diff options
Diffstat (limited to 'drivers/i2c/i2c-core-acpi.c')
| -rw-r--r-- | drivers/i2c/i2c-core-acpi.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c index 14ae0cfc325e..d2499f302b50 100644 --- a/drivers/i2c/i2c-core-acpi.c +++ b/drivers/i2c/i2c-core-acpi.c @@ -355,6 +355,25 @@ static const struct acpi_device_id i2c_acpi_force_400khz_device_ids[] = { {} }; +static const struct acpi_device_id i2c_acpi_force_100khz_device_ids[] = { + /* + * When a 400KHz freq is used on this model of ELAN touchpad in Linux, + * excessive smoothing (similar to when the touchpad's firmware detects + * a noisy signal) is sometimes applied. As some devices' (e.g, Lenovo + * V15 G4) ACPI tables specify a 400KHz frequency for this device and + * some I2C busses (e.g, Designware I2C) default to a 400KHz freq, + * force the speed to 100KHz as a workaround. + * + * For future investigation: This problem may be related to the default + * HCNT/LCNT values given by some busses' drivers, because they are not + * specified in the aforementioned devices' ACPI tables, and because + * the device works without issues on Windows at what is expected to be + * a 400KHz frequency. The root cause of the issue is not known. + */ + { "ELAN06FA", 0 }, + {} +}; + static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level, void *data, void **return_value) { @@ -373,6 +392,9 @@ static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level, if (acpi_match_device_ids(adev, i2c_acpi_force_400khz_device_ids) == 0) lookup->force_speed = I2C_MAX_FAST_MODE_FREQ; + if (acpi_match_device_ids(adev, i2c_acpi_force_100khz_device_ids) == 0) + lookup->force_speed = I2C_MAX_STANDARD_MODE_FREQ; + return AE_OK; } |