a4c34e 100644
> --- a/drivers/cpufreq/powernow-k6.c
> +++ b/drivers/cpufreq/powernow-k6.c
> @@ -138,22 +138,14 @@ static void powernow_k6_set_cpu_multiplier(unsigned int best_i)
> static int powernow_k6_target(struct cpufreq_policy *policy,
> unsigned int best_i)
> {
> - struct cpufreq_freqs freqs;
>
> if (clock_ratio[best_i].driver_data > max_multiplier) {
> printk(KERN_ERR PFX "invalid target frequency\n");
> return -EINVAL;
> }
>
> - freqs.old = busfreq * powernow_k6_get_cpu_multiplier();
> - freqs.new = busfreq * clock_ratio[best_i].driver_data;
> -
> - cpufreq_freq_transition_begin(policy, &freqs);
> -
> powernow_k6_set_cpu_multiplier(best_i);
>
> - cpufreq_freq_transition_end(policy, &freqs, 0);
> -
> return 0;
> }
>
> @@ -228,8 +220,18 @@ static int powernow_k6_cpu_exit(struct cpufreq_policy *policy)
> {
> unsigned int i;
> for (i = 0; i < 8; i++) {
> - if (i == max_multiplier)
> + if (i == max_multiplier) {
This wouldn't work, it has to be: (clock_ratio[i].driver_data == max_multiplier)
> + struct cpufreq_freqs freqs;
> +
> + freqs.old = policy->cur;
> + freqs.new = clock_ratio[i].frequency;
> + freqs.flags = 0;
> +
> + cpufreq_freq_transition_begin(policy, &freqs);
> powernow_k6_target(policy, i);
> + cpufreq_freq_transition_end(policy, &freqs, 0);
> + break;
> + }
> }
> return 0;
> }
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
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