On most systems with ACPI hotplugging support, it seems that we always receive a hotplug event once we re-enable EC interrupts even if the GPU hasn't even been resumed yet.
This can cause problems since even though we schedule hpd_work to handle connector reprobing for us, hpd_work synchronizes on pm_runtime_get_sync() to wait until the device is ready to perform reprobing. Since runtime suspend/resume callbacks are disabled before the PM core calls ->suspend(), any calls to pm_runtime_get_sync() during this period will grab a runtime PM ref and return immediately with -EACCES. Because we schedule hpd_work from our ACPI HPD handler, and hpd_work synchronizes on pm_runtime_get_sync(), this causes us to launch a connector reprobe immediately even if the GPU isn't actually resumed just yet. This causes various warnings in dmesg and occasionally, also prevents some displays connected to the dedicated GPU from coming back up after suspend. Example:
usb 1-4: USB disconnect, device number 14 usb 1-4.1: USB disconnect, device number 15 WARNING: CPU: 0 PID: 838 at drivers/gpu/drm/nouveau/include/nvkm/subdev/i2c.h:170 nouveau_dp_detect+0x17e/0x370 [nouveau] CPU: 0 PID: 838 Comm: kworker/0:6 Not tainted 4.17.14-201.Lyude.bz1477182.V3.fc28.x86_64 #1 Hardware name: LENOVO 20EQS64N00/20EQS64N00, BIOS N1EET77W (1.50 ) 03/28/2018 Workqueue: events nouveau_display_hpd_work [nouveau] RIP: 0010:nouveau_dp_detect+0x17e/0x370 [nouveau] RSP: 0018:ffffa15143933cf0 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff8cb4f656c400 RCX: 0000000000000000 RDX: ffffa1514500e4e4 RSI: ffffa1514500e4e4 RDI: 0000000001009002 RBP: ffff8cb4f4a8a800 R08: ffffa15143933cfd R09: ffffa15143933cfc R10: 0000000000000000 R11: 0000000000000000 R12: ffff8cb4fb57a000 R13: ffff8cb4fb57a000 R14: ffff8cb4f4a8f800 R15: ffff8cb4f656c418 FS: 0000000000000000(0000) GS:ffff8cb51f400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f78ec938000 CR3: 000000073720a003 CR4: 00000000003606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? _cond_resched+0x15/0x30 nouveau_connector_detect+0x2ce/0x520 [nouveau] ? _cond_resched+0x15/0x30 ? ww_mutex_lock+0x12/0x40 drm_helper_probe_detect_ctx+0x8b/0xe0 [drm_kms_helper] drm_helper_hpd_irq_event+0xa8/0x120 [drm_kms_helper] nouveau_display_hpd_work+0x2a/0x60 [nouveau] process_one_work+0x187/0x340 worker_thread+0x2e/0x380 ? pwq_unbound_release_workfn+0xd0/0xd0 kthread+0x112/0x130 ? kthread_create_worker_on_cpu+0x70/0x70 ret_from_fork+0x35/0x40 Code: 4c 8d 44 24 0d b9 00 05 00 00 48 89 ef ba 09 00 00 00 be 01 00 00 00 e8 e1 09 f8 ff 85 c0 0f 85 b2 01 00 00 80 7c 24 0c 03 74 02 <0f> 0b 48 89 ef e8 b8 07 f8 ff f6 05 51 1b c8 ff 02 0f 84 72 ff ---[ end trace 55d811b38fc8e71a ]---
So, to fix this we attempt to grab a runtime PM reference in the ACPI handler itself asynchronously. If the GPU is already awake (it will have normal hotplugging at this point) or runtime PM callbacks are currently disabled on the device, we drop our reference without updating the autosuspend delay. We only schedule connector reprobes when we successfully managed to queue up a resume request with our asynchronous PM ref.
This also has the added benefit of preventing redundant connector reprobes from ACPI while the GPU is runtime resumed!
Signed-off-by: Lyude Paul lyude@redhat.com Cc: stable@vger.kernel.org Cc: Karol Herbst kherbst@redhat.com Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1477182#c41
Signed-off-by: Lyude Paul lyude@redhat.com --- drivers/gpu/drm/nouveau/nouveau_display.c | 26 +++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c index 4b873e668b26..2e3226ff9f95 100644 --- a/drivers/gpu/drm/nouveau/nouveau_display.c +++ b/drivers/gpu/drm/nouveau/nouveau_display.c @@ -377,15 +377,29 @@ nouveau_display_acpi_ntfy(struct notifier_block *nb, unsigned long val, { struct nouveau_drm *drm = container_of(nb, typeof(*drm), acpi_nb); struct acpi_bus_event *info = data; + int ret;
if (!strcmp(info->device_class, ACPI_VIDEO_CLASS)) { if (info->type == ACPI_VIDEO_NOTIFY_PROBE) { - /* - * This may be the only indication we receive of a - * connector hotplug on a runtime suspended GPU, - * schedule hpd_work to check. - */ - schedule_work(&drm->hpd_work); + ret = pm_runtime_get(drm->dev->dev); + if (ret == 1 || ret == -EACCES) { + /* If the GPU is already awake, or in a state + * where we can't wake it up, it can handle + * it's own hotplug events. + */ + pm_runtime_put_autosuspend(drm->dev->dev); + } else if (ret == 0) { + /* This may be the only indication we receive + * of a connector hotplug on a runtime + * suspended GPU, schedule hpd_work to check. + */ + NV_DEBUG(drm, "ACPI requested connector reprobe\n"); + schedule_work(&drm->hpd_work); + pm_runtime_put_noidle(drm->dev->dev); + } else { + NV_WARN(drm, "Dropped ACPI reprobe event due to RPM error: %d\n", + ret); + }
/* acpi-video should not generate keypresses for this */ return NOTIFY_BAD;