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? 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://lists.freedesktop.org/mailman/listinfo/dri-devel
