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Subject[PATCH] input: raydium_ts_i2c: Do not split tx transactions
From
Raydium device does not like splitting of tx transactions into
multiple messages - one for the register address and one for the
actual data. This results in incorrect behavior on the device side.

This change updates raydium_i2c_read and raydium_i2c_write to create
i2c_msg arrays separately and passes those arrays into
raydium_i2c_xfer which decides based on the address whether the bank
switch command should be sent. The bank switch header is still added
by raydium_i2c_read and raydium_i2c_write to ensure that all these
operations are performed as part of a single I2C transfer. It
guarantees that no other transactions are initiated to any other
device on the same bus after the bank switch command is sent.

Signed-off-by: Furquan Shaikh <furquan@google.com>
---
drivers/input/touchscreen/raydium_i2c_ts.c | 120 ++++++++++++++-------
1 file changed, 82 insertions(+), 38 deletions(-)

diff --git a/drivers/input/touchscreen/raydium_i2c_ts.c b/drivers/input/touchscreen/raydium_i2c_ts.c
index e694a9b2b1e5..259ecfdf33f1 100644
--- a/drivers/input/touchscreen/raydium_i2c_ts.c
+++ b/drivers/input/touchscreen/raydium_i2c_ts.c
@@ -137,45 +137,25 @@ struct raydium_data {
bool wake_irq_enabled;
};

-static int raydium_i2c_xfer(struct i2c_client *client,
- u32 addr, void *data, size_t len, bool is_read)
-{
- struct raydium_bank_switch_header {
- u8 cmd;
- __be32 be_addr;
- } __packed header = {
- .cmd = RM_CMD_BANK_SWITCH,
- .be_addr = cpu_to_be32(addr),
- };
-
- u8 reg_addr = addr & 0xff;
-
- struct i2c_msg xfer[] = {
- {
- .addr = client->addr,
- .len = sizeof(header),
- .buf = (u8 *)&header,
- },
- {
- .addr = client->addr,
- .len = 1,
- .buf = &reg_addr,
- },
- {
- .addr = client->addr,
- .len = len,
- .buf = data,
- .flags = is_read ? I2C_M_RD : 0,
- }
- };
+/*
+ * Header to be sent for RM_CMD_BANK_SWITCH command. This is used by
+ * raydium_i2c_{read|send} below.
+ */
+struct __packed raydium_bank_switch_header {
+ u8 cmd;
+ __be32 be_addr;
+};

+static int raydium_i2c_xfer(struct i2c_client *client, u32 addr,
+ struct i2c_msg *xfer, size_t xfer_count)
+{
+ int ret;
/*
* If address is greater than 255, then RM_CMD_BANK_SWITCH needs to be
* sent first. Else, skip the header i.e. xfer[0].
*/
int xfer_start_idx = (addr > 0xff) ? 0 : 1;
- size_t xfer_count = ARRAY_SIZE(xfer) - xfer_start_idx;
- int ret;
+ xfer_count -= xfer_start_idx;

ret = i2c_transfer(client->adapter, &xfer[xfer_start_idx], xfer_count);
if (likely(ret == xfer_count))
@@ -189,10 +169,43 @@ static int raydium_i2c_send(struct i2c_client *client,
{
int tries = 0;
int error;
+ u8 *tx_buf;
+ u8 reg_addr = addr & 0xff;
+
+ tx_buf = kmalloc(len + 1, GFP_KERNEL);
+ if (!tx_buf)
+ return -ENOMEM;
+
+ tx_buf[0] = reg_addr;
+ memcpy(tx_buf + 1, data, len);

do {
- error = raydium_i2c_xfer(client, addr, (void *)data, len,
- false);
+ struct raydium_bank_switch_header header = {
+ .cmd = RM_CMD_BANK_SWITCH,
+ .be_addr = cpu_to_be32(addr),
+ };
+
+ /*
+ * Perform as a single i2c_transfer transaction to ensure that
+ * no other I2C transactions are initiated on the bus to any
+ * other device in between. Initiating transacations to other
+ * devices after RM_CMD_BANK_SWITCH is sent is known to cause
+ * issues.
+ */
+ struct i2c_msg xfer[] = {
+ {
+ .addr = client->addr,
+ .len = sizeof(header),
+ .buf = (u8 *)&header,
+ },
+ {
+ .addr = client->addr,
+ .len = len + 1,
+ .buf = tx_buf,
+ },
+ };
+
+ error = raydium_i2c_xfer(client, addr, xfer, ARRAY_SIZE(xfer));
if (likely(!error))
return 0;

@@ -206,12 +219,43 @@ static int raydium_i2c_send(struct i2c_client *client,
static int raydium_i2c_read(struct i2c_client *client,
u32 addr, void *data, size_t len)
{
- size_t xfer_len;
int error;

while (len) {
- xfer_len = min_t(size_t, len, RM_MAX_READ_SIZE);
- error = raydium_i2c_xfer(client, addr, data, xfer_len, true);
+ u8 reg_addr = addr & 0xff;
+ struct raydium_bank_switch_header header = {
+ .cmd = RM_CMD_BANK_SWITCH,
+ .be_addr = cpu_to_be32(addr),
+ };
+ size_t xfer_len = min_t(size_t, len, RM_MAX_READ_SIZE);
+
+ /*
+ * Perform as a single i2c_transfer transaction to ensure that
+ * no other I2C transactions are initiated on the bus to any
+ * other device in between. Initiating transacations to other
+ * devices after RM_CMD_BANK_SWITCH is sent is known to cause
+ * issues.
+ */
+ struct i2c_msg xfer[] = {
+ {
+ .addr = client->addr,
+ .len = sizeof(header),
+ .buf = (u8 *)&header,
+ },
+ {
+ .addr = client->addr,
+ .len = 1,
+ .buf = &reg_addr,
+ },
+ {
+ .addr = client->addr,
+ .len = xfer_len,
+ .buf = data,
+ .flags = I2C_M_RD,
+ }
+ };
+
+ error = raydium_i2c_xfer(client, addr, xfer, ARRAY_SIZE(xfer));
if (unlikely(error))
return error;

--
2.29.2.454.gaff20da3a2-goog
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