On Wed, May 29, 2019 at 01:58:16PM -0600, Jeffrey Hugo wrote: > On 5/29/2019 1:30 PM, Brian Masney wrote: > > On Wed, May 29, 2019 at 08:41:31AM -0600, Jeffrey Hugo wrote: > > > On Wed, May 29, 2019 at 4:28 AM Brian Masney <masneyb@xxxxxxxxxxxxx> wrote: > > > > > > > > On Tue, May 28, 2019 at 08:53:49PM -0600, Jeffrey Hugo wrote: > > > > > On Tue, May 28, 2019 at 8:46 PM Brian Masney <masneyb@xxxxxxxxxxxxx> wrote: > > > > > > > > > > > > On Tue, May 28, 2019 at 07:42:19PM -0600, Jeffrey Hugo wrote: > > > > > > > > > Do you know if the nexus 5 has a video or command mode panel? There > > > > > > > > > is some glitchyness with vblanks and command mode panels. > > > > > > > > > > > > > > > > Its in command mode. I know this because I see two 'pp done time out' > > > > > > > > messages, even on 4.17. Based on my understanding, the ping pong code is > > > > > > > > only applicable for command mode panels. > > > > > > > > > > > > > > Actually, the ping pong element exists in both modes, but 'pp done > > > > > > > time out' is a good indicator that it is command mode. > > > > > > > > > > > > > > Are you also seeing vblank timeouts? > > > > > > > > > > > > Yes, here's a snippet of the first one. > > > > > > > > > > > > [ 2.556014] WARNING: CPU: 0 PID: 5 at drivers/gpu/drm/drm_atomic_helper.c:1429 drm_atomic_helper_wait_for_vblanks.part.1+0x288/0x290 > > > > > > [ 2.556020] [CRTC:49:crtc-0] vblank wait timed out > > > > > > [ 2.556023] Modules linked in: > > > > > > [ 2.556034] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.2.0-rc1-00178-g72c3c1fd5f86-dirty #426 > > > > > > [ 2.556038] Hardware name: Generic DT based system > > > > > > [ 2.556056] Workqueue: events deferred_probe_work_func > > > > > > ... > > > > > > > > > > > > > Do you have busybox? > > > > > > > > > > > > > > Can you run - > > > > > > > sudo busybox devmem 0xFD900614 > > > > > > > sudo busybox devmem 0xFD900714 > > > > > > > sudo busybox devmem 0xFD900814 > > > > > > > sudo busybox devmem 0xFD900914 > > > > > > > sudo busybox devmem 0xFD900A14 > > > > > > > > > > > > # busybox devmem 0xFD900614 > > > > > > 0x00020020 > > > > > > > > > > Ok, so CTL_0 path, command mode, ping pong 0, with the output going to DSI 1. > > > > > > > > > > Next one please: > > > > > > > > > > busybox devmem 0xFD912D30 > > > > > > > > It's 0x00000000 on mainline and 4.17. I used the following script to > > > > dump the entire mdp5 memory region and attached the dump from 4.17 and > > > > 5.2rc1. > > > > > > > > > > ok, 0 means autorefresh is not on. Which is fine. My next guess > > > would be the vblank code checking the hardware vblank counter, which > > > doesn't exist. > > > In video mode, there is a frame counter which increments, which can be > > > used as the vblank counter. Unfortunately, that hardware isn't active > > > in command mode, and there isn't an equivalent. > > > > > > So, the vblank code is going to read the register, and look for an > > > update, which will never happen, thus it will timeout. There is a > > > backup path which uses timestamps (no hardware), which you can > > > activate with a quick hack - make max_vblank_count = 0 at the > > > following line > > > https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c#L753 > > > > That fixed the issue! > > Awesome. I'm glad it was something simple. > > > > > I previously observed that mdp5_get_vblank_counter, specifically > > mdp5_encoder_get_framecount, would always return 0. > > > > What's the best way to fix this in mainline? Set that to zero if any > > of the interface modes is MDP5_INTF_DSI_MODE_COMMAND? > > > > Short version, yes. Long version: > > I still have that hack in my tree and haven't come back to formulating > a proper fix yet. Feel free to run with it. > > Thinking about it briefly, we could do two things. We could fake a > hardware counter by just increment an int every time the vblank irq is > processed, but that seems clunky. Otherwise, we could force a > fallback onto the timestamp solution, which seems less invasive. > > In theory, we could service multiple displays, with different > properties (ie a combination of command and video mode). The hack > then, is not good, because it would break video mode (at-least we > wouldn't be using the register when we could). It would be great if > the use of the hardware register could be done per display. > > Luckily, it looks like someone just made that possible - > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/drm_vblank.c?h=v5.2-rc2&id=ed20151a7699bb2c77eba3610199789a126940c4 I'll work on this for the msm driver. Thanks for the info! Brian
