Neil, On Thu, Feb 15, 2024 at 8:53 AM Neil Armstrong <neil.armstrong@xxxxxxxxxx> wrote: > > Hi Doug, > > On 15/02/2024 16:08, Doug Anderson wrote: > > Hi, > > > > On Thu, Feb 15, 2024 at 2:24 AM Jani Nikula <jani.nikula@xxxxxxxxx> wrote: > >> > >> On Wed, 14 Feb 2024, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > >>> Hi, > >>> > >>> On Tue, Feb 13, 2024 at 10:25 PM Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote: > >>>> > >>>> On Wed, Feb 14, 2024 at 2:23 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote: > >>>>> > >>>>> If an eDP panel is not powered on then any attempts to talk to it over > >>>>> the DP AUX channel will timeout. Unfortunately these attempts may be > >>>>> quite slow. Userspace can initiate these attempts either via a > >>>>> /dev/drm_dp_auxN device or via the created i2c device. > >>>>> > >>>>> Making the DP AUX drivers timeout faster is a difficult proposition. > >>>>> In theory we could just poll the panel's HPD line in the AUX transfer > >>>>> function and immediately return an error there. However, this is > >>>>> easier said than done. For one thing, there's no hard requirement to > >>>>> hook the HPD line up for eDP panels and it's OK to just delay a fixed > >>>>> amount. For another thing, the HPD line may not be fast to probe. On > >>>>> parade-ps8640 we need to wait for the bridge chip's firmware to boot > >>>>> before we can get the HPD line and this is a slow process. > >>>>> > >>>>> The fact that the transfers are taking so long to timeout is causing > >>>>> real problems. The open source fwupd daemon sometimes scans DP busses > >>>>> looking for devices whose firmware need updating. If it happens to > >>>>> scan while a panel is turned off this scan can take a long time. The > >>>>> fwupd daemon could try to be smarter and only scan when eDP panels are > >>>>> turned on, but we can also improve the behavior in the kernel. > >>>>> > >>>>> Let's let eDP panels drivers specify that a panel is turned off and > >>>>> then modify the common AUX transfer code not to attempt a transfer in > >>>>> this case. > >>>>> > >>>>> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > >>>>> --- > >>>> > >>>> Reviewed-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> > >>> > >>> Thanks for the review! > >>> > >>> Given that this touches core DRM code and that I never got > >>> confirmation that Jani's concerns were addressed with my previous > >>> response, I'm still going to wait a little while before applying. I'm > >>> on vacation for most of next week, but if there are no further replies > >>> between now and then I'll plan to apply this to "drm-misc-next" the > >>> week of Feb 26th. If someone else wants to apply this before I do then > >>> I certainly won't object. Jani: if you feel this needs more discussion > >>> or otherwise object to this patch landing then please yell. Likewise > >>> if anyone else in the community wants to throw in their opinion, feel > >>> free. > >> > >> Sorry for dropping the ball after my initial response. I simply have not > >> had the time to look into this. > >> > >> It would be great to get, say, drm-misc maintainer ack on this before > >> merging. It's not fair for me to stall this any longer, I'll trust their > >> judgement. > >> > >> Reasonable? > > > > I'd be more than happy for one of the drm-misc maintainers to Ack. > > I'll move Maxime, Thomas, and Maarten to the "To:" line to see if that > > helps get through their filters. > > I'll like some test reports to be sure it doesn't break anything, > then I'll be happy to give my ack ! Are you looking for any more test reports at this point? Eizan did some testing and provided a tag, though this was also on ChromeOS. Steev also tested on two non-ChromeOS environments and provided his tag. It's also been another two weeks of this being rolled out to some Chromebook users and I haven't heard any reports of problems. If somehow something was missed, I'm happy to follow-up and provide additional fixes if some report comes in later. Thanks! -Doug
