[PATCH v2] pci: quirks: Disable native PCIe hotplug on MSI Claw A8 root bridge

[PATCH v2] pci: quirks: Disable native PCIe hotplug on MSI Claw A8 root bridge

[Derek J. Clark]

The MSI Claw A8 (MS-1T8K) hard-locks on resume from s2idle whenever an
SD/MMC card is present in the onboard Realtek RTS525A card reader
(10ec:525a), which sits behind root port 0000:00:02.2. The reader's
PCIe endpoint is fixed/soldered and not user-hotpluggable.

Firmware advertises this root port as PCIe hotplug-capable, and _OSC
grants the OS native hotplug control. When native hotplug is OS-owned,
resuming from s2idle races the port's hotplug/PME resume handling
against the RTS525A's own resume sequence when a card is present,
hard-locking the system.

Two kernel command line parameters were confirmed to prevent the hang:
pcie_aspm=off and pcie_ports=compat. Both stop the OS from running
its own hotplug/PME resume path against this port. The former does
so by dropping _OSC negotiation during boot, skipping the path that
enables PCIeHotPlug. The latter prevents the PME service resume
handling by aborting registration of the ports native services. Testing
different kernel boot commands, including pciehp=off and pcie_pme=off
did not resolve the issue. AER, DPC, SHPC, and LTR flags were not tested
because the hardware reports that the platform doesn't support those
features.

This quirk implements as narrow a fix as possible, clearing
is_hotplug_bridge and is_pciehp on the root bridge, scoped by DMI board
name and this root port's bus/device/function, so the port driver never
registers a native hotplug service against it.

SD card insertion is handled entirely by rtsx_pci's own card-detect logic,
so is unaffected by this quirk.

Signed-off-by: Derek J. Clark <derekjohn.clark@gmail.com>
---
v2:
  - Switch to pci_info vice dev_info.
  - use is_hotplug_bridge and is_pciehp on the root port instead of
    native_pcie_hotplug on the root bridge.
v1: https://lore.kernel.org/linux-pci/20260806190439.12022-1-derekjohn.clark@gmail.com/
---
 drivers/pci/quirks.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 6501c949c5b7..62480fe10bcd 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -6420,3 +6420,26 @@ static void pci_mask_replay_timer_timeout(struct pci_dev *pdev)
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9750, pci_mask_replay_timer_timeout);
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_GLI, 0x9755, pci_mask_replay_timer_timeout);
 #endif
+
+/*
+ * The MSI Claw A8 firmware advertises native PCIe hotplug support for
+ * this root port, but native hotplug handling causes resume failures.
+ * Prevent the PCIe port driver from claiming native hotplug ownership
+ * of this port.
+ */
+static void quirk_claw_a8_no_native_hotplug(struct pci_dev *pdev)
+{
+	if (!dmi_match(DMI_BOARD_NAME, "MS-1T8K"))
+		return;
+
+	if (pdev->bus->number != 0 ||
+	    PCI_SLOT(pdev->devfn) != 2 ||
+	    PCI_FUNC(pdev->devfn) != 2)
+		return;
+
+	pci_info(pdev, "disabling native PCIe hotplug\n");
+	pdev->is_hotplug_bridge = 0;
+	pdev->is_pciehp = 0;
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, 0x150b,
+			 quirk_claw_a8_no_native_hotplug);
-- 
2.55.0

Re: [PATCH v2] pci: quirks: Disable native PCIe hotplug on MSI Claw A8 root bridge

[Lukas Wunner]

On Thu, Aug 06, 2026 at 09:48:08PM +0000, Derek J. Clark wrote:
> The MSI Claw A8 (MS-1T8K) hard-locks on resume from s2idle whenever an
> SD/MMC card is present in the onboard Realtek RTS525A card reader
> (10ec:525a), which sits behind root port 0000:00:02.2.

The RTS525A is known to falsely claim that it supports ASPM L0s,
even though it only supports L1.  There is a patch pending to
work around this hardware erratum, I'm wondering whether it
makes the issue go away on the MSI Claw A8?

https://lore.kernel.org/r/20260707021527.639611-1-max.lee@canonical.com/

> The reader's PCIe endpoint is fixed/soldered and not user-hotpluggable.
> Firmware advertises this root port as PCIe hotplug-capable

That looks like an oversight on the part of MSI.  Is there a BIOS update
available which clears the Hot-Plug Capable bit in the Slot Capabilities
Register?  (I'm *assuming* that bit is set -- I haven't seen any dmesg
or lspci -vvv output in your e-mails, perhaps you could open a bug
at bugzilla.kernel.org and upload it there.)

> When native hotplug is OS-owned,
> resuming from s2idle races the port's hotplug/PME resume handling
> against the RTS525A's own resume sequence when a card is present,
> hard-locking the system.

This sounds like a driver bug in rtsx_pci which needs to be root-caused
and fixed, rather than worked around.

pciehp (the OS-native PCIe hotplug driver) normally doesn't de-enumerate
and re-enumerate devices on resume from system sleep.  It uses a heuristic
to determine whether the device in the slot was replaced during system
sleep and synthesizes a hotplug event if it believes there's now a different
device in the slot.  Otherwise it just leaves the device in the slot alone.
The replacement detection is in pciehp_device_replaced(),
drivers/pci/hotplug/pciehp_hpc.c line 567.  You could try hacking
that function to return false and see if it helps.

The heuristic looks at the Vendor ID and Device ID in config space.
I do recall that a different type of card readers, RTS5261, trigger
a hotplug event when a regular UHS card is replaced with an SD Express
card.  The card reader is hot-unplugged and the SD Express card appears
as an NVMe drive with a different Device ID in config space:

https://lore.kernel.org/r/20231016040132.23824-1-kai.heng.feng@canonical.com/

That said, I'm not even sure RTS525A supports SD Express.

What kind of card do you have inserted in the card reader, is it UHS
or SD Express?  Does the issue go away if you eject the card before
going to system sleep?

> +++ b/drivers/pci/quirks.c
[...]
> +/*
> + * The MSI Claw A8 firmware advertises native PCIe hotplug support for
> + * this root port, but native hotplug handling causes resume failures.
> + * Prevent the PCIe port driver from claiming native hotplug ownership
> + * of this port.
> + */
> +static void quirk_claw_a8_no_native_hotplug(struct pci_dev *pdev)
> +{
> +	if (!dmi_match(DMI_BOARD_NAME, "MS-1T8K"))
> +		return;
> +
> +	if (pdev->bus->number != 0 ||
> +	    PCI_SLOT(pdev->devfn) != 2 ||
> +	    PCI_FUNC(pdev->devfn) != 2)
> +		return;
> +
> +	pci_info(pdev, "disabling native PCIe hotplug\n");
> +	pdev->is_hotplug_bridge = 0;
> +	pdev->is_pciehp = 0;
> +}
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, 0x150b,
> +			 quirk_claw_a8_no_native_hotplug);

Unfortunately this is just a workaround that happens to make the
issue disappear, but we'd really want to identify the root cause
first.

If you boot with no_console_suspend, are you able to see any messages
on suspend or resume that could help us understand what is going on?

Thanks,

Lukas

Re: [PATCH v2] pci: quirks: Disable native PCIe hotplug on MSI Claw A8 root bridge

[Derek John Clark]

On Fri, Aug 7, 2026 at 1:53 AM Lukas Wunner <lukas@wunner.de> wrote:
>
> On Thu, Aug 06, 2026 at 09:48:08PM +0000, Derek J. Clark wrote:
> > The MSI Claw A8 (MS-1T8K) hard-locks on resume from s2idle whenever an
> > SD/MMC card is present in the onboard Realtek RTS525A card reader
> > (10ec:525a), which sits behind root port 0000:00:02.2.
>
> The RTS525A is known to falsely claim that it supports ASPM L0s,
> even though it only supports L1.  There is a patch pending to
> work around this hardware erratum, I'm wondering whether it
> makes the issue go away on the MSI Claw A8?
>
> https://lore.kernel.org/r/20260707021527.639611-1-max.lee@canonical.com/
>
Hi Lukas,

Sending again as i inadvertently hit reply instead of reply all.

The freeze still occurs with that patch applied, yes.

> > The reader's PCIe endpoint is fixed/soldered and not user-hotpluggable.
> > Firmware advertises this root port as PCIe hotplug-capable
>
> That looks like an oversight on the part of MSI.  Is there a BIOS update
> available which clears the Hot-Plug Capable bit in the Slot Capabilities
> Register?  (I'm *assuming* that bit is set -- I haven't seen any dmesg
> or lspci -vvv output in your e-mails, perhaps you could open a bug
> at bugzilla.kernel.org and upload it there.)
>

I'm on the latest firmware they have as of abuut a month ago. They
don't participate in LVFS AFAIK but I made sure to update before
switching to Linux.

I posted them here for the entire device tree for the SD card reader:
https://github.com/ValveSoftware/SteamOS/issues/2473#issuecomment-5222972815

> > When native hotplug is OS-owned,
> > resuming from s2idle races the port's hotplug/PME resume handling
> > against the RTS525A's own resume sequence when a card is present,
> > hard-locking the system.
>
> This sounds like a driver bug in rtsx_pci which needs to be root-caused
> and fixed, rather than worked around.
>
> pciehp (the OS-native PCIe hotplug driver) normally doesn't de-enumerate
> and re-enumerate devices on resume from system sleep.  It uses a heuristic
> to determine whether the device in the slot was replaced during system
> sleep and synthesizes a hotplug event if it believes there's now a different
> device in the slot.  Otherwise it just leaves the device in the slot alone.
> The replacement detection is in pciehp_device_replaced(),
> drivers/pci/hotplug/pciehp_hpc.c line 567.  You could try hacking
> that function to return false and see if it helps.
>

That worked! That strikes me as odd since the card is never replaced.

> The heuristic looks at the Vendor ID and Device ID in config space.
> I do recall that a different type of card readers, RTS5261, trigger
> a hotplug event when a regular UHS card is replaced with an SD Express
> card.  The card reader is hot-unplugged and the SD Express card appears
> as an NVMe drive with a different Device ID in config space:
>
> https://lore.kernel.org/r/20231016040132.23824-1-kai.heng.feng@canonical.com/
>
> That said, I'm not even sure RTS525A supports SD Express.
>
> What kind of card do you have inserted in the card reader, is it UHS
> or SD Express?  Does the issue go away if you eject the card before
> going to system sleep?
>

I've been using a SanDisk Ultra 32GB microSDHC UHS-I Card. And yes, it
only happens when the card is present.

> > +++ b/drivers/pci/quirks.c
> [...]
> > +/*
> > + * The MSI Claw A8 firmware advertises native PCIe hotplug support for
> > + * this root port, but native hotplug handling causes resume failures.
> > + * Prevent the PCIe port driver from claiming native hotplug ownership
> > + * of this port.
> > + */
> > +static void quirk_claw_a8_no_native_hotplug(struct pci_dev *pdev)
> > +{
> > +     if (!dmi_match(DMI_BOARD_NAME, "MS-1T8K"))
> > +             return;
> > +
> > +     if (pdev->bus->number != 0 ||
> > +         PCI_SLOT(pdev->devfn) != 2 ||
> > +         PCI_FUNC(pdev->devfn) != 2)
> > +             return;
> > +
> > +     pci_info(pdev, "disabling native PCIe hotplug\n");
> > +     pdev->is_hotplug_bridge = 0;
> > +     pdev->is_pciehp = 0;
> > +}
> > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_AMD, 0x150b,
> > +                      quirk_claw_a8_no_native_hotplug);
>
> Unfortunately this is just a workaround that happens to make the
> issue disappear, but we'd really want to identify the root cause
> first.
>
> If you boot with no_console_suspend, are you able to see any messages
> on suspend or resume that could help us understand what is going on?
>

Nothing of note. After amdgpu finishes its smu resume sequence the
console _ flashes and doesn't progress.

I did try adding some debug printing to pciehp_device_replaced() but
saw no output for that either. Since that didn't work I tried
replacing each true result in the function one at a time and found the
offending case

        if (pdev->hdr_type == PCI_HEADER_TYPE_NORMAL &&
            (pci_read_config_dword(pdev, PCI_SUBSYSTEM_VENDOR_ID, &reg) ||
-            reg != (pdev->subsystem_vendor | (pdev->subsystem_device << 16))))
-               return true;
+            reg != (pdev->subsystem_vendor | (pdev->subsystem_device
<< 16)))) {
+               pci_info(pdev, "pdev subsystem vendor ID mismatch");
+               return false;
+
+       }


[   25.686128] rtsx_pci 0000:c2:00.0: pciehp: pdev subsystem vendor ID mismatch

Any insight on why that might be occurring and what my next
troubleshooting steps should be are appreciated.

** Update: after my initial email & before I sent it back to the
entire ML I did another test and printed the reg vs expected values.
It seems the SD card reader ID is reflected when it is enumerated
during resume.

reg=0x525a10ec expected=0x14af1462

Thanks,

Derek

> Thanks,
>
> Lukas

Re: [PATCH v2] pci: quirks: Disable native PCIe hotplug on MSI Claw A8 root bridge

[Lukas Wunner]

On Fri, Aug 07, 2026 at 05:31:04PM -0700, Derek John Clark wrote:
> [   25.686128] rtsx_pci 0000:c2:00.0: pciehp: pdev subsystem vendor ID mismatch
[...]
> reg=0x525a10ec expected=0x14af1462

The subsystem vendor ID was 0x1462 (MSI) when the card reader was
enumerated on boot and it is 0x10ec (Realtek) on resume.

Likewise the subystem device ID was 0x14af on boot, 0x525a on resume.

It's another bug in the MSI BIOS (in addition to marking the Root Port
hotplug-capable):  The BIOS neglected to re-initialize the subsystem
vendor/device ID registers in config space on resume to the same
values that it set on boot.  The card reader was likely reset while
going through the system sleep transition and its config space
thus needs to be re-initialized.

What happens is that pciehp marks the card reader disconnected
because it assumes that it was replaced during system sleep.
It then synthesizes a Presence Detect Changed event:

https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/pci/hotplug/pciehp_core.c#L300

So the pciehp interrupt thread pciehp_ist() will remove the
rtsx_pci driver and de-enumerate the device.

Replacing or removing PCIe devices during system sleep happens
all the time (e.g. with Thunderbolt) and we haven't seen issues
with regards to that.  The likelihood is higher that the lockup
is caused by rtsx_pci.

Maybe rtsx_pci_remove() blocks somewhere and prevents forward
progress of the resume transition.  In particular, it calls
pm_runtime_get_sync() and cancel_delayed_work_sync(), which are
blocking calls, i.e. they wait for something else to happen.
You could try commenting those calls out and see if it avoids
the lockup:

https://elixir.bootlin.com/linux/v7.2-rc6/source/drivers/misc/cardreader/rtsx_pcr.c#L1608

Another possibility is a crash due to a NULL pointer deref or
GPF somewhere in that driver.  This is pretty difficult to debug
if there's no possibility to see any dmesg output.

Even if we manage to find the root cause of the lockup, as long as
the BIOS isn't fixed, the card reader will always be de-enumerated
and re-enumerated on resume and consequently the card will briefly
disappear.  This will make it impossible to use the card as root
filesystem.

> I've been using a SanDisk Ultra 32GB microSDHC UHS-I Card. And yes, it
> only happens when the card is present.

If you go to sleep and resume without SD card, do you then see in dmesg
that the card reader was de-enumerated and re-enumerated?  Normally
there should be at least a "Card not present" / "Card present" message
from pciehp, if it sensed a replaced device.  ("Card" refers to PCIe card,
not SD card.)

Also, what's the subsystem vendor/device ID as seen with lspci after
a successful system sleep transition (successful = without SD card)?

Thanks,

Lukas