On Mon, Jul 02, 2018 at 02:19:47PM +0530, Viresh Kumar wrote: > From: Waldemar Rymarkiewicz <[email protected]> > > 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+ <[email protected]> # v4.6+ > Signed-off-by: Waldemar Rymarkiewicz <[email protected]> > Signed-off-by: Viresh Kumar <[email protected]> > --- > Sending it for stable kernels from 4.6 until 4.9.
Always give me a hint as to what the original commit is, otherwise I have to go dig for it :( greg k-h
