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.b...@linux.vnet.ibm.com>
---
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) {
+ 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;
}
--
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