[PATCH 1/2] HID: i2c-hid: Retry address probe after delay

[Kenny Levinsen <kl@kl.wtf>]

Some STM microcontrollers need 400µs after rising clock edge in order to
come out of their deep sleep state. This in turn means that our address
probe will fail as the device is not ready to service it.

Retry the probe once after a delay to see if the device came alive,
otherwise treat the device as missing.

Link: https://lore.kernel.org/all/20240405102436.3479210-1-lma@chromium.org/#t
Co-developed-by: Radoslaw Biernacki <rad@chromium.org>
Co-developed-by: Lukasz Majczak <lma@chromium.org>
Signed-off-by: Kenny Levinsen <kl@kl.wtf>
---
 drivers/hid/i2c-hid/i2c-hid-core.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index d965382196c6..a40489bb7643 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -163,6 +163,24 @@ static u32 i2c_hid_lookup_quirk(const u16 idVendor, const u16 idProduct)
 	return quirks;
 }
 
+static int i2c_hid_probe_address(struct i2c_hid *ihid)
+{
+	int ret;
+
+	/*
+	 * Some STM-based devices need 400µs after a rising clock edge to wake
+	 * from deep sleep, in which case the first read will fail. Try after a
+	 * short sleep to see if the device came alive on the bus. Certain
+	 * Weida Tech devices also need this.
+	 */
+	ret = i2c_smbus_read_byte(ihid->client);
+	if (ret < 0) {
+		usleep_range(400, 500);
+		ret = i2c_smbus_read_byte(ihid->client);
+	}
+	return ret < 0 ? ret : 0;
+}
+
 static int i2c_hid_xfer(struct i2c_hid *ihid,
 			u8 *send_buf, int send_len, u8 *recv_buf, int recv_len)
 {
@@ -992,8 +1010,7 @@ static int __i2c_hid_core_probe(struct i2c_hid *ihid)
 	struct hid_device *hid = ihid->hid;
 	int ret;
 
-	/* Make sure there is something at this address */
-	ret = i2c_smbus_read_byte(client);
+	ret = i2c_hid_probe_address(ihid);
 	if (ret < 0) {
 		i2c_hid_dbg(ihid, "nothing at this address: %d\n", ret);
 		return -ENXIO;
-- 
2.44.0