On Thu, Feb 4, 2021 at 5:28 PM Andrzej Hajda <a.hajda@xxxxxxxxxxx> wrote: > > > W dniu 04.02.2021 o 17:05, Daniel Vetter pisze: > > On Thu, Feb 04, 2021 at 11:56:32AM +0100, Michael Tretter wrote: > >> On Thu, 04 Feb 2021 11:17:49 +0100, Daniel Vetter wrote: > >>> On Wed, Feb 3, 2021 at 9:32 PM Michael Tretter <m.tretter@xxxxxxxxxxxxxx> wrote: > >>>> On Mon, 01 Feb 2021 17:33:14 +0100, Michael Tretter wrote: > >>>>> On Tue, 15 Sep 2020 21:40:40 +0200, Andrzej Hajda wrote: > >>>>>> W dniu 14.09.2020 o 23:19, Andrzej Hajda pisze: > >>>>>>> On 14.09.2020 22:01, Michael Tretter wrote: > >>>>>>>> On Mon, 14 Sep 2020 14:31:19 +0200, Marek Szyprowski wrote: > >>>>>>>>> On 14.09.2020 10:29, Marek Szyprowski wrote: > >>>>>>>>>> On 11.09.2020 15:54, Michael Tretter wrote: > >>>>>>>>>>> Make the exynos_dsi driver a full drm bridge that can be found and > >>>>>>>>>>> used > >>>>>>>>>>> from other drivers. > >>>>>>>>>>> > >>>>>>>>>>> Other drivers can only attach to the bridge, if a mipi dsi device > >>>>>>>>>>> already attached to the bridge. This allows to defer the probe of the > >>>>>>>>>>> display pipe until the downstream bridges are available, too. > >>>>>>>>>>> > >>>>>>>>>>> Signed-off-by: Michael Tretter <m.tretter@xxxxxxxxxxxxxx> > >>>>>>>>>> This one (and the whole series applied) still fails on Exynos boards: > >>>>>>>>>> > >>>>>>>>>> [drm] Exynos DRM: using 11c00000.fimd device for DMA mapping > >>>>>>>>>> operations > >>>>>>>>>> exynos-drm exynos-drm: bound 11c00000.fimd (ops fimd_component_ops) > >>>>>>>>>> OF: graph: no port node found in /soc/dsi@11c80000 > >>>>>>>>>> 8<--- cut here --- > >>>>>>>>>> Unable to handle kernel NULL pointer dereference at virtual address > >>>>>>>>>> 00000084 > >>>>>>>>>> pgd = (ptrval) > >>>>>>>>>> [00000084] *pgd=00000000 > >>>>>>>>>> Internal error: Oops: 5 [#1] PREEMPT SMP ARM > >>>>>>>>>> Modules linked in: > >>>>>>>>>> CPU: 1 PID: 1 Comm: swapper/0 Not tainted > >>>>>>>>>> 5.9.0-rc4-next-20200911-00010-g417dc70d70ec #1608 > >>>>>>>>>> Hardware name: Samsung Exynos (Flattened Device Tree) > >>>>>>>>>> PC is at drm_bridge_attach+0x18/0x164 > >>>>>>>>>> LR is at exynos_dsi_bind+0x88/0xa8 > >>>>>>>>>> pc : [<c0628c08>] lr : [<c064d560>] psr: 20000013 > >>>>>>>>>> sp : ef0dfca8 ip : 00000002 fp : c13190e0 > >>>>>>>>>> r10: 00000000 r9 : ee46d580 r8 : c13190e0 > >>>>>>>>>> r7 : ee438800 r6 : 00000018 r5 : ef253810 r4 : ef39e840 > >>>>>>>>>> r3 : 00000000 r2 : 00000018 r1 : ef39e888 r0 : ef39e840 > >>>>>>>>>> Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > >>>>>>>>>> Control: 10c5387d Table: 4000404a DAC: 00000051 > >>>>>>>>>> Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) > >>>>>>>>>> Stack: (0xef0dfca8 to 0xef0e0000) > >>>>>>>>>> ... > >>>>>>>>>> [<c0628c08>] (drm_bridge_attach) from [<c064d560>] > >>>>>>>>>> (exynos_dsi_bind+0x88/0xa8) > >>>>>>>>>> [<c064d560>] (exynos_dsi_bind) from [<c066a800>] > >>>>>>>>>> (component_bind_all+0xfc/0x290) > >>>>>>>>>> [<c066a800>] (component_bind_all) from [<c0649dc0>] > >>>>>>>>>> (exynos_drm_bind+0xe4/0x19c) > >>>>>>>>>> [<c0649dc0>] (exynos_drm_bind) from [<c066ad74>] > >>>>>>>>>> (try_to_bring_up_master+0x1e4/0x2c4) > >>>>>>>>>> [<c066ad74>] (try_to_bring_up_master) from [<c066b2b4>] > >>>>>>>>>> (component_master_add_with_match+0xd4/0x108) > >>>>>>>>>> [<c066b2b4>] (component_master_add_with_match) from [<c0649ae8>] > >>>>>>>>>> (exynos_drm_platform_probe+0xe4/0x110) > >>>>>>>>>> [<c0649ae8>] (exynos_drm_platform_probe) from [<c0674e6c>] > >>>>>>>>>> (platform_drv_probe+0x6c/0xa4) > >>>>>>>>>> [<c0674e6c>] (platform_drv_probe) from [<c067242c>] > >>>>>>>>>> (really_probe+0x200/0x4fc) > >>>>>>>>>> [<c067242c>] (really_probe) from [<c06728f0>] > >>>>>>>>>> (driver_probe_device+0x78/0x1fc) > >>>>>>>>>> [<c06728f0>] (driver_probe_device) from [<c0672cd8>] > >>>>>>>>>> (device_driver_attach+0x58/0x60) > >>>>>>>>>> [<c0672cd8>] (device_driver_attach) from [<c0672dbc>] > >>>>>>>>>> (__driver_attach+0xdc/0x174) > >>>>>>>>>> [<c0672dbc>] (__driver_attach) from [<c06701b4>] > >>>>>>>>>> (bus_for_each_dev+0x68/0xb4) > >>>>>>>>>> [<c06701b4>] (bus_for_each_dev) from [<c06714e8>] > >>>>>>>>>> (bus_add_driver+0x158/0x214) > >>>>>>>>>> [<c06714e8>] (bus_add_driver) from [<c0673c1c>] > >>>>>>>>>> (driver_register+0x78/0x110) > >>>>>>>>>> [<c0673c1c>] (driver_register) from [<c0649ca8>] > >>>>>>>>>> (exynos_drm_init+0xe4/0x118) > >>>>>>>>>> [<c0649ca8>] (exynos_drm_init) from [<c0102484>] > >>>>>>>>>> (do_one_initcall+0x8c/0x42c) > >>>>>>>>>> [<c0102484>] (do_one_initcall) from [<c11011c0>] > >>>>>>>>>> (kernel_init_freeable+0x190/0x1dc) > >>>>>>>>>> [<c11011c0>] (kernel_init_freeable) from [<c0af7880>] > >>>>>>>>>> (kernel_init+0x8/0x118) > >>>>>>>>>> [<c0af7880>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20) > >>>>>>>>>> Exception stack(0xef0dffb0 to 0xef0dfff8) > >>>>>>>>>> ... > >>>>>>>>>> ---[ end trace ee27f313f9ed9da1 ]--- > >>>>>>>>>> > >>>>>>>>>> # arm-linux-gnueabi-addr2line -e vmlinux c0628c08 > >>>>>>>>>> drivers/gpu/drm/drm_bridge.c:184 (discriminator 1) > >>>>>>>>>> > >>>>>>>>>> I will try to debug it a bit more today. > >>>>>>>>> The above crash has been caused by lack of in_bridge initialization to > >>>>>>>>> NULL in exynos_dsi_bind() in this patch. However, fixing it reveals > >>>>>>>>> another issue: > >>>>>>>>> > >>>>>>>>> [drm] Exynos DRM: using 11c00000.fimd device for DMA mapping operations > >>>>>>>>> exynos-drm exynos-drm: bound 11c00000.fimd (ops fimd_component_ops) > >>>>>>>>> OF: graph: no port node found in /soc/dsi@11c80000 > >>>>>>>>> 8<--- cut here --- > >>>>>>>>> Unable to handle kernel NULL pointer dereference at virtual address > >>>>>>>>> 00000280 > >>>>>>>>> pgd = (ptrval) > >>>>>>>>> [00000280] *pgd=00000000 > >>>>>>>>> Internal error: Oops: 5 [#1] PREEMPT SMP ARM > >>>>>>>>> Modules linked in: > >>>>>>>>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted > >>>>>>>>> 5.9.0-rc4-next-20200911-00010-g417dc70d70ec-dirty #1613 > >>>>>>>>> Hardware name: Samsung Exynos (Flattened Device Tree) > >>>>>>>>> PC is at __mutex_lock+0x54/0xb18 > >>>>>>>>> LR is at lock_is_held_type+0x80/0x138 > >>>>>>>>> pc : [<c0afc920>] lr : [<c0af63e8>] psr: 60000013 > >>>>>>>>> sp : ef0dfd30 ip : 33937b74 fp : c13193c8 > >>>>>>>>> r10: c1208eec r9 : 00000000 r8 : ee45f808 > >>>>>>>>> r7 : c19561a4 r6 : 00000000 r5 : 00000000 r4 : 0000024c > >>>>>>>>> r3 : 00000000 r2 : 00204140 r1 : c124f13c r0 : 00000000 > >>>>>>>>> Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > >>>>>>>>> Control: 10c5387d Table: 4000404a DAC: 00000051 > >>>>>>>>> Process swapper/0 (pid: 1, stack limit = 0x(ptrval)) > >>>>>>>>> Stack: (0xef0dfd30 to 0xef0e0000) > >>>>>>>>> ... > >>>>>>>>> [<c0afc920>] (__mutex_lock) from [<c0afd400>] > >>>>>>>>> (mutex_lock_nested+0x1c/0x24) > >>>>>>>>> [<c0afd400>] (mutex_lock_nested) from [<c064d4b8>] > >>>>>>>>> (__exynos_dsi_host_attach+0x20/0x6c) > >>>>>>>>> [<c064d4b8>] (__exynos_dsi_host_attach) from [<c064d914>] > >>>>>>>>> (exynos_dsi_host_attach+0x70/0x194) > >>>>>>>>> [<c064d914>] (exynos_dsi_host_attach) from [<c0656b64>] > >>>>>>>>> (s6e8aa0_probe+0x1b0/0x218) > >>>>>>>>> [<c0656b64>] (s6e8aa0_probe) from [<c0672530>] > >>>>>>>>> (really_probe+0x200/0x4fc) > >>>>>>>>> [<c0672530>] (really_probe) from [<c06729f4>] > >>>>>>>>> (driver_probe_device+0x78/0x1fc) > >>>>>>>>> [<c06729f4>] (driver_probe_device) from [<c0672ddc>] > >>>>>>>>> (device_driver_attach+0x58/0x60) > >>>>>>>>> [<c0672ddc>] (device_driver_attach) from [<c0672ec0>] > >>>>>>>>> (__driver_attach+0xdc/0x174) > >>>>>>>>> [<c0672ec0>] (__driver_attach) from [<c06702b8>] > >>>>>>>>> (bus_for_each_dev+0x68/0xb4) > >>>>>>>>> [<c06702b8>] (bus_for_each_dev) from [<c06715ec>] > >>>>>>>>> (bus_add_driver+0x158/0x214) > >>>>>>>>> [<c06715ec>] (bus_add_driver) from [<c0673d20>] > >>>>>>>>> (driver_register+0x78/0x110) > >>>>>>>>> [<c0673d20>] (driver_register) from [<c0102484>] > >>>>>>>>> (do_one_initcall+0x8c/0x42c) > >>>>>>>>> [<c0102484>] (do_one_initcall) from [<c11011c0>] > >>>>>>>>> (kernel_init_freeable+0x190/0x1dc) > >>>>>>>>> [<c11011c0>] (kernel_init_freeable) from [<c0af7988>] > >>>>>>>>> (kernel_init+0x8/0x118) > >>>>>>>>> [<c0af7988>] (kernel_init) from [<c0100114>] (ret_from_fork+0x14/0x20) > >>>>>>>>> Exception stack(0xef0dffb0 to 0xef0dfff8) > >>>>>>>>> ... > >>>>>>>>> ---[ end trace c06e996ec2e8234d ]--- > >>>>>>>>> > >>>>>>>>> This means that dsi->encoder.dev is not initialized in > >>>>>>>>> __exynos_dsi_host_attach(). > >>>>>>>>> > >>>>>>>>> This happens, because drm_bridge_attach() in exynos_dsi_bind() returned > >>>>>>>>> earlier -517 (deferred probe), what causes cleanup of encoder and > >>>>>>>>> release of all drm resources. > >>>>>>>>> > >>>>>>>>> Then however, the panel tries to register itself and > >>>>>>>>> exynos_dsi_host_attach() tries to access the released encoder (which is > >>>>>>>>> zeroed in drm_encoder_release) and rest of resources, what causes > >>>>>>>>> failure. > >>>>>>>>> > >>>>>>>>> It looks that something is missing. Maybe mipi host has to be > >>>>>>>>> registered > >>>>>>>>> later, when bridge is ready? I have no idea how it is handled before > >>>>>>>>> this patch. Andrzej, could you comment it a bit? > >>>>>>>> I intentionally changed the order, because if another bridge follows > >>>>>>>> in the > >>>>>>>> pipeline, the probe of the drm driver has to be deferred until some > >>>>>>>> bridge > >>>>>>>> provides a connector. The next bridge registers itself via the > >>>>>>>> host_attach > >>>>>>>> function and the deferral is ensured via the bind for the bind/unbind > >>>>>>>> API or > >>>>>>>> the bridge_attach function otherwise. > >>>>>>>> > >>>>>>>> On the other hand, the bridge does not have an encoder until the mipi > >>>>>>>> device > >>>>>>>> has been attached. > >>>>>>>> > >>>>>>>> As a solution, the exynos dsi driver must initialize the encoder in > >>>>>>>> exynos_dsi_probe instead of in exynos_dsi_bind and access the encoder > >>>>>>>> via > >>>>>>>> exynos_dsi instead of the bridge. > >>>>>>>> > >>>>>>>> Can you try to move everything except samsung_dsim_bind from > >>>>>>>> exynos_dsi_bind > >>>>>>>> to exynos_dsi_probe (respectively for unbind) and report if it fixes the > >>>>>>>> crash. > >>>>>>> > >>>>>>> The original behaviour is that encoder (exynos_dsi) is registered > >>>>>>> regardless of sink presence (initially panel, later also bridge) - it > >>>>>>> avoids multiple issues with deferred probe, device driver bind/unbind > >>>>>>> and module load/unload. Appearance or disappearance of sink is > >>>>>>> reported to host nicely via DSI attach/detach callbacks - and it is > >>>>>>> reflected in drm world as change state of the connector. > >>>>>>> > >>>>>>> Registering DSI host in bind and unregistering in unbind assures that > >>>>>>> if mipi_dsi device is attached/detached the drm device is always > >>>>>>> present - it makes device/driver binding race free and allows to avoid > >>>>>>> additional locking. > >>>>>>> > >>>>>>> Moving DSI host registration to probe changes everything, for sure it > >>>>>>> breaks the nice feature of DSI attach/detach callbacks and apparently > >>>>>>> can cause different issues depending on device bind order. > >>>>>>> > >>>>>>> I will try to look at the patches tomorrow and maybe I can find more > >>>>>>> constructive comments :) > >>>>>> > >>>>>> As I said yesterday, exynos_dsi driver uses dsi host attach/detach > >>>>>> callbacks to control appearance/disappearance of downstream device. It > >>>>>> allows to: > >>>>>> > >>>>>> 1. Safely bind/unbind different device drivers at any time and at any > >>>>>> order, without killing exynos_drm and/or crashing system. > >>>>>> > >>>>>> 2. Avoid issues with late drm init - on some platforms exynos_drm device > >>>>>> appeared too late, due to deferred probe, and resulted in black screen > >>>>>> in userspace. > >>>>>> > >>>>>> > >>>>>> Now if we want to convert exynos_dsi to drm_bridge I see following options: > >>>>>> > >>>>>> A. Forgot about callbacks and make the exynos_drm to defer probing until > >>>>>> exynos_dsi bridge is available, probably it will cause later exynos_drm > >>>>>> appearance, thus probably black screen on some targets. So for sure it > >>>>>> will be suboptimal. Making it bridge unbind safe would be another > >>>>>> problem, but most developers do not care about it so why should we? :) > >>>>>> > >>>>>> B. Try to mimic current behaviour - exynos_dsi register bridge ASAP, > >>>>>> even if downstream devices are not yet attached, on attach/detach notify > >>>>>> drm about it via connector status change, for this dsi_host registration > >>>>>> should be performed from drm_bridge attach, I guess. > >>>>>> > >>>>>> > >>>>>> Option A is more standard, but is unsafe and causes other issues. > >>>>>> > >>>>>> Option B keeps current behaviour. > >>>>> Maybe we can have both, but I am not sure, if I am missing something: > >>>>> > >>>>> I still prefer option A for the samsung-dsim driver, because it is more > >>>>> standard, simpler and avoids issues with encoders, connectors or handling > >>>>> hotplug. > >>>>> > >>>>> The idea is to use two bridges in the exynos-dsi driver: One bridge in the > >>>>> samsung-dsim driver which implements option A and defers probing of the drm > >>>>> driver until the next bridge is attached. And a second bridge in the > >>>>> exynos_dsi that attaches to the first bridge (thus, allowing the exynos_drm > >>>>> device to appear) and implements the hotplug handling for notifying drm via > >>>>> connector status change. > >>>>> > >>>>> The driver for the i.MX8M would use the samsung-dsim bridge without an > >>>>> additional bridge. > >>>>> > >>>>> This allows the samsung-dsim driver to expose the standard behavior while the > >>>>> exynos_dsi may stick to the existing behavior for the exynos_drm driver. > >>>>> > >>>>> I hope this makes sense and does not sound too crazy. It might be difficult to > >>>>> get the probing and mipi host/device registration correct, but I will try, if > >>>>> this can work. > >>>> Adding two bridges for being able to support hotplugging adds many special > >>>> cases to the bridge driver and still requires more custom API to correctly add > >>>> the second bridge. I don't think that this a viable path to go. > >>> Just jumping in here: You cannot hotplug/hotremove anything from a > >>> drm_device after drm_dev_register has been called, except > >>> drm_connector. I didn't dig into details here so not sure whether you > >>> want to late-bind your bridge after drm_dev_register is called or not, > >>> so might just be fyi and not relevant to the discussion. > >> Thanks. AFAIC that is exactly what is currently implemented in the exynos_drm > >> driver (i.e. Option B) > >> > >> exynos_dsi_bind configures the encoder and registers a DSI host. Afterwards, > >> exynos_drm_bind (as component_master_ops) calls drm_dev_register. Later, a DSI > >> device might attach to the DSI host and call exynos_dsi_host_attach. In > >> exynos_dsi_host_attach, the driver finds the drm_bridge for the DSI device and > >> attaches this bridge to the encoder _after_ drm_dev_register has been called. > >> This is invalid behavior, right? > > Definitely not supported, I don't think we have the right locks in place > > to make sure this works. > > > > Now if your _only_ adding a drm_bridge (and not an encoder or anything > > like that), and you are adding the drm_connector correctly (like a > > hotplugged DP MST sink), then that would at least work from a uapi pov. > > Because drm_bridge isn't exposed as an uapi object. > > > > But yeah, as-is, don't :-) > > > > The solution here is a bunch of EPROBE_DEFER handling until all your > > bridges are loaded, with or without the assistance of component.c > > framework. Only then call drm_dev_register. > > -Daniel > > > I have impression we have similar conversation already. > > As you stated drm_bridge and drm_panel are not exposed to userspace so > there shouldn't be problem with them from uapi PoV. > > On the other side drm_panel or drm_bridge are not used until pipeline > enters connected state (at least they were not some time ago :) ). The > issue is that bridge exposes drm_connector, but as you stated (again :) > ) connectors can be hotplugged, so in theory it should work. Practical > tests shows that it also works, but bugs can be still there. > > Bunch of EPROBE_DEFER was very slow (as a result userspace timeouted and > decided there is no display), and does not handle unbinding/re-binding > drivers. Rebinding drivers should be fixed now, with a bunch of fixes in driver core. If not, we need to fix this more. Also, EPROBE_DEFER is how this is supposed to work. If it's too slow, we need to fix EPROBE_DEFER (there's ideas for pre-sorting that never seem to go anywhere), not paper over it with bad architecture in drivers. There's also a bit the issue that most userspace handles panels in a special way, and if they don't find the panel at first, that doesn't work. Stuff like "which is the main screen" on laptops. So yeah please fix this properly. -Daniel > > > Regards > > Andrzej > > > > > >> Michael > >> > >>> -Daniel > >>> > >>>> This leaves us with: > >>>> > >>>> Option A) Standard drm_bridge behavior, which is currently implemented, but > >>>> incompatible with the currently expected behavior of exynos_drm. > >>>> > >>>> Option B) Creating the drm device without all bridges being attached, which > >>>> would work with the exynos_drm driver, but breaks for the standard drm_bridge > >>>> behavior, especially, if the encoder/connector is created at the beginning of > >>>> the pipeline and passed downwards when the bridges are attached. > >>>> > >>>> Option C) Extracting only low level register accesses into shared code, adding > >>>> a custom interface and implementing the drm_bridge handling in the platform > >>>> specific code. > >>>> > >>>> None of the options really convinces me. > >>>> > >>>> Michael > >>>> _______________________________________________ > >>>> dri-devel mailing list > >>>> dri-devel@xxxxxxxxxxxxxxxxxxxxx > >>>> https://protect2.fireeye.com/v1/url?k=9b91fda0-c40ac4d5-9b9076ef-0cc47a31ce4e-a7f88871f6fd42d4&q=1&e=f2cfade9-8ecf-4697-88b3-69d93ed38361&u=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
