[BUG] HID: i2c-hid: ELAN 04F3:30FD touchpad reset race causes -EREMOTEIO on HP Pavilion Gaming 15-ec1xxx

Hello,

I'm reporting a reproducible probe failure for an ELAN i2c-hid touchpad
(ACPI ELAN0718:00, VID:PID 04F3:30FD) on an HP Pavilion Gaming 15-ec1033nw
(AMD platform, i2c bus under AMDI0010:03). The touchpad fails to
initialize on nearly every boot on Linux, while the same hardware works
reliably every time under Windows 11 on the same machine (dual context,
same BIOS F.35 rev.A).

Kernel: 7.1.6-arch1-1 (Arch Linux)
Also reported by other users with the same touchpad ID on different
kernels/distros (Arch, Ubuntu, Linux Mint) going back to at least 2022:
- https://bbs.archlinux.org/viewtopic.php?id=277393
- https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2031061
- https://forums.linuxmint.com/viewtopic.php?t=329212

Symptom (default logging):

  i2c_hid_acpi i2c-ELAN0718:00: failed to fetch HID descriptor: -121
  i2c_hid_acpi i2c-ELAN0718:00: Failed to fetch the HID Descriptor
  i2c_hid_acpi i2c-ELAN0718:00: probe with driver i2c_hid_acpi failed with
error -121

With dynamic_debug enabled for i2c_hid and i2c_hid_acpi:

  i2c_hid_start_hwreset
  i2c_hid_set_power: cmd=05 00 00 08
  i2c_hid_xfer: cmd=05 00 00 01
  i2c_hid_finish_hwreset: waiting...
  i2c_hid_finish_hwreset: finished.
  asking HID report descriptor
  i2c_hid_xfer: cmd=02 00
  reading report descriptor failed
  can't add hid device: -121
  probe with driver i2c_hid_acpi failed with error -121

Note the device is already tagged with I2C_HID_QUIRK_BOGUS_IRQ and
I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET via the USB_VENDOR_ID_ELAN,
HID_ANY_ID entry in i2c_hid_quirks[], but this specific chip still
appears to need additional settle time between the reset-complete IRQ
and the immediately following descriptor read - the two happen back to
back (sub-millisecond apart in the trace) with zero delay.

The i2c bus and controller are not at fault: an ACPI-level PCI
remove/rescan of the SMBus controller (0000:00:14.0, piix4_smbus)
successfully re-enumerates the bus, and once probe *does* succeed
(intermittently - roughly 1 in 10-15 boots in my testing), the touchpad
works completely normally for the rest of the session. This points to a
narrow timing race rather than a persistent hardware/firmware fault.
Windows never exhibits this behavior on the same machine.

I tested a draft workaround patch (attached) attempting to add msleep()
delays after i2c_hid_finish_hwreset() and before descriptor fetch for
devices with I2C_HID_QUIRK_BOGUS_IRQ, but the issue still persists on my
machine. I am attaching the patch and debug logs in hopes that maintainers
can pinpoint the exact timing, sequence, or quirk needed for this ELAN
revision.

Happy to test alternate patches, adjust delay values, or gather any
additional traces (i2cdump, further dynamic_debug, ACPI tables via
acpidump) if useful.

Hardware:
- HP Pavilion Gaming 15-ec1033nw
- AMD Ryzen 5 4600H
- BIOS F.35 rev.A (latest per HP support site)
- Touchpad: ACPI ELAN0718:00, USB VID:PID 04F3:30FD, on i2c-3 /
  AMDI0010:03

Let me know if you'd like the full dmesg, acpidump, or anything else.

Thanks,
Adam

--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -520,6 +520,18 @@
 	if (!(ihid->quirks & I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET))
 		ret = i2c_hid_set_power(ihid, I2C_HID_PWR_ON);
 
+	/*
+	 * Some ELAN i2c-hid touchpads (e.g. 04F3:30FD, seen on HP Pavilion
+	 * Gaming 15-ec1xxx) signal reset-complete via IRQ before they are
+	 * actually ready to answer the immediately following HID/report
+	 * descriptor read, causing a spurious -EREMOTEIO (-121). The
+	 * Windows driver is known to insert a delay after PWR_ON/RESET
+	 * (see comment in i2c_hid_set_power above); give this quirky class
+	 * of ELAN devices the same grace period.
+	 */
+	if (ihid->quirks & I2C_HID_QUIRK_BOGUS_IRQ)
+		msleep(100);
+
 	return ret;
 }
 
@@ -1052,6 +1064,18 @@
 		return -ENXIO;
 	}
 
+	/*
+	 * Some ELAN i2c-hid touchpads (e.g. 04F3:30FD, seen on HP Pavilion
+	 * Gaming 15-ec1xxx) are not yet ready to answer the very first HID
+	 * descriptor read on cold boot / power-on, before any reset has
+	 * even been issued, causing an intermittent -EREMOTEIO (-121) here.
+	 * Give this quirky class of ELAN devices a short grace period,
+	 * mirroring the delay already applied after hwreset for the same
+	 * quirk further down in this file.
+	 */
+	if (ihid->quirks & I2C_HID_QUIRK_BOGUS_IRQ)
+		msleep(200);
+
 	ret = i2c_hid_fetch_hid_descriptor(ihid);
 	if (ret < 0) {
 		dev_err(&client->dev,