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Subject[PATCH V1 2/2] i2c: tegra: support for I2C_M_NOSTART protocol mangling
Date
Adding support for protocol mangling I2C_M_NOSTART.
When multiple message transfer request made through i2c
and if any message is flagged with I2C_M_NOSTART then
it will not send the start/repeat start/address of that
message i.e. send the data directly.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
---
drivers/i2c/busses/i2c-tegra.c | 32 +++++++++++++++++++++++++++-----
1 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 18067b3..a50e4c4 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -97,8 +97,21 @@
#define I2C_HEADER_10BIT_ADDR (1<<18)
#define I2C_HEADER_IE_ENABLE (1<<17)
#define I2C_HEADER_REPEAT_START (1<<16)
+#define I2C_HEADER_CONTINUE_XFER (1<<15)
#define I2C_HEADER_MASTER_ADDR_SHIFT 12
#define I2C_HEADER_SLAVE_ADDR_SHIFT 1
+/*
+ * msg_end_type: The bus control which need to be send at end of transfer.
+ * @MSG_END_STOP: Send stop pulse at end of transfer.
+ * @MSG_END_REPEAT_START: Send repeat start at end of transfer.
+ * @MSG_END_CONTINUE: The following on message is coming and so do not send
+ * stop or repeat start.
+ */
+enum msg_end_type {
+ MSG_END_STOP,
+ MSG_END_REPEAT_START,
+ MSG_END_CONTINUE,
+};

/**
* struct tegra_i2c_dev - per device i2c context
@@ -450,7 +463,7 @@ err:
}

static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
- struct i2c_msg *msg, int stop)
+ struct i2c_msg *msg, enum msg_end_type end_state)
{
u32 packet_header;
u32 int_mask;
@@ -477,7 +490,9 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
i2c_writel(i2c_dev, packet_header, I2C_TX_FIFO);

packet_header = I2C_HEADER_IE_ENABLE;
- if (!stop)
+ if (end_state == MSG_END_CONTINUE)
+ packet_header |= I2C_HEADER_CONTINUE_XFER;
+ else if (end_state == MSG_END_REPEAT_START)
packet_header |= I2C_HEADER_REPEAT_START;
if (msg->flags & I2C_M_TEN) {
packet_header |= msg->addr;
@@ -549,8 +564,14 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],

clk_enable(i2c_dev->clk);
for (i = 0; i < num; i++) {
- int stop = (i == (num - 1)) ? 1 : 0;
- ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], stop);
+ enum msg_end_type end_type = MSG_END_STOP;
+ if (i < (num - 1)) {
+ if (msgs[i + 1].flags & I2C_M_NOSTART)
+ end_type = MSG_END_CONTINUE;
+ else
+ end_type = MSG_END_REPEAT_START;
+ }
+ ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], end_type);
if (ret)
break;
}
@@ -560,7 +581,8 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],

static u32 tegra_i2c_func(struct i2c_adapter *adap)
{
- return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR;
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
+ I2C_FUNC_PROTOCOL_MANGLING;
}

static const struct i2c_algorithm tegra_i2c_algo = {
--
1.7.1.1


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