From: Balasubramani Vivekanandan <balasubramani_vivekanandan@xxxxxxxxxx>
In mxt_process_messages_until_invalid() function, driver tries to read
all possible reportid in a single i2c transaction. Number of bytes read
is limited by the max_reportid parameter.
If the max_reportid is a very large value, then a large chunk of bytes
will be requested from the controller in a single i2c transaction.
This transaction can fail due to timeout. This is visible when the
Atmel controller is connected to the SOC via a i2c mux hardware.
New property 'atmel,mtu' is created. This property limits the maximum
number of bytes that can read/transferred in an i2c transcation
Signed-off-by: Balasubramani Vivekanandan <balasubramani_vivekanandan@xxxxxxxxxx>
Signed-off-by: George G. Davis <george_davis@xxxxxxxxxx>
Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
---
.../bindings/input/atmel,maxtouch.txt | 3 +++
drivers/input/touchscreen/atmel_mxt_ts.c | 26 +++++++++++++++++--
2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/input/atmel,maxtouch.txt b/Documentation/devicetree/bindings/input/atmel,maxtouch.txt
index 7afe12a93202..a7f9a8e551f7 100644
--- a/Documentation/devicetree/bindings/input/atmel,maxtouch.txt
+++ b/Documentation/devicetree/bindings/input/atmel,maxtouch.txt
@@ -45,6 +45,8 @@ Optional properties for main touchpad device:
- atmel,gpios: Specify the GPIO input pins whose status will be read via the
/sys/class/input/input<n>/backlight_error<x> sysfs entries.
+- atmel,mtu: Maximum number of bytes that can read/transferred in an i2c transaction
+
Example:
touch@4b {
@@ -52,6 +54,7 @@ Example:
reg = <0x4b>;
interrupt-parent = <&gpio>;
interrupts = <TEGRA_GPIO(W, 3) IRQ_TYPE_LEVEL_LOW>;
+ atmel,mtu = <200>
atmel,gpios {
backlight_error1 {
diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index c6ba061098c0..e315ad3a8d2a 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -421,6 +421,7 @@ struct mxt_data {
unsigned long gpio_input_pin_status;
struct attribute_group gpio_attrs;
unsigned long gpio_input_pin_status_default;
+ unsigned int mtu;
bool t25_status;
};
@@ -1522,13 +1523,30 @@ static irqreturn_t mxt_process_messages_t44(struct mxt_data *data)
return IRQ_HANDLED;
}
+static u8 mxt_max_msg_read_count(struct mxt_data *data)
+{
+ u8 count_limit = data->mtu / data->T5_msg_size;
+
+ if (!data->mtu)
+ return data->max_reportid;
+
+ if (data->mtu < data->T5_msg_size) {
+ WARN(1, "mtu set is lesser than the T5 message size\n");
+ /* Return count of 1, as fallback */
+ return 1;
+ }
+
+ return min(count_limit, data->max_reportid);
+}
+
static int mxt_process_messages_until_invalid(struct mxt_data *data)
{
struct device *dev = &data->client->dev;
int count, read;
- u8 tries = 2;
+ int tries;
- count = data->max_reportid;
+ count = mxt_max_msg_read_count(data);
+ tries = (data->max_reportid / count) + 1;
/* Read messages until we force an invalid */
do {
@@ -4290,6 +4308,10 @@ static int mxt_parse_device_properties(struct mxt_data *data)
of_node_put(np_gpio);
}
+ device_property_read_u32(dev, "atmel,mtu", &data->mtu);
+ if (data->mtu)
+ dev_dbg(dev, "mtu is set as %d\n", data->mtu);
+
return 0;
err_gpios_property_put:
--
2.19.2
