+Jarkko
On Mon, Nov 11, 2019 at 11:48:27AM +0100, Hans de Goede wrote:
> Many cheap devices use Silead touchscreen controllers. Testing has shown
> repeatedly that these touchscreen controllers work fine at 400KHz, but for
> unknown reasons do not work properly at 100KHz. This has been seen on
> both ARM and x86 devices using totally different i2c controllers.
>
> On some devices the ACPI tables list another device at the same I2C-bus
> as only being capable of 100KHz, testing has shown that these other
> devices work fine at 400KHz (as can be expected of any recent I2C hw).
>
> This commit makes i2c_acpi_find_bus_speed() always return 400KHz if a
> Silead touchscreen controller is present, fixing the touchscreen not
> working on devices which ACPI tables' wrongly list another device on the
> same bus as only being capable of 100KHz.
>
> Specifically this fixes the touchscreen on the Jumper EZpad 6 m4 not
> working.
>
> Reported-and-tested-by: youling 257 <youling257@xxxxxxxxx>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> drivers/i2c/i2c-core-acpi.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
> index 9cb2aa1e20ef..420c356eba06 100644
> --- a/drivers/i2c/i2c-core-acpi.c
> +++ b/drivers/i2c/i2c-core-acpi.c
> @@ -39,6 +39,7 @@ struct i2c_acpi_lookup {
> int index;
> u32 speed;
> u32 min_speed;
> + u32 force_speed;
> };
>
> /**
> @@ -285,6 +286,19 @@ i2c_acpi_match_device(const struct acpi_device_id *matches,
> return acpi_match_device(matches, &client->dev);
> }
>
> +static const struct acpi_device_id i2c_acpi_force_400khz_device_ids[] = {
> + /*
> + * These Silead touchscreen controllers only work at 400KHz, for
> + * some reason they do not work at 100KHz. On some devices the ACPI
> + * tables list another device at their bus as only being capable
> + * of 100KHz, testing has shown that these other devices work fine
> + * at 400KHz (as can be expected of any recent i2c hw) so we force
> + * the speed of the bus to 400 KHz if a Silead device is present.
> + */
> + { "MSSL1680", 0 },
> + {}
> +};
> +
> static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level,
> void *data, void **return_value)
> {
> @@ -303,6 +317,9 @@ static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level,
> if (lookup->speed <= lookup->min_speed)
> lookup->min_speed = lookup->speed;
>
> + if (acpi_match_device_ids(adev, i2c_acpi_force_400khz_device_ids) == 0)
> + lookup->force_speed = 400000;
I wonder if it makes sense to log a warning about this? So when
debugging it can be clearly seen from the logs that the device is
quirked.
> +
> return AE_OK;
> }
>
> @@ -340,7 +357,12 @@ u32 i2c_acpi_find_bus_speed(struct device *dev)
> return 0;
> }
>
> - return lookup.min_speed != UINT_MAX ? lookup.min_speed : 0;
> + if (lookup.force_speed)
> + return lookup.force_speed;
> + else if (lookup.min_speed != UINT_MAX)
> + return lookup.min_speed;
> + else
> + return 0;
> }
> EXPORT_SYMBOL_GPL(i2c_acpi_find_bus_speed);
>
> --
> 2.23.0
