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Subject[PATCH v1 51/63] input: Atmel: limit the max bytes transferred while reading T5 messages
Date
From: Deepak Das <deepak_das@mentor.com>

"a008387 Input: atmel_mxt_ts: Limit the max bytes transferred in an i2c
transaction" limited the Max bytes transferred in i2c transaction while
reading T5 message in mxt_process_messages_until_invalid().

mxt_process_messages_t44() reads the T44 message which contains the
pending T5 message count. If the number of pending T5 messages returned
by T44 message is too high then there is a risk of i2c transaction
timeout while reading T5 messages in mxt_process_messages_t44().

To avoid i2c transaction timeout, this commit limits the max bytes
transferred in a single transaction while reading T5 messages in
mxt_process_messages_t44() depending on the property 'atmel,mtu'.
This improvement is created based on the commit "a008387 Input:
atmel_mxt_ts: Limit the max bytes transferred in an i2c
transaction"

Signed-off-by: Deepak Das <deepak_das@mentor.com>
Signed-off-by: Sanjeev Chugh <sanjeev_chugh@mentor.com>
Signed-off-by: George G. Davis <george_davis@mentor.com>
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
---
drivers/input/touchscreen/atmel_mxt_ts.c | 73 ++++++++++++++----------
1 file changed, 44 insertions(+), 29 deletions(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index 2041a82a4551..47c1e72152de 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -1472,11 +1472,32 @@ static int mxt_read_and_process_messages(struct mxt_data *data, u8 count)
return num_valid;
}

+static u8 mxt_max_msg_read_count(struct mxt_data *data, u8 max_T5_msg_count)
+{
+ u8 T5_msg_count_limit = data->mtu / data->T5_msg_size;
+
+ if (!data->mtu)
+ return max_T5_msg_count;
+
+ 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 maximum number of T5 messages in single i2c transaction
+ * based on "atmel,mtu" property.
+ */
+ return min(T5_msg_count_limit, max_T5_msg_count);
+}
+
static irqreturn_t mxt_process_messages_t44(struct mxt_data *data)
{
struct device *dev = &data->client->dev;
int ret;
- u8 count, num_left;
+ u8 T5_msg_count, total_pending;
+ u8 total_processed = 0;
+ u8 processed_valid = 0;

/* Read T44 and T5 together */
ret = __mxt_read_reg(data->client, data->T44_address,
@@ -1486,18 +1507,19 @@ static irqreturn_t mxt_process_messages_t44(struct mxt_data *data)
return IRQ_NONE;
}

- count = data->msg_buf[0];
+ T5_msg_count = data->msg_buf[0];

/*
* This condition may be caused by the CHG line being configured in
* Mode 0. It results in unnecessary I2C operations but it is benign.
*/
- if (count == 0)
+ if (!T5_msg_count)
return IRQ_NONE;

- if (count > data->max_reportid) {
- dev_warn(dev, "T44 count %d exceeded max report id\n", count);
- count = data->max_reportid;
+ if (T5_msg_count > data->max_reportid) {
+ dev_warn(dev, "T44 count %d exceeded max report id\n",
+ T5_msg_count);
+ T5_msg_count = data->max_reportid;
}

/* Process first message */
@@ -1507,16 +1529,25 @@ static irqreturn_t mxt_process_messages_t44(struct mxt_data *data)
return IRQ_NONE;
}

- num_left = count - 1;
+ total_pending = T5_msg_count - 1;
+ if (!total_pending)
+ goto end;

/* Process remaining messages if necessary */
- if (num_left) {
- ret = mxt_read_and_process_messages(data, num_left);
+ T5_msg_count = mxt_max_msg_read_count(data, total_pending);
+
+ do {
+ if ((total_pending - total_processed) < T5_msg_count)
+ T5_msg_count = total_pending - total_processed;
+ ret = mxt_read_and_process_messages(data, T5_msg_count);
if (ret < 0)
goto end;
- else if (ret != num_left)
- dev_warn(dev, "Unexpected invalid message\n");
- }
+ total_processed += T5_msg_count;
+ processed_valid += ret;
+ } while (total_processed < total_pending);
+
+ if (processed_valid != total_pending)
+ dev_warn(dev, "Unexpected invalid message\n");

end:
if (data->update_input) {
@@ -1527,29 +1558,13 @@ 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;
int tries;

- count = mxt_max_msg_read_count(data);
+ count = mxt_max_msg_read_count(data, data->max_reportid);
tries = (data->max_reportid / count) + 1;

/* Read messages until we force an invalid */
--
2.19.2
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