[PATCH V2 3/7] i2c: sprd: Use global variables to record I2C ack/nack status instead of local variables

[Huangzheng Lai]

We found that when the interrupt bit of the I2C controller is cleared,
the ack/nack bit is also cleared at the same time. After clearing the
interrupt bit in sprd_i2c_isr(), incorrect ack/nack information will be
obtained in sprd_i2c_isr_thread(), resulting in incorrect communication
when nack cannot be recognized. To solve this problem, we used a global
variable to record ack/nack information before clearing the interrupt
bit instead of a local variable.

Fixes: 8b9ec0719834 ("i2c: Add Spreadtrum I2C controller driver")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.14+
Signed-off-by: Huangzheng Lai <Huangzheng.Lai@xxxxxxxxxx>
---
 drivers/i2c/busses/i2c-sprd.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
index aa602958d4fd..dec627ef408c 100644
--- a/drivers/i2c/busses/i2c-sprd.c
+++ b/drivers/i2c/busses/i2c-sprd.c
@@ -85,6 +85,7 @@ struct sprd_i2c {
 	struct clk *clk;
 	u32 src_clk;
 	u32 bus_freq;
+	bool ack_flag;
 	struct completion complete;
 	struct reset_control *rst;
 	u8 *buf;
@@ -119,6 +120,7 @@ static void sprd_i2c_clear_ack(struct sprd_i2c *i2c_dev)
 {
 	u32 tmp = readl(i2c_dev->base + I2C_STATUS);
 
+	i2c_dev->ack_flag = 0;
 	writel(tmp & ~I2C_RX_ACK, i2c_dev->base + I2C_STATUS);
 }
 
@@ -393,7 +395,6 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 {
 	struct sprd_i2c *i2c_dev = dev_id;
 	struct i2c_msg *msg = i2c_dev->msg;
-	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
 	u32 i2c_tran;
 
 	if (msg->flags & I2C_M_RD)
@@ -409,7 +410,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 	 * For reading data, ack is always true, if i2c_tran is not 0 which
 	 * means we still need to contine to read data from slave.
 	 */
-	if (i2c_tran && ack) {
+	if (i2c_tran && i2c_dev->ack_flag) {
 		sprd_i2c_data_transfer(i2c_dev);
 		return IRQ_HANDLED;
 	}
@@ -420,7 +421,7 @@ static irqreturn_t sprd_i2c_isr_thread(int irq, void *dev_id)
 	 * If we did not get one ACK from slave when writing data, we should
 	 * return -EIO to notify users.
 	 */
-	if (!ack)
+	if (!i2c_dev->ack_flag)
 		i2c_dev->err = -EIO;
 	else if (msg->flags & I2C_M_RD && i2c_dev->count)
 		sprd_i2c_read_bytes(i2c_dev, i2c_dev->buf, i2c_dev->count);
@@ -437,7 +438,6 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
 {
 	struct sprd_i2c *i2c_dev = dev_id;
 	struct i2c_msg *msg = i2c_dev->msg;
-	bool ack = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
 	u32 i2c_tran;
 
 	if (msg->flags & I2C_M_RD)
@@ -456,7 +456,8 @@ static irqreturn_t sprd_i2c_isr(int irq, void *dev_id)
 	 * means we can read all data in one time, then we can finish this
 	 * transmission too.
 	 */
-	if (!i2c_tran || !ack) {
+	i2c_dev->ack_flag = !(readl(i2c_dev->base + I2C_STATUS) & I2C_RX_ACK);
+	if (!i2c_tran || !i2c_dev->ack_flag) {
 		sprd_i2c_clear_start(i2c_dev);
 		sprd_i2c_clear_irq(i2c_dev);
 	}
-- 
2.17.1