On Tue, Oct 22, 2019 at 10:48 AM Russell King - ARM Linux admin <linux@xxxxxxxxxxxxxxx> wrote: > > On Tue, Oct 22, 2019 at 10:42:10AM +0200, Daniel Vetter wrote: > > On Thu, Oct 17, 2019 at 12:41:37PM +0100, Russell King - ARM Linux admin wrote: > > > On Thu, Oct 17, 2019 at 10:48:12AM +0000, Brian Starkey wrote: > > > > On Thu, Oct 17, 2019 at 10:21:03AM +0000, james qian wang (Arm Technology China) wrote: > > > > > On Thu, Oct 17, 2019 at 08:20:56AM +0000, Brian Starkey wrote: > > > > > > On Thu, Oct 17, 2019 at 03:07:59AM +0000, james qian wang (Arm Technology China) wrote: > > > > > > > On Wed, Oct 16, 2019 at 04:22:07PM +0000, Brian Starkey wrote: > > > > > > > > > > > > > > > > If James is strongly against merging this, maybe we just swap > > > > > > > > wholesale to bridge? But for me, the pragmatic approach would be this > > > > > > > > stop-gap. > > > > > > > > > > > > > > > > > > > > > > This is a good idea, and I vote +ULONG_MAX :) > > > > > > > > > > > > > > and I also checked tda998x driver, it supports bridge. so swap the > > > > > > > wholesale to brige is perfect. :) > > > > > > > > > > > > > > > > > > > Well, as Mihail wrote, it's definitely not perfect. > > > > > > > > > > > > Today, if you rmmod tda998x with the DPU driver still loaded, > > > > > > everything will be unbound gracefully. > > > > > > > > > > > > If we swap to bridge, then rmmod'ing tda998x (or any other bridge > > > > > > driver the DPU is using) with the DPU driver still loaded will result > > > > > > in a crash. > > > > > > > > > > I haven't read the bridge code, but seems this is a bug of drm_bridge, > > > > > since if the bridge is still in using by others, the rmmod should fail > > > > > > > > > > > > > Correct, but there's no fix for that today. You can also take a look > > > > at the thread linked from Mihail's cover letter. > > > > > > > > > And personally opinion, if the bridge doesn't handle the dependence. > > > > > for us: > > > > > > > > > > - add such support to bridge > > > > > > > > That would certainly be helpful. I don't know if there's consensus on > > > > how to do that. > > > > > > > > > or > > > > > - just do the insmod/rmmod in correct order. > > > > > > > > > > > So, there really are proper benefits to sticking with the component > > > > > > code for tda998x, which is why I'd like to understand why you're so > > > > > > against this patch? > > > > > > > > > > > > > > > > This change handles two different connectors in komeda internally, compare > > > > > with one interface, it increases the complexity, more risk of bug and more > > > > > cost of maintainance. > > > > > > > > > > > > > Well, it's only about how to bind the drivers - two different methods > > > > of binding, not two different connectors. I would argue that carrying > > > > our out-of-tree patches to support both platforms is a larger > > > > maintenance burden. > > > > > > > > Honestly this looks like a win-win to me. We get the superior approach > > > > when its supported, and still get to support bridges which are more > > > > common. > > > > > > > > As/when improvements are made to the bridge code we can remove the > > > > component bits and not lose anything. > > > > > > There was an idea a while back about using the device links code to > > > solve the bridge issue - but at the time the device links code wasn't > > > up to the job. I think that's been resolved now, but I haven't been > > > able to confirm it. I did propose some patches for bridge at the > > > time but they probably need updating. > > > > I think the only patches that existed where for panel, and we only > > discussed the bridge case. At least I can only find patches for panel,not > > bridge, but might be missing something. > > I had a patches, which is why I raised the problem with the core: > > 6961edfee26d bridge hacks using device links > > but it never went further than an experiment at the time because of the > problems in the core. As it was a hack, it never got posted. Seems > that kernel tree (for the cubox) is still 5.2 based, so has a lot of > patches and might need updating to a more recent base before anything > can be tested. For reference, the panel patch: https://patchwork.kernel.org/patch/10364873/ And the huge discussion around bridges, that resulted in Rafael Wyzocki fixing all the core issues: https://www.spinics.net/lists/dri-devel/msg201927.html James, do you want to look into this for bridges? Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
