Input: ili210x - use resolution from ili251x firmware

The ili251x firmware protocol permits readout of panel resolution,
implement this, but make it possible to override this value using
DT bindings. This way, older DTs which contain touchscreen-size-x
and touchscreen-size-y properties will behave just like before and
new DTs may avoid specifying these for ILI251x.

Note that the command format is different on other controllers, so
this functionality is isolated to ILI251x.
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20210831202506.181927-1-marex@denx.deSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/ili210x.c

@@ -35,6 +35,7 @@ struct ili2xxx_chip {
 	unsigned int max_touches;
 	unsigned int resolution;
 	bool has_calibrate_reg;
+	bool has_firmware_proto;
 	bool has_pressure_reg;
 };
 
@@ -268,6 +269,7 @@ static const struct ili2xxx_chip ili251x_chip = {
 	.continue_polling	= ili251x_check_continue_polling,
 	.max_touches		= 10,
 	.has_calibrate_reg	= true,
+	.has_firmware_proto	= true,
 	.has_pressure_reg	= true,
 };
 
@@ -323,6 +325,54 @@ static irqreturn_t ili210x_irq(int irq, void *irq_data)
 	return IRQ_HANDLED;
 }
 
+static int ili251x_firmware_update_resolution(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ili210x *priv = i2c_get_clientdata(client);
+	u16 resx, resy;
+	u8 rs[10];
+	int error;
+
+	/* The firmware update blob might have changed the resolution. */
+	error = priv->chip->read_reg(client, REG_PANEL_INFO, &rs, sizeof(rs));
+	if (error)
+		return error;
+
+	resx = le16_to_cpup((__le16 *)rs);
+	resy = le16_to_cpup((__le16 *)(rs + 2));
+
+	/* The value reported by the firmware is invalid. */
+	if (!resx || resx == 0xffff || !resy || resy == 0xffff)
+		return -EINVAL;
+
+	input_abs_set_max(priv->input, ABS_X, resx - 1);
+	input_abs_set_max(priv->input, ABS_Y, resy - 1);
+	input_abs_set_max(priv->input, ABS_MT_POSITION_X, resx - 1);
+	input_abs_set_max(priv->input, ABS_MT_POSITION_Y, resy - 1);
+
+	return 0;
+}
+
+static int ili251x_firmware_update_cached_state(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct ili210x *priv = i2c_get_clientdata(client);
+	int error;
+
+	if (!priv->chip->has_firmware_proto)
+		return 0;
+
+	/* Wait for firmware to boot and stabilize itself. */
+	msleep(200);
+
+	/* Firmware does report valid information. */
+	error = ili251x_firmware_update_resolution(dev);
+	if (error)
+		return error;
+
+	return 0;
+}
+
 static ssize_t ili210x_calibrate(struct device *dev,
 				 struct device_attribute *attr,
 				 const char *buf, size_t count)
@@ -449,6 +499,12 @@ static int ili210x_i2c_probe(struct i2c_client *client,
 	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, max_xy, 0, 0);
 	if (priv->chip->has_pressure_reg)
 		input_set_abs_params(input, ABS_MT_PRESSURE, 0, 0xa, 0, 0);
+	error = ili251x_firmware_update_cached_state(dev);
+	if (error) {
+		dev_err(dev, "Unable to cache firmware information, err: %d\n",
+			error);
+		return error;
+	}
 	touchscreen_parse_properties(input, true, &priv->prop);
 
 	error = input_mt_init_slots(input, priv->chip->max_touches,