Re: [PATCH v2] PCI: qcom: Block accesses to downstream devices on link down

[Xilin Wu]

On 9/1/2026 8:39 PM, Konrad Dybcio wrote:
> On 9/1/26 2:35 PM, Manivannan Sadhasivam wrote:
> > On Wed, 19 Aug 2026 23:36:54 -0700, Qiang Yu wrote:
> > > After a PCIe link goes down, software may still access the BAR (MMIO)
> > > space or configuration space of devices behind that link before recovery
> > > has run. As the link is down, these accesses never complete, resulting in
> > > a storm of Completion Timeout AERs.
> > >
> > > Use the controller's ECAM blocker to drop these accesses to the PCIe
> > > address space as soon as the link-down interrupt fires, so that Completion
> > > Timeout AERs are reduced. The blocked range covers the entire address
> > > space (base 0x0, all-ones limit), since the Root Port's own DBI/iATU
> > > register space remains accessible regardless.
> > >
> > > [...]
> >
> > Applied, thanks!
> >
> > [1/1] PCI: qcom: Block accesses to downstream devices on link down
> >        commit: 86624b718f94517b26f96c1d7beb7632e5562afd
>
> Could this be a fix for
>
> https://lore.kernel.org/linux-arm-msm/b461c125-947b-4e06-b502-abb354e0cba6@xxxxxxxxxxxxxxxx/
>
> ?
>
> (+Xilin)

I'm not sure. Actually, we still have PCIe-related issues during reboot 
after reverting the flattened USB patch, though at a much lower 
occurrence rate.

I hope this series fixes it, but I haven't tested it yet.

https://patchwork.kernel.org/project/linux-arm-msm/list/?series=1151871&state=%2A&archive=both

Case 1 log:

Reboot count: 97
Reboot in 10 seconds, press any key to abort... [   12.260389] qcom-apm 
gprsvc:service:2:1: CMD timeout for [1001021] opcode
[   12.615536] qcom-soundwire 3210000.soundwire: din-ports (0) mismatch 
with controller (1)
[   12.626249] qcom-soundwire 3210000.soundwire: dout-ports (5) mismatch 
with controller (6)
[   39.120833] systemd-shutdown[1]: Failed to set watchdog hardware 
timeout to 10min: Invalid argument
[   40.341886] ------------[ cut here ]------------
[   40.346737] phy_check_link_status+0x0/0x118: returned: -16
[   40.352528] WARNING: drivers/net/phy/phy.c:1352 at 
_phy_state_machine+0x190/0x330, CPU#1: kworker/u32:2/72
[   40.362549] Modules linked in: q6prm_clocks q6apm_lpass_dais 
snd_q6dsp_common q6apm_dai q6prm joydev mousedev algif_hash 
algif_skcipher af_alg bnep rtw89_8852be rtw89_8852b rtw89_8852b_common 
rtw89_pci rtw89_core mac80211 qcom_iris cfg80211 videobuf2_dma_contig 
btusb v4l2_mem2mem btmtk videobuf2_memops btrtl btbcm videobuf2_v4l2 
libarc4 btintel videodev snd_soc_wcd938x bluetooth snd_soc_wcd938x_sdw 
snd_soc_wcd_classh videobuf2_common snd_soc_wcd_common snd_soc_sc8280xp 
rfkill mc snd_soc_qcom_common snd_soc_wcd_mbhc qcom_spmi_adc_tm5 
qcom_spmi_adc5 snd_soc_qcom_sdw soundwire_qcom qcom_vadc_common 
regmap_sdw snd_soc_lpass_tx_macro soundwire_bus snd_soc_lpass_rx_macro 
qcom_spmi_temp_alarm snd_q6apm snd_soc_lpass_va_macro radxa_svc_glink 
qcomtee snd_soc_lpass_macro_common slimbus sg fastrpc qcom_scm_storage 
platform_profile qcom_rng libcomposite uinput pmic_pdcharger_ulog 
nfnetlink dwmac_tc956x stmmac gpio_tc956x pcs_xpcs phylink rtc_ds1307 
at24 rpmsg_ctrl tc956x_pci qrtr_smd rpmsg_char qcom_pd_mapper uas qcom_pon
[   40.362750]  i2c_qcom_geni videocc_sm8350 camcc_sc8280xp 
qcom_q6v5_pas qcom_pil_info qcom_common qcom_refgen_regulator 
pinctrl_sc8280xp_lpass_lpi ucsi_glink qcom_glink_smem pinctrl_lpass_lpi 
qcom_q6v5 lpasscc_sc8280xp typec_ucsi qcom_sysmon qcom_wdt [last 
unloaded: 842_decompress]
[   40.480794] CPU: 1 UID: 0 PID: 72 Comm: kworker/u32:2 Not tainted 
7.0.11+ #38 PREEMPT(lazy)  a69a8d0b840e8538e5b93598a4d4312fb8da4861
[   40.493213] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   40.506435] Workqueue: events_power_efficient phy_state_machine
[   40.512577] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS 
BTYPE=--)
[   40.519788] pc : _phy_state_machine+0x190/0x330
[   40.524500] lr : _phy_state_machine+0x190/0x330
[   40.529209] sp : ffff800080a6bd20
[   40.532663] x29: ffff800080a6bd40 x28: 0000000000000000 x27: 
0000000000000000
[   40.540058] x26: ffff000080041028 x25: 0000000000000000 x24: 
ffff0000800c1605
[   40.547453] x23: ffff0000855b9cf8 x22: ffff000080041000 x21: 
0000000000000000
[   40.554845] x20: 0000000000000006 x19: ffff0000855b9800 x18: 
ffff3b3b60d68000
[   40.562236] x17: 000000040044ffff x16: ffffc4cc93b2a028 x15: 
ffffc4cc950c3c70
[   40.569632] x14: ffffc4cc94f8b480 x13: 0000000000000180 x12: 
ffff0007f5cf3480
[   40.577025] x11: 00000000000000c0 x10: 7ca63edf1413fc9b x9 : 
ffffc4cc92dc2df4
[   40.584427] x8 : ffff000080c9eba8 x7 : 0000000000000004 x6 : 
0000000000000000
[   40.591829] x5 : ffff3b3b60d68000 x4 : ffff000080c9da00 x3 : 
ffff00008e41da00
[   40.599223] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 
ffff000080c9da00
[   40.606625] Call trace:
[   40.609174]  _phy_state_machine+0x190/0x330 (P)
[   40.613878]  phy_state_machine+0x34/0xc0
[   40.617953]  process_one_work+0x194/0x570
[   40.622129]  worker_thread+0x18c/0x320
[   40.626033]  kthread+0x134/0x148
[   40.629399]  ret_from_fork+0x10/0x20
[   40.633127] ---[ end trace 0000000000000000 ]---
[   40.946101] SError Interrupt on CPU5, code 0x00000000be000011 -- SError
[   40.946109] CPU: 5 UID: 0 PID: 335 Comm: irq/277-aerdrv Tainted: G 
M    W           7.0.11+ #38 PREEMPT(lazy) 
a69a8d0b840e8538e5b93598a4d4312fb8da4861
[   40.946115] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   40.946116] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   40.946119] pstate: 204000c5 (nzCv daIF +PAN -UAO -TCO -DIT -SSBS 
BTYPE=--)
[   40.946121] pc : pci_generic_config_read+0x48/0xd0
[   40.946128] lr : pci_generic_config_read+0x2c/0xd0
[   40.946130] sp : ffff80008002bbb0
[   40.946132] x29: ffff80008002bbb0 x28: ffff000088fd9200 x27: 
ffffc4cc9599029f
[   40.946136] x26: ffffc4cc959902a0 x25: ffff000085a6b000 x24: 
ffffc4cc950bfd68
[   40.946138] x23: 0000000000000115 x22: 0000000000000100 x21: 
0000000000000000
[   40.946140] x20: 0000000000000004 x19: ffff80008002bbf4 x18: 
ffff3b3b60df4000
[   40.946142] x17: ffff3b3b60df4000 x16: ffff800080028000 x15: 
0000000000001900
[   40.946143] x14: 00000f423fffe700 x13: 0000000000000000 x12: 
000000000000af3b
[   40.946145] x11: 000000000000b67e x10: 00000000010b218c x9 : 
ffffc4cc937b28c4
[   40.946147] x8 : ffffc4cc937b2898 x7 : ffff00008b4a8800 x6 : 
ffffc4cc95ed5000
[   40.946148] x5 : ffff80008002bc30 x4 : ffff80008002bbf4 x3 : 
0000000000000000
[   40.946150] x2 : 0000000000000130 x1 : 0000000000000000 x0 : 
0000000000000000
[   40.946153] Kernel panic - not syncing: Asynchronous SError Interrupt
[   40.946156] CPU: 5 UID: 0 PID: 335 Comm: irq/277-aerdrv Tainted: G 
M    W           7.0.11+ #38 PREEMPT(lazy) 
a69a8d0b840e8538e5b93598a4d4312fb8da4861
[   40.946158] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   40.946159] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   40.946161] Call trace:
[   40.946162]  show_stack+0x20/0x38 (C)
[   40.946171]  dump_stack_lvl+0x7c/0xa0
[   40.946176]  dump_stack+0x18/0x2c
[   40.946178]  vpanic+0x2a8/0x4b8
[   40.946181]  panic+0x68/0x70
[   40.946182]  nmi_panic+0x74/0x80
[   40.946185]  arm64_serror_panic+0x78/0x90
[   40.946187]  arm64_is_fatal_ras_serror+0x90/0x98
[   40.946189]  do_serror+0x38/0x60
[   40.946191]  el1h_64_error_handler+0x40/0x70
[   40.946196]  el1h_64_error+0x84/0x88
[   40.946197]  pci_generic_config_read+0x48/0xd0 (P)
[   40.946198]  pci_bus_read_config_dword+0x80/0xf0
[   40.946199]  pci_read_config_dword+0x34/0x60
[   40.946201]  aer_irq+0x50/0xf8
[   40.946204]  __handle_irq_event_percpu+0x74/0x3d0
[   40.946208]  handle_irq_event+0x4c/0x120
[   40.946210]  handle_fasteoi_irq+0xfc/0x1b0
[   40.946213]  handle_irq_desc+0x3c/0x68
[   40.946215]  generic_handle_domain_irq+0x20/0x40
[   40.946217]  gic_handle_irq+0x168/0x300
[   40.946218]  do_interrupt_handler+0x58/0xa0
[   40.946219]  el1_interrupt+0x48/0xb0
[   40.946222]  el1h_64_irq_handler+0x18/0x28
[   40.946223]  el1h_64_irq+0x84/0x88
[   40.946225]  handle_softirqs+0xb0/0x4b0 (P)
[   40.946228]  __do_softirq+0x1c/0x28
[   40.946229]  ____do_softirq+0x18/0x30
[   40.946231]  call_on_irq_stack+0x30/0x48
[   40.946234]  do_softirq_own_stack+0x24/0x50
[   40.946236]  __irq_exit_rcu+0x13c/0x168
[   40.946238]  irq_exit_rcu+0x18/0x30
[   40.946240]  el1_interrupt+0x4c/0xb0
[   40.946242]  el1h_64_irq_handler+0x18/0x28
[   40.946244]  el1h_64_irq+0x84/0x88
[   40.946245]  _raw_spin_unlock_irqrestore+0x14/0x70 (P)
[   40.946248]  pci_read_config_dword+0x34/0x60
[   40.946249]  find_device_iter+0xbc/0x1e8
[   40.946251]  __pci_walk_bus+0x68/0xa0
[   40.946253]  __pci_walk_bus+0x4c/0xa0
[   40.946254]  __pci_walk_bus+0x4c/0xa0
[   40.946255]  pci_walk_bus+0x38/0x60
[   40.946257]  aer_isr_one_error_type+0x54/0x338
[   40.946259]  aer_isr_one_error+0x104/0x180
[   40.946261]  aer_isr+0x78/0x120
[   40.946263]  irq_thread_fn+0x30/0xb8
[   40.946264]  irq_thread+0x1a8/0x400
[   40.946265]  kthread+0x134/0x148
[   40.946268]  ret_from_fork+0x10/0x20
[   41.146728] Kernel Offset: 0x44cc12c80000 from 0xffff800080000000
[   41.146730] PHYS_OFFSET: 0xfff1000080000000
[   41.146731] CPU features: 0x2000000,002e0005,00230501,540172ab
[   41.146732] Memory Limit: none
[   41.565732] ---[ end Kernel panic - not syncing: Asynchronous SError 
Interrupt ]---

Case 2 log:

Reboot count: 65
Reboot in 10 seconds, press any key to abort... [   13.281893] qcom-apm 
gprsvc:service:2:1: CMD timeout for [1001021] opcode
[   13.340861] qcom-soundwire 3210000.soundwire: din-ports (0) mismatch 
with controller (1)
[   13.351390] qcom-soundwire 3210000.soundwire: dout-ports (5) mismatch 
with controller (6)
[   41.120391] systemd-shutdown[1]: Failed to set watchdog hardware 
timeout to 10min: Invalid argument
[   42.128807] pcieport 0004:00:00.0: PCIe Bus Error: 
severity=Uncorrectable (Non-Fatal), type=Transaction Layer, (Requester ID)
[   42.140459] pcieport 0004:00:00.0:   device [17cb:010e] error 
status/mask=00004000/00400000
[   42.149053] pcieport 0004:00:00.0:    [14] CmpltTO                (First)
[   42.302328] ------------[ cut here ]------------
[   42.307148] phy_check_link_status+0x0/0x118: returned: -16
[   42.312945] WARNING: drivers/net/phy/phy.c:1352 at 
_phy_state_machine+0x190/0x330, CPU#3: kworker/u32:0/12
[   42.322951] Modules linked in: q6prm_clocks q6apm_lpass_dais 
snd_q6dsp_common q6prm q6apm_dai joydev mousedev algif_hash 
algif_skcipher af_alg bnep zram 842_decompress 842_compress 
lz4hc_compress lz4_compress rtw89_8852be rtw89_8852b rtw89_8852b_common 
rtw89_pci rtw89_core btusb mac80211 btmtk qcom_iris btrtl btbcm cfg80211 
videobuf2_dma_contig btintel v4l2_mem2mem videobuf2_memops libarc4 
videobuf2_v4l2 snd_soc_wcd938x bluetooth snd_soc_wcd938x_sdw videodev 
snd_soc_wcd_classh rfkill snd_soc_wcd_common snd_soc_wcd_mbhc regmap_sdw 
snd_soc_sc8280xp videobuf2_common qcom_spmi_adc_tm5 snd_soc_qcom_common 
qcom_spmi_adc5 snd_soc_lpass_tx_macro snd_soc_qcom_sdw 
snd_soc_lpass_va_macro snd_soc_lpass_rx_macro mc qcom_vadc_common 
snd_q6apm soundwire_qcom snd_soc_lpass_macro_common soundwire_bus 
qcom_spmi_temp_alarm radxa_svc_glink fastrpc qcom_scm_storage slimbus sg 
platform_profile qcomtee qcom_rng libcomposite uinput 
pmic_pdcharger_ulog nfnetlink rpmsg_ctrl rpmsg_char qrtr_smd 
dwmac_tc956x stmmac qcom_pd_mapper pcs_xpcs
[   42.323138]  phylink
[   42.415567]  gpio_tc956x qcom_q6v5_pas qcom_pil_info rtc_ds1307 at24 
qcom_common qcom_glink_smem tc956x_pci uas qcom_pon camcc_sc8280xp 
pinctrl_sc8280xp_lpass_lpi videocc_sm8350 i2c_qcom_geni 
qcom_refgen_regulator pinctrl_lpass_lpi ucsi_glink lpasscc_sc8280xp 
qcom_q6v5 qcom_wdt qcom_sysmon typec_ucsi
[   42.445394] CPU: 3 UID: 0 PID: 12 Comm: kworker/u32:0 Not tainted 
7.0.11+ #37 PREEMPT(lazy)  452f60429f6b383145c5e2c98b90ac68d2bd4e3a
[   42.457814] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   42.471031] Workqueue: events_power_efficient phy_state_machine
[   42.477171] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS 
BTYPE=--)
[   42.484381] pc : _phy_state_machine+0x190/0x330
[   42.489080] lr : _phy_state_machine+0x190/0x330
[   42.493790] sp : ffff8000800e3d20
[   42.497233] x29: ffff8000800e3d40 x28: 0000000000000000 x27: 
0000000000000000
[   42.504629] x26: ffff000080041028 x25: 0000000000000000 x24: 
ffff0000800c2a05
[   42.512024] x23: ffff000085e524f8 x22: ffff000080041000 x21: 
0000000000000000
[   42.519419] x20: 0000000000000006 x19: ffff000085e52000 x18: 
ffff59480c02f000
[   42.526813] x17: ffff59480c02f000 x16: ffffa6bfe88a8cc8 x15: 
ffffa6bfe9e43c70
[   42.534206] x14: ffffa6bfe9d0b480 x13: 0000000000000180 x12: 
ffff0007f5d3a480
[   42.541598] x11: 00000000000000c0 x10: 71e4c81c85622a03 x9 : 
ffffa6bfe7b42df4
[   42.548992] x8 : ffff0000808d47a8 x7 : 0000000000000004 x6 : 
0000000000000000
[   42.556387] x5 : ffff59480c02f000 x4 : ffff0000808d3600 x3 : 
ffff000081c9b600
[   42.563777] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 
ffff0000808d3600
[   42.571174] Call trace:
[   42.573724]  _phy_state_machine+0x190/0x330 (P)
[   42.578438]  phy_state_machine+0x34/0xc0
[   42.582513]  process_one_work+0x194/0x570
[   42.586688]  worker_thread+0x18c/0x320
[   42.590592]  kthread+0x134/0x148
[   42.593953]  ret_from_fork+0x10/0x20
[   42.597680] ---[ end trace 0000000000000000 ]---
[   43.035576] SError Interrupt on CPU5, code 0x00000000be000011 -- SError
[   43.035582] CPU: 5 UID: 0 PID: 0 Comm: swapper/5 Tainted: G   M    W 
         7.0.11+ #37 PREEMPT(lazy) 
452f60429f6b383145c5e2c98b90ac68d2bd4e3a
[   43.035586] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   43.035587] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   43.035588] pstate: 204000c5 (nzCv daIF +PAN -UAO -TCO -DIT -SSBS 
BTYPE=--)
[   43.035590] pc : pci_generic_config_read+0x48/0xd0
[   43.035595] lr : pci_generic_config_read+0x2c/0xd0
[   43.035596] sp : ffff80008002be00
[   43.035597] x29: ffff80008002be00 x28: ffff0000808f4800 x27: 
ffffa6bfea71029f
[   43.035600] x26: ffffa6bfea7102a0 x25: ffff000085926e00 x24: 
ffffa6bfe9e3fd68
[   43.035601] x23: 0000000000000105 x22: 0000000000000020 x21: 
0000000000000000
[   43.035603] x20: 0000000000000004 x19: ffff80008002be44 x18: 
ffff59480c075000
[   43.035604] x17: ffff59480c075000 x16: ffff800080028000 x15: 
0000000000000000
[   43.035606] x14: ffff0000808f4800 x13: ffff59480c075000 x12: 
00000000b474d91d
[   43.035607] x11: 0000000000000000 x10: 0000000000001000 x9 : 
ffffa6bfe85328c4
[   43.035609] x8 : ffffa6bfe8532898 x7 : ffff0007f7eb4800 x6 : 
ffffa6bfeac55000
[   43.035610] x5 : ffff80008002bea4 x4 : ffff80008002be44 x3 : 
0000000000000000
[   43.035612] x2 : 0000000000000090 x1 : 0000000000000000 x0 : 
0000000000000000
[   43.035614] Kernel panic - not syncing: Asynchronous SError Interrupt
[   43.035615] CPU: 5 UID: 0 PID: 0 Comm: swapper/5 Tainted: G   M    W 
         7.0.11+ #37 PREEMPT(lazy) 
452f60429f6b383145c5e2c98b90ac68d2bd4e3a
[   43.035617] Tainted: [M]=MACHINE_CHECK, [W]=WARN
[   43.035618] Hardware name: Radxa Computer Co., Ltd. Radxa Dragon 
Q8B/RS782-D16S32W0, BIOS 6.0.260812.BOOT.MXF.1.1.c1-00167-MAKENA-1 
08/12/2026
[   43.035619] Call trace:
[   43.035621]  show_stack+0x20/0x38 (C)
[   43.035629]  dump_stack_lvl+0x7c/0xa0
[   43.035633]  dump_stack+0x18/0x2c
[   43.035635]  vpanic+0x2a8/0x4b8
[   43.035637]  panic+0x68/0x70
[   43.035639]  nmi_panic+0x74/0x80
[   43.035641]  arm64_serror_panic+0x78/0x90
[   43.035644]  arm64_is_fatal_ras_serror+0x90/0x98
[   43.035646]  do_serror+0x38/0x60
[   43.035648]  el1h_64_error_handler+0x40/0x70
[   43.035651]  el1h_64_error+0x84/0x88
[   43.035652]  pci_generic_config_read+0x48/0xd0 (P)
[   43.035653]  pci_bus_read_config_dword+0x80/0xf0
[   43.035656]  pcie_capability_read_dword+0x90/0xc0
[   43.035657]  pcie_pme_irq+0x58/0xf0
[   43.035660]  __handle_irq_event_percpu+0x74/0x3d0
[   43.035664]  handle_irq_event+0x4c/0x120
[   43.035666]  handle_fasteoi_irq+0xfc/0x1b0
[   43.035668]  handle_irq_desc+0x3c/0x68
[   43.035670]  generic_handle_domain_irq+0x20/0x40
[   43.035672]  gic_handle_irq+0x168/0x300
[   43.035673]  call_on_irq_stack+0x30/0x48
[   43.035675]  do_interrupt_handler+0x88/0xa0
[   43.035676]  el1_interrupt+0x48/0xb0
[   43.035679]  el1h_64_irq_handler+0x18/0x28
[   43.035680]  el1h_64_irq+0x84/0x88
[   43.035681]  cpuidle_enter_state+0xc4/0x7c0 (P)
[   43.035682]  cpuidle_enter+0x3c/0x60
[   43.035686]  do_idle+0x168/0x320
[   43.035688]  cpu_startup_entry+0x3c/0x50
[   43.035689]  secondary_start_kernel+0x13c/0x180
[   43.035691]  __secondary_switched+0xc0/0xc8
[   43.036060] SError Interrupt on CPU4, code 0x00000000be000411 -- SError
[   43.237107] Kernel Offset: 0x26bf67a00000 from 0xffff800080000000
[   43.237109] PHYS_OFFSET: 0xfff1000080000000
[   43.237109] CPU features: 0x2000000,002e0005,00230501,540172ab
[   43.237111] Memory Limit: none
[   43.595524] ---[ end Kernel panic - not syncing: Asynchronous SError 
Interrupt ]---

> Konrad


--
Best regards,
Xilin Wu <sophon@xxxxxxxxx>