From: Waldemar Rymarkiewicz waldemar.rymarkiewicz@gmail.com

Original commit c5c2a97b3ac7 ("PM / OPP: Update voltage in case freq == old_freq").

This commit fixes a rare but possible case when the clk rate is updated without update of the regulator voltage.

At boot up, CPUfreq checks if the system is running at the right freq. This is a sanity check in case a bootloader set clk rate that is outside of freq table present with cpufreq core. In such cases system can be unstable so better to change it to a freq that is preset in freq-table.

The CPUfreq takes next freq that is >= policy->cur and this is our target_freq that needs to be set now.

dev_pm_opp_set_rate(dev, target_freq) checks the target_freq and the old_freq (a current rate). If these are equal it returns early. If not, it searches for OPP (old_opp) that fits best to old_freq (not listed in the table) and updates old_freq (!).

Here, we can end up with old_freq = old_opp.rate = target_freq, which is not handled in _generic_set_opp_regulator(). It's supposed to update voltage only when freq > old_freq || freq > old_freq.

if (freq > old_freq) { ret = _set_opp_voltage(dev, reg, new_supply); [...] if (freq < old_freq) { ret = _set_opp_voltage(dev, reg, new_supply); if (ret)

It results in, no voltage update while clk rate is updated.

Example: freq-table = { 1000MHz 1.15V 666MHZ 1.10V 333MHz 1.05V } boot-up-freq = 800MHz # not listed in freq-table freq = target_freq = 1GHz old_freq = 800Mhz old_opp = _find_freq_ceil(opp_table, &old_freq); #(old_freq is modified!) old_freq = 1GHz

Fixes: 6a0712f6f199 ("PM / OPP: Add dev_pm_opp_set_rate()") Cc: 4.6+ stable@vger.kernel.org # v4.6+ Signed-off-by: Waldemar Rymarkiewicz waldemar.rymarkiewicz@gmail.com Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- Sending it for stable kernels from 4.6 until 4.9.

drivers/base/power/opp/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c index 4c7c6da7a989..0580cbe5bd1c 100644 --- a/drivers/base/power/opp/core.c +++ b/drivers/base/power/opp/core.c @@ -642,7 +642,7 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq) rcu_read_unlock();

/* Scaling up? Scale voltage before frequency */ - if (freq > old_freq) { + if (freq >= old_freq) { ret = _set_opp_voltage(dev, reg, u_volt, u_volt_min, u_volt_max); if (ret)