Hi, i'm currently experiment with suspend to idle on the Raspberry Pi [1]. During my tests, i noticed a WARNING of the vc4 during suspend incl. Runtime PM usage count underflow. It would be nice if someone can look at it. In case you want to reproduce it, i can prepare a branch with some improvements/hacks. For example i disabled dwc2/USB because it cause a lot of trouble during resume. Here are the steps to trigger this issue: - make sure necessary kernel options are enabled ( CONFIG_SUSPEND, CONFIG_PM_DEBUG, CONFIG_PM_ADVANCED_DEBUG ) - make sure no HDMI cable is connected to Raspberry Pi 3 Plus - Add "no_console_suspend" to cmdline.txt and reboot - Connect via Debug UART: echo 1 > /sys/power/pm_debug_messages echo platform > /sys/power/pm_test echo freeze > /sys/power/state Here is the output: [ 75.538497] PM: suspend entry (s2idle) [ 76.915786] Filesystems sync: 1.377 seconds [ 79.678262] rpi_firmware_set_power: Set HDMI to 1 [ 79.678634] rpi_firmware_set_power: Set HDMI to 0 [ 79.850949] Freezing user space processes [ 79.852460] Freezing user space processes completed (elapsed 0.001 seconds) [ 79.852484] OOM killer disabled. [ 79.852493] Freezing remaining freezable tasks [ 79.853684] Freezing remaining freezable tasks completed (elapsed 0.001 seconds) [ 80.892819] ieee80211 phy0: brcmf_fil_cmd_data: bus is down. we have nothing to do. [ 80.892843] ieee80211 phy0: brcmf_cfg80211_get_tx_power: error (-5) [ 81.514053] PM: suspend of devices complete after 1659.336 msecs [ 81.514089] PM: start suspend of devices complete after 1660.386 msecs [ 81.515616] PM: late suspend of devices complete after 1.509 msecs [ 81.515938] rpi_firmware_set_power: Set VEC to 0 [ 81.516010] rpi_firmware_set_power: Set V3D to 0 [ 81.516998] PM: noirq suspend of devices complete after 1.239 msecs [ 81.517016] PM: suspend debug: Waiting for 5 second(s). [ 89.598310] rpi_firmware_set_power: Set V3D to 1 [ 90.078228] ------------[ cut here ]------------ [ 90.078240] WARNING: CPU: 1 PID: 216 at drivers/gpu/drm/vc4/vc4_hdmi.c:477 vc4_hdmi_connector_detect_ctx+0x2e4/0x34c [vc4] [ 90.078344] Modules linked in: aes_arm aes_generic cbc crypto_simd cryptd algif_skcipher af_alg brcmfmac_wcc brcmfmac vc4 brcmutil snd_soc_hdmi_codec snd_soc_core ac97_bus sha256_generic snd_pcm_dmaengine libsha256 snd_pcm sha256_arm snd_timer hci_uart cfg80211 btbcm snd bluetooth soundcore drm_dma_helper crc32_arm_ce ecdh_generic ecc raspberrypi_hwmon libaes bcm2835_thermal [ 90.078551] CPU: 1 PID: 216 Comm: kworker/1:2 Not tainted 6.9.3-dirty #30 [ 90.078568] Hardware name: BCM2835 [ 90.078580] Workqueue: events output_poll_execute [ 90.078610] Call trace: [ 90.078624] unwind_backtrace from show_stack+0x10/0x14 [ 90.078660] show_stack from dump_stack_lvl+0x50/0x64 [ 90.078688] dump_stack_lvl from __warn+0x7c/0x124 [ 90.078723] __warn from warn_slowpath_fmt+0x170/0x178 [ 90.078760] warn_slowpath_fmt from vc4_hdmi_connector_detect_ctx+0x2e4/0x34c [vc4] [ 90.078862] vc4_hdmi_connector_detect_ctx [vc4] from drm_helper_probe_detect_ctx+0x40/0x120 [ 90.078951] drm_helper_probe_detect_ctx from output_poll_execute+0x160/0x24c [ 90.078982] output_poll_execute from process_one_work+0x16c/0x3b4 [ 90.079012] process_one_work from worker_thread+0x270/0x488 [ 90.079036] worker_thread from kthread+0xe0/0xfc [ 90.079060] kthread from ret_from_fork+0x14/0x28 [ 90.079080] Exception stack(0xf0af9fb0 to 0xf0af9ff8) [ 90.079096] 9fa0: 00000000 00000000 00000000 00000000 [ 90.079113] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 90.079129] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 [ 90.079141] ---[ end trace 0000000000000000 ]--- [ 90.079155] vc4_hdmi 3f902000.hdmi: vc4_hdmi_connector_detect_ctx: pm_runtime_resume_and_get failed: -13 [ 92.638262] rpi_firmware_set_power: Set HDMI to 1 [ 95.678251] rpi_firmware_set_power: Set VEC to 1 [ 95.678380] PM: noirq resume of devices complete after 9160.930 msecs [ 95.679604] PM: early resume of devices complete after 1.069 msecs [ 95.812230] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6 [ 95.812282] PM: resume of devices complete after 132.657 msecs [ 95.813246] vc4_hdmi 3f902000.hdmi: Runtime PM usage count underflow! [ 95.814456] OOM killer enabled. [ 95.814466] Restarting tasks ... done. [ 95.817193] random: crng reseeded on system resumption [ 95.819813] rpi_firmware_set_power: Set HDMI to 0 [ 95.827808] PM: suspend exit [1] - https://github.com/raspberrypi/firmware/issues/1894
