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    SubjectRe: [PATCH AUTOSEL 4.19 123/158] cpufreq: Don't skip frequency validation for has_target() drivers
    On Tue, Jul 16, 2019 at 11:21:34AM +0200, Rafael J. Wysocki wrote:
    >On 7/15/2019 4:17 PM, Sasha Levin wrote:
    >>From: Viresh Kumar <viresh.kumar@linaro.org>
    >>
    >>[ Upstream commit 9801522840cc1073f8064b4c979b7b6995c74bca ]
    >>
    >>CPUFREQ_CONST_LOOPS was introduced in a very old commit from pre-2.6
    >>kernel release by commit 6a4a93f9c0d5 ("[CPUFREQ] Fix 'out of sync'
    >>issue").
    >>
    >>Basically, that commit does two things:
    >>
    >> - It adds the frequency verification code (which is quite similar to
    >> what we have today as well).
    >>
    >> - And it sets the CPUFREQ_CONST_LOOPS flag only for setpolicy drivers,
    >> rightly so based on the code we had then. The idea was to avoid
    >> frequency validation for setpolicy drivers as the cpufreq core doesn't
    >> know what frequency the hardware is running at and so no point in
    >> doing frequency verification.
    >>
    >>The problem happened when we started to use the same CPUFREQ_CONST_LOOPS
    >>flag for constant loops-per-jiffy thing as well and many has_target()
    >>drivers started using the same flag and unknowingly skipped the
    >>verification of frequency. There is no logical reason behind skipping
    >>frequency validation because of the presence of CPUFREQ_CONST_LOOPS
    >>flag otherwise.
    >>
    >>Fix this issue by skipping frequency validation only for setpolicy
    >>drivers and always doing it for has_target() drivers irrespective of
    >>the presence or absence of CPUFREQ_CONST_LOOPS flag.
    >>
    >>cpufreq_notify_transition() is only called for has_target() type driver
    >>and not for set_policy type, and the check is simply redundant. Remove
    >>it as well.
    >>
    >>Also remove () around freq comparison statement as they aren't required
    >>and checkpatch also warns for them.
    >>
    >>Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
    >>Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    >>Signed-off-by: Sasha Levin <sashal@kernel.org>
    >>---
    >> drivers/cpufreq/cpufreq.c | 13 +++++--------
    >> 1 file changed, 5 insertions(+), 8 deletions(-)
    >>
    >>diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
    >>index d3213594d1a7..80942ec34efd 100644
    >>--- a/drivers/cpufreq/cpufreq.c
    >>+++ b/drivers/cpufreq/cpufreq.c
    >>@@ -321,12 +321,10 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy,
    >> * which is not equal to what the cpufreq core thinks is
    >> * "old frequency".
    >> */
    >>- if (!(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
    >>- if (policy->cur && (policy->cur != freqs->old)) {
    >>- pr_debug("Warning: CPU frequency is %u, cpufreq assumed %u kHz\n",
    >>- freqs->old, policy->cur);
    >>- freqs->old = policy->cur;
    >>- }
    >>+ if (policy->cur && policy->cur != freqs->old) {
    >>+ pr_debug("Warning: CPU frequency is %u, cpufreq assumed %u kHz\n",
    >>+ freqs->old, policy->cur);
    >>+ freqs->old = policy->cur;
    >> }
    >> for_each_cpu(freqs->cpu, policy->cpus) {
    >>@@ -1543,8 +1541,7 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy)
    >> if (policy->fast_switch_enabled)
    >> return ret_freq;
    >>- if (ret_freq && policy->cur &&
    >>- !(cpufreq_driver->flags & CPUFREQ_CONST_LOOPS)) {
    >>+ if (has_target() && ret_freq && policy->cur) {
    >> /* verify no discrepancy between actual and
    >> saved value exists */
    >> if (unlikely(ret_freq != policy->cur)) {
    >
    >This is not -stable material, please drop it.

    I've dropped it, thanks!

    --
    Thanks,
    Sasha

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