Hello, I've been working on a series which add DEV_PM_QOS support to devfreq, now at v9: https://patchwork.kernel.org/cover/11171807/ Your third patch removes DEV_PM_QOS_FREQUENCY_MIN/MAX that my series depends upon. I found the email on patchwork, hopefully the in-reply-to header is OK? As far as I can tell the replacement ("frequency qos") needs constraints to be managed outside the device infrastructure and it's not obviously usable a generic mechanism for making "min_freq/max_freq" requests to a specific device. I've read a bit through your emails and it seems the problem is that you're dealing with dev_pm_qos on per-policy basis but each "struct cpufreq_policy" can cover multiple CPU devices. An alternative solution which follows dev_pm_qos would be to add notifiers for each CPU inside cpufreq_online and cpufreq_offline. This makes quite a bit of sense because each CPU is a separate "device" with a possibly distinct list of qos requests. If cpufreq needs a group of CPUs to run at the same frequency then it should deal with this by doing dev_pm_qos_read_frequency on each CPU device and picking a frequency that attempts to satisfy all constraints. Handling sysfs min/max_freq through dev_pm_qos would be of dubious value, though I guess you could register identical requests for each CPU. I'm not familiar with what you're trying to accomplish with PM_QOS other than replace the sysfs min_freq/max_freq files: What I want to do is add a driver using the interconnect driver which translates requests for "bandwidth-on-a-path" into "frequency-on-a-device". More specifically a display driver could request bandwidth to RAM and this would be translated into min frequency for NoC and the DDR controller, both of which implement scaling via devfreq: https://patchwork.kernel.org/cover/11104113/ https://patchwork.kernel.org/cover/11111865/ This is part of an effort to upstream an out-of-tree "busfreq" feature which allows device device to make "min frequency requests" through an entirely out-of-tree mechanism. It would also allow finer-grained scaling that what IMX tree currently support. If you're making cpufreq qos constrains be "per-cpufreq-policy" then it's not clear how you would handle in-kernel constraints from other subsystems. Would users have to get a pointer to struct cpufreq_policy and struct freq_constraints? That would make object lifetime a nightmare! But dev_pm_qos solves this by tying to struct device. And if you don't care about in-kernel requests then what's the purpose of involving PM QoS? The old min/max_freq sysfs implementation worked. -- Regards, Leonard
