Re: [PATCH v2] PCI: imx6: Add suspend/resume support for i.MX6QDL

From: Stefan Eichenberger
Date: Mon Oct 14 2024 - 04:11:11 EST

Hi Richard and Frank,

On Sat, Oct 12, 2024 at 09:02:28AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Stefan Eichenberger <eichest@xxxxxxxxx>
> > Sent: 2024年10月11日 22:36
> > To: Frank Li <frank.li@xxxxxxx>
> > Cc: Francesco Dolcini <francesco@xxxxxxxxxx>; Hongxing Zhu
> > <hongxing.zhu@xxxxxxx>; l.stach@xxxxxxxxxxxxxx; lpieralisi@xxxxxxxxxx;
> > kw@xxxxxxxxx; manivannan.sadhasivam@xxxxxxxxxx; robh@xxxxxxxxxx;
> > bhelgaas@xxxxxxxxxx; shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> > kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; Francesco Dolcini
> > <francesco.dolcini@xxxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx;
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; Stefan Eichenberger
> > <stefan.eichenberger@xxxxxxxxxxx>
> > Subject: Re: [PATCH v2] PCI: imx6: Add suspend/resume support for i.MX6QDL
> >
> > Hi Frank,
> >
> > On Thu, Oct 10, 2024 at 06:45:17PM -0400, Frank Li wrote:
> > > On Thu, Oct 10, 2024 at 10:11:21PM +0200, Francesco Dolcini wrote:
> > > > Hello Frank,
> > > >
> > > > On Thu, Oct 10, 2024 at 04:01:21PM -0400, Frank Li wrote:
> > > > > On Wed, Oct 09, 2024 at 03:14:05PM +0200, Stefan Eichenberger wrote:
> > > > > > From: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
> > > > > >
> > > > > > The suspend/resume support is broken on the i.MX6QDL platform.
> > > > > > This patch resets the link upon resuming to recover
> > > > > > functionality. It shares most of the sequences with other i.MX
> > > > > > devices but does not touch the critical registers, which might
> > > > > > break PCIe. This patch addresses the same issue as the following
> > downstream commit:
> > > > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%
> > > > > >
> > 2Fgithub.com%2Fnxp-imx%2Flinux-imx%2Fcommit%2F4e92355e1f79d225ea
> > > > > >
> > 842511fcfd42b343b32995&data=05%7C02%7Chongxing.zhu%40nxp.com%7C4
> > > > > >
> > 9cdf8aaeee54cec71c508dcea0215b1%7C686ea1d3bc2b4c6fa92cd99c5c3016
> > > > > >
> > 35%7C0%7C0%7C638642541899874406%7CUnknown%7CTWFpbGZsb3d8eyJWI
> > joi
> > > > > >
> > MC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7
> > > > > >
> > C%7C%7C&sdata=DQGwcXYy0soCov1Uf4ycLQiisP8qlbBzOslyX3FY5Cs%3D&res
> > > > > > erved=0 In comparison this patch will also reset the device if
> > > > > > possible. Without this patch suspend/resume will not work if a
> > > > > > PCIe device is connected.
> > > > > > The kernel will hang on resume and print an error:
> > > > > > ath10k_pci 0000:01:00.0: Unable to change power state from D3hot
> > > > > > to D0, device inaccessible
> > > > > > 8<--- cut here ---
> > > > > > Unhandled fault: imprecise external abort (0x1406) at 0x0106f944
> > > > > >
> > > > > > Signed-off-by: Stefan Eichenberger
> > > > > > <stefan.eichenberger@xxxxxxxxxxx>
> > > > > > ---
> > > > >
> > > > > Thank you for your patch.
> > > > >
> > > > > But it may conflict with another suspend/resume patch
> > > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > > lore.kernel.org%2Fimx%2F1727245477-15961-8-git-send-email-hongxing
> > > > > .zhu%40nxp.com%2F&data=05%7C02%7Chongxing.zhu%40nxp.com%7C4
> > 9cdf8aa
> > > > >
> > eee54cec71c508dcea0215b1%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%
> > 7C
> > > > >
> > 0%7C638642541899892894%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjA
> > wMDA
> > > > >
> > iLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata
> > > > >
> > =xPBKoiWL8IceLlv%2F6lWoqkPWosh%2BRvG8jyA8NjKSsOI%3D&reserved=0
> > > >
> > > > Thanks for the head-up.
> > > >
> > > > Do you see any issue with this patch apart that? Because this patch
> > > > is fixing a crash, so I would expect this to be merged, once ready,
> > > > and such a series rebased afterward.
> > > >
> > > > I am writing this explicitly since you wrote a similar comment on
> > > > the
> > > > v1
> > > > (https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fl
> > > > ore.kernel.org%2Fall%2FZsNXDq%252FkidZdyhvD%40lizhi-Precision-Tower-
> > > >
> > 5810%2F&data=05%7C02%7Chongxing.zhu%40nxp.com%7C49cdf8aaeee54cec
> > 71c5
> > > >
> > 08dcea0215b1%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C63864
> > 25418
> > > >
> > 99904634%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2l
> > uMzI
> > > >
> > iLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=x2OVvZsi4YIxSg
> > KGD
> > > > 7ZzqbRQjiTFK4%2BzMdgDv2qSdig%3D&reserved=0)
> > > > and I would like to prevent to have this fix starving for long just
> > > > because multiple people is working on the same driver.
> > >
> > > My key comment for this patch is use flags IMX_PCIE_FLAG_SKIP_TURN_OFF
> > > in suspend()/resume(), it is up to kw to pick which one firstly.
> >
> > I will try to implement it as you proposed with the new flag.
> >
> > However, what I figured out with kernel v6.12-rc1 I get the following warning
> > when booting on an i.MX6QDL even without my patch applied:
> > [ 1.901199] PCI: bus0: Fast back to back transfers disabled
> > [ 1.904754] mmc1: SDHCI controller on 2190000.mmc [2190000.mmc]
> > using ADMA
> > [ 1.904914] mmc2: SDHCI controller on 2194000.mmc [2194000.mmc]
> > using ADMA
> > [ 1.910686] pci 0000:01:00.0: [168c:003c] type 00 class 0x028000 PCIe
> > Endpoint
> > [ 1.918390] NET: Registered PF_PACKET protocol family
> > [ 1.918573] mmc0: SDHCI controller on 2198000.mmc [2198000.mmc]
> > using ADMA
> > [ 1.924322] pci 0000:01:00.0: BAR 0 [mem 0x00000000-0x001fffff 64bit]
> > [ 1.931635] Key type dns_resolver registered
> > [ 1.936764] pci 0000:01:00.0: ROM [mem 0x00000000-0x0000ffff pref]
> > [ 1.961043] pci 0000:01:00.0: supports D1 D2
> > [ 1.961526] Registering SWP/SWPB emulation handler
> > [ 1.965601] mmc0: new DDR MMC card at address 0001
> > [ 1.976575] mmcblk0: mmc0:0001 Q2J54A 3.59 GiB
> > [ 1.979794] Loading compiled-in X.509 certificates
> > [ 1.985036] PCI: bus1: Fast back to back transfers disabled
> > [ 1.991531] pci 0000:00:00.0: bridge window [mem 0x01000000-0x011fffff]:
> > assigned
> > [ 1.998742] mmcblk0: p1 p2 p3
> > [ 1.999163] pci 0000:00:00.0: BAR 0 [mem 0x01200000-0x012fffff]:
> > assigned
> > [ 2.003947] mmcblk0boot0: mmc0:0001 Q2J54A 16.0 MiB
> > [ 2.008990] pci 0000:00:00.0: bridge window [mem 0x01300000-0x013fffff
> > pref]: assigned
> > [ 2.009023] pci 0000:00:00.0: ROM [mem 0x01400000-0x0140ffff pref]:
> > assigned
> > [ 2.009054] pci 0000:01:00.0: BAR 0 [mem 0x01000000-0x011fffff 64bit]:
> > assigned
> > [ 2.017526] mmcblk0boot1: mmc0:0001 Q2J54A 16.0 MiB
> > [ 2.022015] pci 0000:01:00.0: ROM [mem 0x01300000-0x0130ffff pref]:
> > assigned
> > [ 2.032133] mmcblk0rpmb: mmc0:0001 Q2J54A 512 KiB, chardev (242:0)
> > [ 2.036347] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
> > [ 2.036370] pci 0000:00:00.0: bridge window [mem
> > 0x01000000-0x011fffff]
> > [ 2.036384] pci 0000:00:00.0: bridge window [mem
> > 0x01300000-0x013fffff pref]
> > [ 2.042552] pps pps0: new PPS source ptp0
> > [ 2.048338] pci_bus 0000:00: resource 4 [io 0x0000-0xffff]
> > [ 2.083626] pci_bus 0000:00: resource 5 [mem 0x01000000-0x01efffff]
> > [ 2.089972] pci_bus 0000:01: resource 1 [mem 0x01000000-0x011fffff]
> > [ 2.093461] fec 2188000.ethernet eth0: registered PHC device 0
> > [ 2.096283] pci_bus 0000:01: resource 2 [mem 0x01300000-0x013fffff pref]
> > [ 2.096352] sysfs: cannot create duplicate filename
> > '/devices/platform/soc/1ffc000.pcie/pci0000:00/0000:00:00.0/resource0'
> > [ 2.096365] CPU: 3 UID: 0 PID: 52 Comm: kworker/u19:2 Not tainted
> > 6.12.0-rc1 #54
> > [ 2.096381] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> > [ 2.096391] Workqueue: async async_run_entry_fn
> > [ 2.103025] imx_thermal 20c8000.anatop:tempmon: Industrial CPU
> > temperature grade - max:105C critical:100C passive:95C
> > [ 2.108932]
> > [ 2.108940] Call trace:
> > [ 2.108950] unwind_backtrace from show_stack+0x10/0x14
> > [ 2.121391] clk: Disabling unused clocks
> > [ 2.127423] show_stack from dump_stack_lvl+0x54/0x68
> > [ 2.127451] dump_stack_lvl from sysfs_warn_dup+0x58/0x64
> > [ 2.134265] PM: genpd: Disabling unused power domains
> > [ 2.138525] sysfs_warn_dup from sysfs_add_bin_file_mode_ns+0xbc/0xcc
> > [ 2.138547] sysfs_add_bin_file_mode_ns from
> > sysfs_create_bin_file+0xac/0xb4
> > [ 2.149242] ALSA device list:
> > [ 2.150647] sysfs_create_bin_file from
> > pci_create_resource_files+0x84/0x148
> > [ 2.153183] No soundcards found.
> > [ 2.158407] pci_create_resource_files from
> > pci_bus_add_device+0x24/0xe4
> > [ 2.211699] pci_bus_add_device from pci_bus_add_devices+0x2c/0x70
> > [ 2.217930] pci_bus_add_devices from pci_host_probe+0x7c/0xa4
> > [ 2.223806] pci_host_probe from dw_pcie_host_init+0x4ec/0x71c
> > [ 2.229682] dw_pcie_host_init from imx_pcie_probe+0x3a8/0x75c
> > [ 2.235559] imx_pcie_probe from platform_probe+0x5c/0xb0
> > [ 2.241010] platform_probe from really_probe+0xd0/0x3a4
> > [ 2.246364] really_probe from __driver_probe_device+0x8c/0x1d4
> > [ 2.252321] __driver_probe_device from driver_probe_device+0x30/0xc0
> > [ 2.258803] driver_probe_device from
> > __driver_attach_async_helper+0x50/0xd8
> > [ 2.265892] __driver_attach_async_helper from
> > async_run_entry_fn+0x30/0x144
> > [ 2.272980] async_run_entry_fn from process_one_work+0x154/0x2dc
> > [ 2.279115] process_one_work from worker_thread+0x250/0x3f0
> > [ 2.284811] worker_thread from kthread+0x110/0x12c
> > [ 2.289726] kthread from ret_from_fork+0x14/0x28
> > [ 2.294461] Exception stack(0xe6a0dfb0 to 0xe6a0dff8)
> > [ 2.299535] dfa0: 00000000
> > 00000000 00000000 00000000
> > [ 2.307740] dfc0: 00000000 00000000 00000000 00000000 00000000
> > 00000000 00000000 00000000
> > [ 2.315942] dfe0: 00000000 00000000 00000000 00000000 00000013
> > 00000000
> > [ 2.323156] pcieport 0000:00:00.0: PME: Signaling with IRQ 293
> > [ 2.329645] pcieport 0000:00:00.0: AER: enabled with IRQ 293
> > [ 2.335553] sysfs: cannot create duplicate filename
> > '/devices/platform/soc/1ffc000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0/res
> > ource0'
> > [ 2.347794] CPU: 3 UID: 0 PID: 52 Comm: kworker/u19:2 Not tainted
> > 6.12.0-rc1 #54
> > [ 2.355229] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> > [ 2.361779] Workqueue: async async_run_entry_fn
> > [ 2.366349] Call trace:
> > [ 2.366362] unwind_backtrace from show_stack+0x10/0x14
> > [ 2.374183] show_stack from dump_stack_lvl+0x54/0x68
> > [ 2.379273] dump_stack_lvl from sysfs_warn_dup+0x58/0x64
> > [ 2.384706] sysfs_warn_dup from sysfs_add_bin_file_mode_ns+0xbc/0xcc
> > [ 2.391183] sysfs_add_bin_file_mode_ns from
> > sysfs_create_bin_file+0xac/0xb4
> > [ 2.398270] sysfs_create_bin_file from
> > pci_create_resource_files+0x84/0x148
> > [ 2.405360] pci_create_resource_files from
> > pci_bus_add_device+0x24/0xe4
> > [ 2.412113] pci_bus_add_device from pci_bus_add_devices+0x2c/0x70
> > [ 2.418334] pci_bus_add_devices from pci_bus_add_devices+0x60/0x70
> > [ 2.424642] pci_bus_add_devices from pci_host_probe+0x7c/0xa4
> > [ 2.430511] pci_host_probe from dw_pcie_host_init+0x4ec/0x71c
> > [ 2.436384] dw_pcie_host_init from imx_pcie_probe+0x3a8/0x75c
> > [ 2.442258] imx_pcie_probe from platform_probe+0x5c/0xb0
> > [ 2.447704] platform_probe from really_probe+0xd0/0x3a4
> > [ 2.453057] really_probe from __driver_probe_device+0x8c/0x1d4
> > [ 2.459014] __driver_probe_device from driver_probe_device+0x30/0xc0
> > [ 2.465493] driver_probe_device from
> > __driver_attach_async_helper+0x50/0xd8
> > [ 2.472580] __driver_attach_async_helper from
> > async_run_entry_fn+0x30/0x144
> > [ 2.479666] async_run_entry_fn from process_one_work+0x154/0x2dc
> > [ 2.485800] process_one_work from worker_thread+0x250/0x3f0
> > [ 2.491494] worker_thread from kthread+0x110/0x12c
> > [ 2.496408] kthread from ret_from_fork+0x14/0x28
> > [ 2.501140] Exception stack(0xe6a0dfb0 to 0xe6a0dff8)
> > [ 2.506214] dfa0: 00000000
> > 00000000 00000000 00000000
> > [ 2.514418] dfc0: 00000000 00000000 00000000 00000000 00000000
> > 00000000 00000000 00000000
> > [ 2.522620] dfe0: 00000000 00000000 00000000 00000000 00000013
> > 00000000
> >
> > This was not the case with kernel v6.11, do you have an idea where this comes
> > from? I did not dig into more detail yet but it looks a bit like a regression. The
> > driver still works, it just prints this duplicate filename warning.
> Hi Stefan:
> I use my i.MX6QP SabreSD board to make a quick boot test when both the
> v6.12-rc2 and v6.12-rc1 are used.
> Since I don't have the i.MX6QDL board at my hand now.
> There is no dump, kernel boots successfully, and PCIe works well too.
> Do I miss something?
> BTW, the imx_v6_v7_defconfig is used in my tests.
>
> root@imx6qpdlsolox:~# lspci
> 00:00.0 PCI bridge: Synopsys, Inc. DWC_usb3 / PCIe bridge (rev 01)
> 01:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
> root@imx6qpdlsolox:~# uname -a
> Linux imx6qpdlsolox 6.12.0-rc2 #11 SMP Sat Oct 12 16:56:57 CST 2024 armv7l GNU/Linux
> root@imx6qpdlsolox:~#
> root@imx6qpdlsolox:~#
> root@imx6qpdlsolox:~# dmesg | grep pci
> [ 0.442344] imx6q-pcie 1ffc000.pcie: host bridge /soc/pcie@1ffc000 ranges:
> [ 0.442397] imx6q-pcie 1ffc000.pcie: IO 0x0001f80000..0x0001f8ffff -> 0x0000000000
> [ 0.442427] imx6q-pcie 1ffc000.pcie: MEM 0x0001000000..0x0001efffff -> 0x0001000000
> [ 1.659104] imx6q-pcie 1ffc000.pcie: iATU: unroll F, 4 ob, 4 ib, align 64K, limit 4G
> [ 1.765277] imx6q-pcie 1ffc000.pcie: PCIe Gen.1 x1 link up
> [ 1.770809] imx6q-pcie 1ffc000.pcie: Link: Only Gen1 is enabled
> [ 1.770820] imx6q-pcie 1ffc000.pcie: Link up, Gen1
> [ 1.784066] imx6q-pcie 1ffc000.pcie: PCIe Gen.1 x1 link up
> [ 1.796446] imx6q-pcie 1ffc000.pcie: PCI host bridge to bus 0000:00
> [ 1.809095] pci_bus 0000:00: root bus resource [bus 00-ff]
> [ 1.809113] pci_bus 0000:00: root bus resource [io 0x0000-0xffff]
> [ 1.809125] pci_bus 0000:00: root bus resource [mem 0x01000000-0x01efffff]
> [ 1.822423] pci 0000:00:00.0: [16c3:abcd] type 01 class 0x060400 PCIe Root Port
> [ 1.822451] pci 0000:00:00.0: BAR 0 [mem 0x00000000-0x000fffff]
> [ 1.834148] pci 0000:00:00.0: ROM [mem 0x00000000-0x0000ffff pref]
> [ 1.849760] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
> [ 1.890183] pci 0000:00:00.0: bridge window [io 0x0000-0x0fff]
> [ 1.896293] pci 0000:00:00.0: bridge window [mem 0x00000000-0x000fffff]
> [ 1.903109] pci 0000:00:00.0: bridge window [mem 0x00000000-0x000fffff pref]
> [ 1.910386] pci 0000:00:00.0: Limiting cfg_size to 512
> [ 1.915588] pci 0000:00:00.0: supports D1
> [ 1.919638] pci 0000:00:00.0: PME# supported from D0 D1 D3hot D3cold
> [ 1.944036] pci 0000:01:00.0: [8086:10d3] type 00 class 0x020000 PCIe Endpoint
> [ 1.951427] pci 0000:01:00.0: BAR 0 [mem 0x00000000-0x0001ffff]
> [ 1.961171] pci 0000:01:00.0: BAR 1 [mem 0x00000000-0x0007ffff]
> [ 1.967149] pci 0000:01:00.0: BAR 2 [io 0x0000-0x001f]
> [ 1.972456] pci 0000:01:00.0: BAR 3 [mem 0x00000000-0x00003fff]
> [ 1.978528] pci 0000:01:00.0: ROM [mem 0x00000000-0x0003ffff pref]
> [ 1.985185] pci 0000:01:00.0: PME# supported from D0 D3hot D3cold
> [ 2.020060] pci 0000:00:00.0: BAR 0 [mem 0x01000000-0x010fffff]: assigned
> [ 2.032893] pci 0000:00:00.0: bridge window [mem 0x01100000-0x011fffff]: assigned
> [ 2.046230] pci 0000:00:00.0: bridge window [mem 0x01200000-0x012fffff pref]: assigned
> [ 2.059918] pci 0000:00:00.0: ROM [mem 0x01300000-0x0130ffff pref]: assigned
> [ 2.072647] pci 0000:00:00.0: bridge window [io 0x1000-0x1fff]: assigned
> [ 2.085371] pci 0000:01:00.0: BAR 1 [mem 0x01100000-0x0117ffff]: assigned
> [ 2.097773] pci 0000:01:00.0: ROM [mem 0x01200000-0x0123ffff pref]: assigned
> [ 2.112229] pci 0000:01:00.0: BAR 0 [mem 0x01180000-0x0119ffff]: assigned
> [ 2.112266] pci 0000:01:00.0: BAR 3 [mem 0x011a0000-0x011a3fff]: assigned
> [ 2.124738] pci 0000:01:00.0: BAR 2 [io 0x1000-0x101f]: assigned
> [ 2.137379] pci 0000:00:00.0: PCI bridge to [bus 01-ff]
> [ 2.149485] pci 0000:00:00.0: bridge window [io 0x1000-0x1fff]
> [ 2.149502] pci 0000:00:00.0: bridge window [mem 0x01100000-0x011fffff]
> [ 2.160835] pci 0000:00:00.0: bridge window [mem 0x01200000-0x012fffff pref]
> [ 2.173722] pci_bus 0000:00: resource 4 [io 0x0000-0xffff]
> [ 2.193124] pci_bus 0000:00: resource 5 [mem 0x01000000-0x01efffff]
> [ 2.193139] pci_bus 0000:01: resource 0 [io 0x1000-0x1fff]
> [ 2.222093] pci_bus 0000:01: resource 1 [mem 0x01100000-0x011fffff]
> [ 2.228389] pci_bus 0000:01: resource 2 [mem 0x01200000-0x012fffff pref]

Thanks a lot for testing on your side.

I think I was too early to assume it is a regression. I did some more
tests today and I can't see the issue with most configurations. I
uploaded the one that generates the issue on my system with kernel
v6.12-rc1.
https://drive.google.com/file/d/1ZHpg6tG82QjmiXylq0W2HSLnz97AgyN8

However, even if I enhance the pci-imx6.c driver with a simple pr_info
the trace disappears:
diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 808d1f1054173..047f4ae0a2ed3 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -1282,6 +1282,8 @@ static int imx_pcie_probe(struct platform_device *pdev)
u16 val;
int i;

+ pr_info("%s - %s:%d\n", __func__, __FILE__, __LINE__);
+
imx_pcie = devm_kzalloc(dev, sizeof(*imx_pcie), GFP_KERNEL);
if (!imx_pcie)
return -ENOMEM;

So most likely it is some sequence/timing issue. I have to check if I
find the time to investigate it further, but I guess it would be on my
side to figure out what happens.

Sorry for the (kind of) false alarm.

Regards,
Stefan