Hi Sylwester, On 11/3/20 7:12 PM, Sylwester Nawrocki wrote: > Hi Chanwoo, Georgi > > On 03.11.2020 09:53, Chanwoo Choi wrote: >> On 11/3/20 5:29 PM, Georgi Djakov wrote: >>> On 11/3/20 09:54, Chanwoo Choi wrote: > >>>> When I tested this patchset on Odroid-U3, >>>> After setting 0 bps by interconnect[1][2], >>>> the frequency of devfreq devs sustain the high frequency >>>> according to the pm qos request. >>>> >>>> So, I try to find the cause of this situation. >>>> In result, it seems that interconnect exynos driver >>>> updates the pm qos request to devfreq device >>>> during the kernel booting. Do you know why the exynos >>>> interconnect driver request the pm qos during probe >>>> without the mixer request? >>> >>> That's probably because of the sync_state support, that was introduced >>> recently. The icc_sync_state callback needs to be added to the driver >>> (i just left a comment on that patch), and then check again if it works. >>> >>> The idea of the sync_state is that there could be multiple users of a >>> path and we must wait for all consumers to tell their bandwidth needs. >>> Otherwise the first consumer may lower the bandwidth or disable a path >>> needed for another consumer (driver), which has not probed yet. So we >>> maintain a floor bandwidth until everyone has probed. By default the floor >>> bandwidth is INT_MAX, but can be overridden by implementing the get_bw() >>> callback. > > Thanks for detailed explanation Georgi. > >> Thanks for guide. I tested it with your comment of patch2. >> It is well working without problem as I mentioned previously. >> >> I caught the reset operation of PM QoS requested from interconnect >> on kernel log. In result, after completed the kernel booting, >> there is no pm qos request if hdmi cable is not connected. > > Thanks for the bug report Chanwoo, it's related to the sync_state > feature as you guys already figured out. I had to reorder some code > in the interconnect driver probe() to avoid some issues, > i.e. to register PM QoS request before icc_node_add() call but > I forgot to check initial state of the bus frequencies. > > I thought the get_bw implementation might be needed but the default > behaviour seems fine, the PM QoS derived bus frequencies will be > clamped in the devfreq to valid OPP values. > > Chanwoo, in order to set the bandwidth to 0 we could also just blank > the display. Below are some of the commands I use for testing. > > # blank display (disable the mixer entirely) > echo 4 > /sys/devices/platform/exynos-drm/graphics/fb0/blank > > # unblank display > echo 0 > /sys/devices/platform/exynos-drm/graphics/fb0/blank > > # modetest with 2 planes (higher bandwidth test) > ./modetest -s 47:1920x1080 -P 45:1920x1080 -v > Thanks for the test guide. -- Best Regards, Chanwoo Choi Samsung Electronics
