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Subject[PATCHv2 1/3] i2c: xlp9xx: Check for Bus state before every transfer
Date
I2C bus enters the STOP condition after the DATA_DONE interrupt is raised.
Essentially the driver should be checking the bus state before sending
any transaction. In case a transaction is initiated while the
bus is busy, the prior transaction's stop condition is not achieved.
Add the check to make sure the bus is not busy before every transaction.

Signed-off-by: George Cherian <george.cherian@cavium.com>
---
drivers/i2c/busses/i2c-xlp9xx.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/drivers/i2c/busses/i2c-xlp9xx.c b/drivers/i2c/busses/i2c-xlp9xx.c
index 1f6d780..42dd1fa 100644
--- a/drivers/i2c/busses/i2c-xlp9xx.c
+++ b/drivers/i2c/busses/i2c-xlp9xx.c
@@ -16,6 +16,7 @@
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/platform_device.h>
+#include <linux/delay.h>

#define XLP9XX_I2C_DIV 0x0
#define XLP9XX_I2C_CTRL 0x1
@@ -36,6 +37,8 @@
#define XLP9XX_I2C_TIMEOUT 0X10
#define XLP9XX_I2C_GENCALLADDR 0x11

+#define XLP9XX_I2C_STATUS_BUSY BIT(0)
+
#define XLP9XX_I2C_CMD_START BIT(7)
#define XLP9XX_I2C_CMD_STOP BIT(6)
#define XLP9XX_I2C_CMD_READ BIT(5)
@@ -71,6 +74,7 @@
#define XLP9XX_I2C_HIGH_FREQ 400000
#define XLP9XX_I2C_FIFO_SIZE 0x80U
#define XLP9XX_I2C_TIMEOUT_MS 1000
+#define XLP9XX_I2C_BUSY_TIMEOUT 50

#define XLP9XX_I2C_FIFO_WCNT_MASK 0xff
#define XLP9XX_I2C_STATUS_ERRMASK (XLP9XX_I2C_INTEN_ARLOST | \
@@ -241,6 +245,26 @@ static irqreturn_t xlp9xx_i2c_isr(int irq, void *dev_id)
return IRQ_HANDLED;
}

+static int xlp9xx_i2c_check_bus_status(struct xlp9xx_i2c_dev *priv)
+{
+ u32 status;
+ u32 busy_timeout = XLP9XX_I2C_BUSY_TIMEOUT;
+
+ while (busy_timeout) {
+ status = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_STATUS);
+ if ((status & XLP9XX_I2C_STATUS_BUSY) == 0)
+ break;
+
+ busy_timeout--;
+ usleep_range(1000, 1100);
+ }
+
+ if (!busy_timeout)
+ return -EIO;
+
+ return 0;
+}
+
static int xlp9xx_i2c_init(struct xlp9xx_i2c_dev *priv)
{
u32 prescale;
@@ -363,6 +387,14 @@ static int xlp9xx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int i, ret;
struct xlp9xx_i2c_dev *priv = i2c_get_adapdata(adap);

+ ret = xlp9xx_i2c_check_bus_status(priv);
+ if (ret) {
+ xlp9xx_i2c_init(priv);
+ ret = xlp9xx_i2c_check_bus_status(priv);
+ if (ret)
+ return ret;
+ }
+
for (i = 0; i < num; i++) {
ret = xlp9xx_i2c_xfer_msg(priv, &msgs[i], i == num - 1);
if (ret != 0)
--
2.1.4
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