Before this commit i2c_hid_parse() consists of the following steps: 1. Send power on cmd 2. usleep_range(1000, 5000) 3. Send reset cmd 4. Wait for reset to complete (device interrupt, or msleep(100)) 5. Send power on cmd 6. Try to read HID descriptor Notice how there is an usleep_range(1000, 5000) after the first power-on command, but not after the second power-on command. Testing has shown that at least on the BMAX Y13 laptop's i2c-hid touchpad, not having a delay after the second power-on command causes the HID descriptor to read as all zeros. In case we hit this on other devices too, the descriptor being all zeros can be recognized by the following message being logged many, many times: hid-generic 0018:0911:5288.0002: unknown main item tag 0x0 Having 2 cases where we need a delay after sending the power-on command, seems to indicate that we should always sleep after the power-on command. So this commit fixes the all zeros HID descriptor issue by moving the existing usleep_range(1000, 5000) to the i2c_hid_set_power() function. Cc: stable@xxxxxxxxxxxxxxx BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=208247 Reported-and-tested-by: Andrea Borgia <andrea@xxxxxxxxxxxx> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- drivers/hid/i2c-hid/i2c-hid-core.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c index 294c84e136d7..e5d7aaf39b5e 100644 --- a/drivers/hid/i2c-hid/i2c-hid-core.c +++ b/drivers/hid/i2c-hid/i2c-hid-core.c @@ -420,6 +420,17 @@ static int i2c_hid_set_power(struct i2c_client *client, int power_state) dev_err(&client->dev, "failed to change power setting.\n"); set_pwr_exit: + + /* + * The HID over I2C specification states that if a DEVICE needs time + * after the PWR_ON request, it should utilise CLOCK stretching. + * However, it has been observered that the Windows driver provides a + * 1ms sleep between the PWR_ON and RESET requests and that some devices + * rely on having a short delay after PWR_ON commands. + */ + if (power_state == I2C_HID_PWR_ON) + usleep_range(1000, 5000); + return ret; } @@ -441,15 +452,6 @@ static int i2c_hid_hwreset(struct i2c_client *client) if (ret) goto out_unlock; - /* - * The HID over I2C specification states that if a DEVICE needs time - * after the PWR_ON request, it should utilise CLOCK stretching. - * However, it has been observered that the Windows driver provides a - * 1ms sleep between the PWR_ON and RESET requests and that some devices - * rely on this. - */ - usleep_range(1000, 5000); - i2c_hid_dbg(ihid, "resetting...\n"); ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0); -- 2.26.2
