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[2/3] HID: i2c-hid: Retry HID descriptor read to wake up STM devices

Message ID 20240415170517.18780-3-kl@kl.wtf
State New
Headers show
Series HID: i2c-hid: Probe and wake device with HID descriptor fetch | expand

Commit Message

Kenny Levinsen April 15, 2024, 5:04 p.m. UTC 
Some STM microcontrollers need some time after rising clock edge in
order to come out of their deep sleep state. This in turn means that the
first command send to them timeout and fail with EREMOTEIO.

Retry once on EREMOTEIO to see if the device came alive, otherwise treat
the error as if no device was present like before.

Link: https://lore.kernel.org/all/20240405102436.3479210-1-lma@chromium.org/#t
Signed-off-by: Kenny Levinsen <kl@kl.wtf>
---
 drivers/hid/i2c-hid/i2c-hid-core.c | 8 ++++++++
 1 file changed, 8 insertions(+)
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Patch

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index 515a80dbf6c7..ac661199d2c8 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -1010,7 +1010,15 @@  static int __i2c_hid_core_probe(struct i2c_hid *ihid)
 	struct hid_device *hid = ihid->hid;
 	int ret;
 
+	/*
+	 * Some STM-based devices need some time after a rising clock edge to
+	 * wake from deep sleep, which in turn means that our first command
+	 * will fail EREMOTEIO. Retry the command in this case.
+	 */
 	ret = i2c_hid_fetch_hid_descriptor(ihid);
+	if (ret == -EREMOTEIO)
+		ret = i2c_hid_fetch_hid_descriptor(ihid);
+
 	if (ret == -EREMOTEIO) {
 		i2c_hid_dbg(ihid, "nothing at this address: %d\n", ret);
 		return -ENXIO;