From: email@example.com To: Stephen Boyd <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v4 1/2] drm/msm/dp: handle irq_hpd with sink_count = 0 correctly Date: Thu, 20 May 2021 13:36:35 -0700 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <CAE-0n52rBrjy-=dpqK+dae2GNk1rAaQnKqCjzdqiAoS13gHpSQ@mail.gmail.com> On 2021-05-20 12:28, Stephen Boyd wrote: > Quoting email@example.com (2021-05-20 09:08:03) >> On 2021-05-19 14:06, Stephen Boyd wrote: >> > Quoting firstname.lastname@example.org (2021-05-19 09:01:02) >> >> On 2021-05-18 14:42, Stephen Boyd wrote: >> >> > Quoting Kuogee Hsieh (2021-05-14 10:35:13) >> >> >> irq_hpd interrupt should be handled after dongle plugged in and >> >> >> before dongle unplugged. Hence irq_hpd interrupt is enabled at >> >> >> the end of the plugin handle and disabled at the beginning of >> >> >> unplugged handle. Current irq_hpd with sink_count = 0 is wrongly >> >> >> handled same as the dongle unplugged which tears down the mainlink >> >> >> and disables the phy. This patch fixes this problem by only tearing >> >> >> down the mainlink but keeping phy enabled at irq_hpd with >> >> >> sink_count = 0 handle so that next irq_hpd with sink_count =1 can be >> >> >> handled by setup mainlink only. >> >> >> >> >> >> Changes in v2: >> >> >> -- add ctrl->phy_Power_count >> >> >> >> >> >> Changes in v3: >> >> >> -- del ctrl->phy_Power_count >> >> >> -- add phy_power_off to dp_ctrl_off_link_stream() >> >> >> >> >> >> Changes in v4: >> >> >> -- return immediately if clock disable failed at >> >> >> dp_ctrl_off_link_stream() >> >> >> >> >> >> Signed-off-by: Kuogee Hsieh <email@example.com> >> >> > >> >> > I think we want some Fixes tag. Not sure what it would be though. >> >> > >> >> > I also noticed that if I plug and unplug the HDMI cable from my apple >> >> > dongle that I see this error message >> >> > >> >> > [drm:dp_display_usbpd_attention_cb] *ERROR* Disconnected, no >> >> > DP_LINK_STATUS_UPDATED >> >> >> >> > *ERROR* Disconnected, no DP_LINK_STATUS_UPDATED <== this is caused by >> >> > dongle generate the second >> >> irq_hpd with sink_count = 0 after first first irq_hpd with sink_count >> >> = >> >> 0. The fix is you have >> >> set dongle to D3 (power off) state after first irq_pd with sink_count >> >> =display_disable >> >> 0 handled. >> >> I have a patch fix this problem. I will merge and re submit for >> >> review. >> > >> > That's good. I still don't understand how the kthread can't race with >> > irq_hpd and hpd going low though. Userspace will have to disable >> > thectrl_off_link_stream()). >> > display and that could happen far later than the time that the hpd low >> > interrupt fires and is processed. Can't hpd go high during that time >> > and >> > then blip before userspace notices and disables the display? >> > >> > Put another way, putting the dongle into D3 state may make the race >> > window smaller, but it's not fixing the root cause of the problem which >> > is that the kthread is running later and userspace is involved in the >> > state of the dongle while irqs are firing. The three different contexts >> > have to coordinate work, so it feels like a better approach would be to >> > shut off the irq_hpd interrupt once hpd goes low for an unplug in >> > hardirq context so that we don't have to consider the cable state or >> > userspace changing the state after we notify it. >> >> There is no race condition here. >> The interrupts are converted into event and stored at event q. >> event thread service event sequentially and make sure transaction had >> been completed before service next event. >> The first irq_hpd with sink_count = 0 is handled and this transaction >> will not completed until user space frame work turn off display >> (msm_dp_display_disable()). >> After that, the second irq_hpd with sink_count will be service which >> found that display is off so it spill out DP_LINK_STATUS_UPDATED >> warning >> message and do nothing. >> >> Put dongle to D3 state so that it will not issue the unnecessary >> second >> irq_hpd with sink_count = 0. this will prevent the annoy but unharmful >> DP_LINK_STATUS_UPDATED warning message. >> Again, we can not disable hpd interrupt since dongle still attached >> and >> hdmi cable can be plugged in at any instant. >> > > Right I'm not suggesting to disable hpd interrupt, just the hpd_irq > interrupt once an unplug irq comes in, and do that in hardirq context. > Also, I'm suggesting that we consider unplug as a higher priority if > the > hard irq handler is delayed for some reason and both an unplug irq and > an hpd irq are pending in the hardware when the hard irq handler is > running. Putting the dongle into D3 state won't fix these problems. [drm:dp_display_usbpd_attention_cb] *ERROR* Disconnected, no DP_LINK_STATUS_UPDATED <== you can see this warning message by just unplugged hdmi cable out of dongle (dongle still attached to DUT).
prev parent reply other threads:[~2021-05-20 20:36 UTC|newest] Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-14 17:35 Kuogee Hsieh 2021-05-18 21:42 ` Stephen Boyd 2021-05-19 16:01 ` khsieh 2021-05-19 21:06 ` Stephen Boyd 2021-05-20 16:08 ` khsieh 2021-05-20 19:28 ` Stephen Boyd 2021-05-20 20:05 ` khsieh 2021-05-20 21:28 ` Stephen Boyd 2021-05-20 22:39 ` khsieh 2021-05-21 5:00 ` Stephen Boyd 2021-05-21 15:21 ` khsieh 2021-05-21 19:18 ` Stephen Boyd 2021-05-21 19:45 ` khsieh 2021-05-21 20:54 ` Stephen Boyd 2021-05-20 20:36 ` khsieh [this message]
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