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bh=hJ+s+aSUGilw3vE4U5T63ufLI/Km+4j+05pH2H44ixY=; b=geZC2Wr2XV1aeCZlyQf5f2w51GjWsIQFS6VuClYpDq/IVeIV8BQOjTosZh0ywJ+Hch zs93UnFDxQI7l+2p0SmJHV+KliOV08T3QSBIpdSdhcUp4tIKnS+Q34yj8nsku3Hrn2hz vkVdVTtQQoP0AcSR8fzd3asnQvVo++wl9tZdHODKdyuUX0v8CARsGzbEeQCRLrdy4Kuo HPeOZTqBvUo/YcYhcT3qMAgVd/T9F+znf1/eBixW6C7eq4vVZBCYTJe38QSY3jYM0tI9 sp/aIqiAfXQkV80TQbVsJb3xekWx8at/QAvviUp526YmDnteVRtqHC0aZvI3nKOA7cJF hysw== X-Gm-Message-State: APjAAAVFY12gbHksTn1fAOY/Oy8XlTQvKYYrEk/px0CJGZSQjUmWon8f 5bXtyfLZbGQpxu7cRd6Tpf36/3zXpX9I6gI1K8kl3w== X-Google-Smtp-Source: APXvYqwK11aJwdy5HT6X1lC98UpcR6oEhexjUqUz5E/8oxietWEsQu3UIm8cEYuFF1ID7r045vF61qsKKm9e4RvKx98= X-Received: by 2002:a92:1d51:: with SMTP id d78mr27048415ild.166.1573407464307; Sun, 10 Nov 2019 09:37:44 -0800 (PST) MIME-Version: 1.0 References: <20191106091335.GA16729@onstation.org> <20191107111019.GA24028@onstation.org> <20191110135321.GA6728@onstation.org> In-Reply-To: <20191110135321.GA6728@onstation.org> From: Jeffrey Hugo Date: Sun, 10 Nov 2019 10:37:33 -0700 Message-ID: Subject: Re: [Freedreno] drm/msm: 'pp done time out' errors after async commit changes To: Brian Masney Cc: Rob Clark , Rob Clark , freedreno , Linux Kernel Mailing List , dri-devel , linux-arm-msm , Sean Paul Content-Type: text/plain; charset="UTF-8" Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Sun, Nov 10, 2019 at 6:53 AM Brian Masney wrote: > > On Fri, Nov 08, 2019 at 07:56:25AM -0700, Jeffrey Hugo wrote: > > On Thu, Nov 7, 2019 at 7:03 PM Rob Clark wrote: > > > > > > On Thu, Nov 7, 2019 at 9:40 AM Jeffrey Hugo wrote: > > > > > > > > On Thu, Nov 7, 2019 at 9:17 AM Rob Clark wrote: > > > > > > > > > > On Thu, Nov 7, 2019 at 3:10 AM Brian Masney wrote: > > > > > > > > > > > > On Wed, Nov 06, 2019 at 08:58:59AM -0800, Rob Clark wrote: > > > > > > > On Wed, Nov 6, 2019 at 8:47 AM Jeffrey Hugo wrote: > > > > > > > > > > > > > > > > On Wed, Nov 6, 2019 at 9:30 AM Rob Clark wrote: > > > > > > > > > > > > > > > > > > On Wed, Nov 6, 2019 at 1:13 AM Brian Masney wrote: > > > > > > > > > > > > > > > > > > > > On Tue, Nov 05, 2019 at 08:23:27AM -0800, Rob Clark wrote: > > > > > > > > > > > On Tue, Nov 5, 2019 at 2:08 AM Brian Masney wrote: > > > > > > > > > > > > The 'pp done time out' errors go away if I revert the following three > > > > > > > > > > > > commits: > > > > > > > > > > > > > > > > > > > > > > > > cd6d923167b1 ("drm/msm/dpu: async commit support") > > > > > > > > > > > > d934a712c5e6 ("drm/msm: add atomic traces") > > > > > > > > > > > > 2d99ced787e3 ("drm/msm: async commit support") > > > > > > > > > > > > > > > > > > > > > > > > I reverted the first one to fix a compiler error, and the second one so > > > > > > > > > > > > that the last patch can be reverted without any merge conflicts. > > > > > > > > > > > > > > > > > > > > > > > > I see that crtc_flush() calls mdp5_ctl_commit(). I tried to use > > > > > > > > > > > > crtc_flush_all() in mdp5_flush_commit() and the contents of the frame > > > > > > > > > > > > buffer dance around the screen like its out of sync. I renamed > > > > > > > > > > > > crtc_flush_all() to mdp5_crtc_flush_all() and removed the static > > > > > > > > > > > > declaration. Here's the relevant part of what I tried: > > > > > > > > > > > > > > > > > > > > > > > > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c > > > > > > > > > > > > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c > > > > > > > > > > > > @@ -171,7 +171,15 @@ static void mdp5_prepare_commit(struct msm_kms *kms, struct drm_atomic_state *st > > > > > > > > > > > > > > > > > > > > > > > > static void mdp5_flush_commit(struct msm_kms *kms, unsigned crtc_mask) > > > > > > > > > > > > { > > > > > > > > > > > > - /* TODO */ > > > > > > > > > > > > + struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(kms)); > > > > > > > > > > > > + struct drm_crtc *crtc; > > > > > > > > > > > > + > > > > > > > > > > > > + for_each_crtc_mask(mdp5_kms->dev, crtc, crtc_mask) { > > > > > > > > > > > > + if (!crtc->state->active) > > > > > > > > > > > > + continue; > > > > > > > > > > > > + > > > > > > > > > > > > + mdp5_crtc_flush_all(crtc); > > > > > > > > > > > > + } > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > Any tips would be appreciated. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I think this is along the lines of what we need to enable async commit > > > > > > > > > > > for mdp5 (but also removing the flush from the atomic-commit path).. > > > > > > > > > > > the principle behind the async commit is to do all the atomic state > > > > > > > > > > > commit normally, but defer writing the flush bits. This way, if you > > > > > > > > > > > get another async update before the next vblank, you just apply it > > > > > > > > > > > immediately instead of waiting for vblank. > > > > > > > > > > > > > > > > > > > > > > But I guess you are on a command mode panel, if I remember? Which is > > > > > > > > > > > a case I didn't have a way to test. And I'm not entirely about how > > > > > > > > > > > kms_funcs->vsync_time() should be implemented for cmd mode panels. > > > > > > > > > > > > > > > > > > > > Yes, this is a command-mode panel and there's no hardware frame counter > > > > > > > > > > available. The key to getting the display working on this phone was this > > > > > > > > > > patch: > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2bab52af6fe68c43b327a57e5ce5fc10eefdfadf > > > > > > > > > > > > > > > > > > > > > That all said, I think we should first fix what is broken, before > > > > > > > > > > > worrying about extending async commit support to mdp5.. which > > > > > > > > > > > shouldn't hit the async==true path, due to not implementing > > > > > > > > > > > kms_funcs->vsync_time(). > > > > > > > > > > > > > > > > > > > > > > What I think is going on is that, in the cmd mode case, > > > > > > > > > > > mdp5_wait_flush() (indirectly) calls mdp5_crtc_wait_for_pp_done(), > > > > > > > > > > > which waits for a pp-done irq regardless of whether there is a flush > > > > > > > > > > > in progress. Since there is no flush pending, the irq never comes. > > > > > > > > > > > But the expectation is that kms_funcs->wait_flush() returns > > > > > > > > > > > immediately if there is nothing to wait for. > > > > > > > > > > > > > > > > > > > > I don't think that's happening in this case. I added some pr_info() > > > > > > > > > > statements to request_pp_done_pending() and mdp5_crtc_pp_done_irq(). > > > > > > > > > > Here's the first two sets of messages that appear in dmesg: > > > > > > > > > > > > > > > > > > > > [ 14.018907] msm fd900000.mdss: pp done time out, lm=0 > > > > > > > > > > [ 14.018993] request_pp_done_pending: HERE > > > > > > > > > > [ 14.074208] mdp5_crtc_pp_done_irq: HERE > > > > > > > > > > [ 14.074368] Console: switching to colour frame buffer device 135x120 > > > > > > > > > > [ 14.138938] msm fd900000.mdss: pp done time out, lm=0 > > > > > > > > > > [ 14.139021] request_pp_done_pending: HERE > > > > > > > > > > [ 14.158097] mdp5_crtc_pp_done_irq: HERE > > > > > > > > > > > > > > > > > > > > The messages go on like this with the same pattern. > > > > > > > > > > > > > > > > > > > > I tried two different changes: > > > > > > > > > > > > > > > > > > > > 1) I moved the request_pp_done_pending() and corresponding if statement > > > > > > > > > > from mdp5_crtc_atomic_flush() and into mdp5_crtc_atomic_begin(). > > > > > > > > > > > > > > > > > > > > 2) I increased the timeout in wait_for_completion_timeout() by several > > > > > > > > > > increments; all the way to 5 seconds. > > > > > > > > > > > > > > > > > > increasing the timeout won't help, because the pp-done irq has already > > > > > > > > > come at the point where we wait for it.. > > > > > > > > > > > > > > > > > > maybe the easy thing is just add mdp5_crtc->needs_pp, set to true > > > > > > > > > before requesting, and false when we get the irq.. and then > > > > > > > > > mdp5_crtc_wait_for_pp_done() just returns if needs_pp==false.. > > > > > > > > > > > > > > > > On the otherhand, what about trying to make command mode panels > > > > > > > > resemble video mode panels slightly? Video mode panels have a vsync > > > > > > > > counter in hardware, which is missing from command mode - however it > > > > > > > > seems like the driver/drm framework would prefer such a counter. > > > > > > > > Would it be a reasonable idea to make a software counter, and just > > > > > > > > increment it every time the pp_done irq is triggered? > > > > > > > > > > > > > > > > I'm just thinking that we'll avoid issues long term by trying to make > > > > > > > > the code common, rather than diverging it for the two modes. > > > > > > > > > > > > > > > > > > > > > > *possibly*, but I think we want to account somehow periods where > > > > > > > display is not updated. > > > > > > > > > > > > > > fwiw, it isn't that uncommon for userspace to use vblanks to "keep > > > > > > > time" (drive animations for desktop switch, window > > > > > > > maximize/unmaximize, etc).. it could be a surprise when "vblank" is > > > > > > > not periodic. > > > > > > > > > > > > What do you think about using some variation of the current value of > > > > > > jiffies in the kernel + the number of pp_done IRQs as the software > > > > > > counter for command-mode panels? > > > > > > > > > > > > > > > > jiffies is probably too coarse.. but we could use monotonic clock, I guess. > > > > > > > > > > But I suppose even a cmd mode panel has a "vblank", it is just > > > > > internal the panel. Do we get the TE interrupt at regular intervals? > > > > > AFAIU this would be tied to the panel's internal vblank. > > > > > > > > The TE interrupt was first implemented in MDP 1.7.0 (msm8996). 8974 > > > > predates that. > > > > You can get it from the WR_PTR interrupt, but you have to understand > > > > details about your panel to configure that correctly. > > > > > > oh, sad.. I kinda assumed it was a pretty common DSI irq since > > > forever.. I guess the hw is just managing the flow control to prevent > > > tearing? > > > > > > Well, anyways, I guess we could just use a free-running timer based on > > > refresh rate of the panel? > > > > That would work. One more alternative (just want to make sure we've > > evaluated all options) is to use the autorefresh feature. How I would > > put it simply, is that autorefresh turns a command mode panel into a > > video mode panel. If autorefresh is enabled, the MDP will > > automatically send a frame to the panel every time the panel invokes > > the TE signal. I'm pretty sure this will automatically trigger the > > PP_DONE irq, so essentially PP_DONE is now analogous to vsync. The > > downside is that the START trigger and autorefresh are basically > > mutually exclusive. I see the autorefresh config register in MDP 1.0, > > so it would be applicable to all platforms supported by the mdp5 > > driver. > > There's a REG_MDP5_PP_AUTOREFRESH_CONFIG() macro upstream here: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/msm/disp/mdp5/mdp5.xml.h#n1383 > > I'm not sure what to put in that register but I tried configuring it > with a 1 this way and still have the same issue. > > diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c > index eeef41fcd4e1..6b9acf68fd2c 100644 > --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c > +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c > @@ -80,6 +80,7 @@ static int pingpong_tearcheck_setup(struct drm_encoder *encoder, > mdp5_write(mdp5_kms, REG_MDP5_PP_SYNC_THRESH(pp_id), > MDP5_PP_SYNC_THRESH_START(4) | > MDP5_PP_SYNC_THRESH_CONTINUE(4)); > + mdp5_write(mdp5_kms, REG_MDP5_PP_AUTOREFRESH_CONFIG(pp_id), 1); > > return 0; > } bit 31 is the enable bit (set that to 1), bits 15:0 are the frame_count (how many te events before the MDP sends a frame, I'd recommend set to 1). Then after its programmed, you'll have to flush the config, and probably use a _START to make sure the flush takes effect.