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. 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
