On Tuesday, June 07, 2016 09:58:07 AM Viresh Kumar wrote: > On 06-06-16, 23:56, Rafael J. Wysocki wrote: > > Since you are adding new code, you can write it so it doesn't do > > unnecessary checks from the start. > > Hmm, I will do all that in this series only now. > > > While at it, the "if ((freq < policy->min) || (freq > policy->max))" > > checks in cpufreq_find_index_l() and cpufreq_find_index_h() don't look > > good to me, because they very well may cause those function to return > > -EINVAL even when there's a valid table and that may cause > > acpi_cpufreq_fast_switch() to do bad things. > > Hmm. So, the checks are for sure required here, otherwise we may end up > returning a frequency which we aren't allowed to. Also note that 'freq' here > isn't the target-freq, but the entry in the freq-table. > > This routine should be returning a valid freq within the ranges specified by > policy->min/max.
Which in principle may not be possible if the range doesn't include any frequency in the table, eg. min == max and between the table entries. However, the CPU has to run at *some* frequency, even if there's none in the min/max range. And if we are sure that there is at least one valid frequency between min and max, please note that target_freq has already been clamped between them, so clamping again is rather unuseful. And of course it is racy in general, which makes it even more unuseful. > Also note that these routines shall *never* return -EINVAL, otherwise it is > mostly a bug we are hitting. So make them explicitly return a valid frequency every time. > We have enough checks in place to make sure that there is at least one valid > entry in the freq-table which is >= policy->min and <= policy->max. That assuming that the driver will always do the right thing in its ->verify callback. > I will take care of rest of the comments though. Thanks. Thanks! _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
