Re: [PATCH 2/7] drm/dp_mst: Register AUX devices for MST ports

[Lyude Paul <lyude@redhat.com>]

On Thu, 2019-05-30 at 18:20 +0000, Li, Sun peng (Leo) wrote:
> Hey, sorry for my late response!
> 
> On 2019-05-16 5:40 p.m., Lyude Paul wrote:
> 
> > >        if (old_pdt != port->pdt && !port->input) {
> > > @@ -1220,6 +1268,8 @@ static void drm_dp_add_port(struct
> > > drm_dp_mst_branch
> > > *mstb,
> > >                        drm_connector_set_tile_property(port->connector);
> > >                }
> > >                (*mstb->mgr->cbs->register_connector)(port->connector);
> > This is wrong: we always want to setup everything in the connector first
> > before trying to register it, not after. Otherwise, things explode like
> > so:
> 
> **snip**
> 
> > [  452.424461] ------------[ cut here ]------------
> > [  452.424464] sysfs group 'power' not found for kobject 'drm_dp_aux5'
> > [  452.424471] WARNING: CPU: 3 PID: 1887 at fs/sysfs/group.c:256
> > sysfs_remove_group+0x76/0x80
> > [  452.424473] Modules linked in: vfat fat elan_i2c i915(O) intel_rapl
> > x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel iTCO_wdt kvm
> > mei_wdt irqbypass iTCO_vendor_support crct10dif_pclmul wmi_bmof
> > intel_wmi_thunderbolt crc32_pclmul i2c_algo_bit ghash_clmulni_intel
> > intel_cstate drm_kms_helper(O) intel_uncore intel_rapl_perf btusb btrtl
> > btbcm syscopyarea btintel sysfillrect sysimgblt fb_sys_fops bluetooth
> > drm(O) joydev mei_me idma64 ucsi_acpi thunderbolt ecdh_generic i2c_i801
> > intel_xhci_usb_role_switch processor_thermal_device typec_ucsi
> > intel_lpss_pci intel_soc_dts_iosf mei roles intel_lpss typec
> > intel_pch_thermal wmi thinkpad_acpi ledtrig_audio rfkill int3403_thermal
> > int340x_thermal_zone int3400_thermal acpi_thermal_rel acpi_pad video
> > pcc_cpufreq crc32c_intel nvme serio_raw uas e1000e nvme_core usb_storage
> > i2c_dev
> > [  452.424492] CPU: 3 PID: 1887 Comm: unloadgpumod Tainted:
> > G           O      5.1.0Lyude-Test+ #1
> > [  452.424494] Hardware name: LENOVO 20L8S2N800/20L8S2N800, BIOS N22ET35W
> > (1.12 ) 04/09/2018
> > [  452.424496] RIP: 0010:sysfs_remove_group+0x76/0x80
> > [  452.424498] Code: 48 89 df 5b 5d 41 5c e9 f8 bc ff ff 48 89 df e8 d0 bc
> > ff ff eb cb 49 8b 14 24 48 8b 75 00 48 c7 c7 08 a5 0c aa e8 44 00 d6 ff
> > <0f> 0b 5b 5d 41 5c c3 0f 1f 00 0f 1f 44 00 00 48 85 f6 74 31 41 54
> > [  452.424500] RSP: 0018:ffffa8bb81b5fb28 EFLAGS: 00010282
> > [  452.424501] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
> > 0000000000000006
> > [  452.424502] RDX: 0000000000000007 RSI: 0000000000000086 RDI:
> > ffff981fde2d5a00
> > [  452.424503] RBP: ffffffffa9ea12e0 R08: 0000000000000792 R09:
> > 0000000000000046
> > [  452.424504] R10: 0000000000000727 R11: ffffa8bb81b5f9d0 R12:
> > ffff981fd5f77010
> > [  452.424505] R13: ffff981fd6ebbedc R14: dead000000000200 R15:
> > dead000000000100
> > [  452.424507] FS:  00007f8cc1d8c740(0000) GS:ffff981fde2c0000(0000)
> > knlGS:0000000000000000
> > [  452.424508] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  452.424509] CR2: 000055b19d079a08 CR3: 000000043b2a0002 CR4:
> > 00000000003606e0
> > [  452.424510] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> > 0000000000000000
> > [  452.424511] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> > 0000000000000400
> > [  452.424512] Call Trace:
> > [  452.424516]  device_del+0x75/0x360
> > [  452.424518]  ? class_find_device+0x96/0xf0
> > [  452.424520]  device_unregister+0x16/0x60
> > [  452.424521]  device_destroy+0x3a/0x40
> > [  452.424525]  drm_dp_aux_unregister_devnode+0xea/0x180 [drm_kms_helper]
> > [  452.424534]  ? drm_dbg+0x87/0x90 [drm]
> > [  452.424538]  drm_dp_mst_topology_put_port+0x5b/0x110 [drm_kms_helper]
> > [  452.424543]  drm_dp_mst_topology_put_mstb+0xb6/0x180 [drm_kms_helper]
> > [  452.424547]  drm_dp_mst_topology_mgr_set_mst+0x233/0x2b0
> > [drm_kms_helper]
> > [  452.424551]  drm_dp_mst_topology_mgr_destroy+0x18/0xa0 [drm_kms_helper]
> > [  452.424571]  intel_dp_encoder_flush_work+0x32/0xb0 [i915]
> > [  452.424592]  intel_ddi_encoder_destroy+0x32/0x70 [i915]
> > [  452.424600]  drm_mode_config_cleanup+0x51/0x2e0 [drm]
> > [  452.424621]  intel_modeset_cleanup+0xc8/0x140 [i915]
> > [  452.424633]  i915_driver_unload+0xa8/0x130 [i915]
> > [  452.424645]  i915_pci_remove+0x1e/0x40 [i915]
> > [  452.424647]  pci_device_remove+0x3b/0xc0
> > [  452.424649]  device_release_driver_internal+0xe4/0x1d0
> > [  452.424651]  pci_stop_bus_device+0x69/0x90
> > [  452.424653]  pci_stop_and_remove_bus_device_locked+0x16/0x30
> > [  452.424655]  remove_store+0x75/0x90
> > [  452.424656]  kernfs_fop_write+0x116/0x190
> > [  452.424658]  vfs_write+0xa5/0x1a0
> > [  452.424660]  ksys_write+0x57/0xd0
> > [  452.424663]  do_syscall_64+0x55/0x150
> > [  452.424665]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [  452.424667] RIP: 0033:0x7f8cc1e7d038
> > [  452.424668] Code: 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00
> > f3 0f 1e fa 48 8d 05 e5 76 0d 00 8b 00 85 c0 75 17 b8 01 00 00 00 0f 05
> > <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 49 89 d4 55
> > [  452.424670] RSP: 002b:00007ffce4321218 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000001
> > [  452.424672] RAX: ffffffffffffffda RBX: 0000000000000002 RCX:
> > 00007f8cc1e7d038
> > [  452.424673] RDX: 0000000000000002 RSI: 000056515aefbf00 RDI:
> > 0000000000000001
> > [  452.424674] RBP: 000056515aefbf00 R08: 000000000000000a R09:
> > 00007f8cc1f0ee80
> > [  452.424675] R10: 000000000000000a R11: 0000000000000246 R12:
> > 00007f8cc1f50780
> > [  452.424676] R13: 0000000000000002 R14: 00007f8cc1f4b740 R15:
> > 0000000000000002
> > [  452.424678] WARNING: CPU: 3 PID: 1887 at fs/sysfs/group.c:256
> > sysfs_remove_group+0x76/0x80
> > [  452.424680] ---[ end trace a1c11eaf054910a3 ]---
> 
> **snip**
> 
> > So, we need to move the drm_dp_aux_register_devnode() call above the
> > connector
> > registration callback. Same goes for the port->aux.dev = port->connector-
> > > kdev; assignment that you do in patch 3/7 (and of course, you can remove
> > > the
> > connector registration status check there now).
> 
> Hmm, I don't think that will quite work for the purpose of the series.
> 
> If I register the aux device before the connector's, I wouldn't be able
> to set the connector's kdev as parent. The udev rules depend on this
> hierarchy to generate the symlinks we want - it reads the parent
> connector's attrs.

eesh, you're right-somehow I didn't notice that. Guess we'll need some sort of
other fix then

> 
> How are you reproducing this? I can try debugging this on an intel
> system. It looks like there's an expected 'power' attribute group that's
> missing when unregistering the aux device - I wonder where that gets
> attached.

I'm reproducing this just by reloading i915 on a machine with some MST
displays connected. I uploaded a copy of the script that I use to do this
here:

https://people.freedesktop.org/~lyudess/archive/06-03-2019/unloadgpumod.sh

Given a module (in this case drm.ko), it will go through and unload all of the
modules depending on it, then drm.ko, then reload.
> 
> Thanks,
> Leo
> 
> > > +
> > > +             drm_dp_aux_register_devnode(&port->aux);
> > >        }
-- 
Cheers,
	Lyude Paul

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