[PATCH 0/2] Mediatek I2C driver fixup

[PATCH 0/2] Mediatek I2C driver fixup

[Liguo Zhang]

This series contain two patches, first is to optimize Mediatek I2C driver to use WRRD
if hardware support auto restart. Because auto restart will issue auto restart
interrupt, change to use WRRD can reduce interrupt latency. The second is to fix
multi transfer error in high speed mode. If hardware support auto restart, need driver
to send master code first.

Liguo Zhang (2):
  i2c: mediatek: add i2c first write then read optimization
  i2c: mediatek: fix i2c multi transfer issue in high speed mode

 drivers/i2c/busses/i2c-mt65xx.c | 77 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 71 insertions(+), 6 deletions(-)

--
1.8.1.1.dirty

[PATCH 1/2] i2c: mediatek: add i2c first write then read optimization

[Liguo Zhang]

For platform with auto restart support, between every transfer,
i2c controller will trigger an interrupt and SW need to handle
it to start new transfer. When doing write-then-read transfer,
instead of restart mechanism, using WRRD mode to have controller
send both transfer in one request to reduce latency.

Signed-off-by: Liguo Zhang <liguo.zhang@mediatek.com>
---
 drivers/i2c/busses/i2c-mt65xx.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index 9b86716..dc4aac6 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -132,6 +132,7 @@ struct mtk_i2c_compatible {
 	unsigned char pmic_i2c: 1;
 	unsigned char dcm: 1;
 	unsigned char auto_restart: 1;
+	unsigned char aux_len_reg: 1;
 };
 
 struct mtk_i2c {
@@ -153,6 +154,7 @@ struct mtk_i2c {
 	enum mtk_trans_op op;
 	u16 timing_reg;
 	u16 high_speed_reg;
+	unsigned char auto_restart;
 	const struct mtk_i2c_compatible *dev_comp;
 };
 
@@ -178,6 +180,7 @@ static const struct mtk_i2c_compatible mt6577_compat = {
 	.pmic_i2c = 0,
 	.dcm = 1,
 	.auto_restart = 0,
+	.aux_len_reg = 0,
 };
 
 static const struct mtk_i2c_compatible mt6589_compat = {
@@ -185,6 +188,7 @@ static const struct mtk_i2c_compatible mt6589_compat = {
 	.pmic_i2c = 1,
 	.dcm = 0,
 	.auto_restart = 0,
+	.aux_len_reg = 0,
 };
 
 static const struct mtk_i2c_compatible mt8173_compat = {
@@ -192,6 +196,7 @@ static const struct mtk_i2c_compatible mt8173_compat = {
 	.pmic_i2c = 0,
 	.dcm = 1,
 	.auto_restart = 1,
+	.aux_len_reg = 1,
 };
 
 static const struct of_device_id mtk_i2c_of_match[] = {
@@ -373,7 +378,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 
 	i2c->irq_stat = 0;
 
-	if (i2c->dev_comp->auto_restart)
+	if (i2c->auto_restart)
 		restart_flag = I2C_RS_TRANSFER;
 
 	reinit_completion(&i2c->msg_complete);
@@ -411,8 +416,14 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 
 	/* Set transfer and transaction len */
 	if (i2c->op == I2C_MASTER_WRRD) {
-		writew(msgs->len | ((msgs + 1)->len) << 8,
-		       i2c->base + OFFSET_TRANSFER_LEN);
+		if (i2c->dev_comp->aux_len_reg) {
+			writew(msgs->len, i2c->base + OFFSET_TRANSFER_LEN);
+			writew((msgs + 1)->len, i2c->base +
+			       OFFSET_TRANSFER_LEN_AUX);
+		} else {
+			writew(msgs->len | ((msgs + 1)->len) << 8,
+			       i2c->base + OFFSET_TRANSFER_LEN);
+		}
 		writew(I2C_WRRD_TRANAC_VALUE, i2c->base + OFFSET_TRANSAC_LEN);
 	} else {
 		writew(msgs->len, i2c->base + OFFSET_TRANSFER_LEN);
@@ -461,7 +472,7 @@ static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 
 	writel(I2C_DMA_START_EN, i2c->pdmabase + OFFSET_EN);
 
-	if (!i2c->dev_comp->auto_restart) {
+	if (!i2c->auto_restart) {
 		start_reg = I2C_TRANSAC_START;
 	} else {
 		start_reg = I2C_TRANSAC_START | I2C_RS_MUL_TRIG;
@@ -518,6 +529,16 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
 	if (ret)
 		return ret;
 
+	i2c->auto_restart = i2c->dev_comp->auto_restart;
+
+	/* checking if we can skip restart and optimize using WRRD mode */
+	if (i2c->auto_restart && num == 2) {
+		if (!(msgs[0].flags & I2C_M_RD) && (msgs[1].flags & I2C_M_RD) &&
+		    msgs[0].addr == msgs[1].addr) {
+			i2c->auto_restart = 0;
+		}
+	}
+
 	while (left_num--) {
 		if (!msgs->buf) {
 			dev_dbg(i2c->dev, "data buffer is NULL.\n");
@@ -530,7 +551,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
 		else
 			i2c->op = I2C_MASTER_WR;
 
-		if (!i2c->dev_comp->auto_restart) {
+		if (!i2c->auto_restart) {
 			if (num > 1) {
 				/* combined two messages into one transaction */
 				i2c->op = I2C_MASTER_WRRD;
@@ -559,7 +580,7 @@ static irqreturn_t mtk_i2c_irq(int irqno, void *dev_id)
 	u16 restart_flag = 0;
 	u16 intr_stat;
 
-	if (i2c->dev_comp->auto_restart)
+	if (i2c->auto_restart)
 		restart_flag = I2C_RS_TRANSFER;
 
 	intr_stat = readw(i2c->base + OFFSET_INTR_STAT);
-- 
1.8.1.1.dirty

[PATCH 2/2] i2c: mediatek: fix i2c multi transfer issue in high speed mode

[Liguo Zhang]

For platform with auto restart support, when doing i2c multi transfer
in high speed, for example, doing write-then-read transfer, the master
code will occupy the first transfer, and the second transfer will be
the read transfer, the write transfer will be discarded. So we should
first send the master code, and then start i2c multi transfer.

Signed-off-by: Liguo Zhang <liguo.zhang@mediatek.com>
---
 drivers/i2c/busses/i2c-mt65xx.c | 44 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index dc4aac6..0b9e9f5 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -53,6 +53,8 @@
 #define I2C_FS_TIME_INIT_VALUE		0x1303
 #define I2C_WRRD_TRANAC_VALUE		0x0002
 #define I2C_RD_TRANAC_VALUE		0x0001
+#define I2C_TRAN_DEFAULT_VALUE		0x0001
+#define I2C_TRANAC_DEFAULT_VALUE	0x0001
 
 #define I2C_DMA_CON_TX			0x0000
 #define I2C_DMA_CON_RX			0x0001
@@ -365,6 +367,42 @@ static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int parent_clk,
 	return 0;
 }
 
+static int mtk_i2c_send_master_code(struct mtk_i2c *i2c)
+{
+	int ret = 0;
+
+	reinit_completion(&i2c->msg_complete);
+
+	writew(I2C_CONTROL_RS | I2C_CONTROL_ACKERR_DET_EN |
+	       I2C_CONTROL_CLK_EXT_EN | I2C_CONTROL_DMA_EN,
+	       i2c->base + OFFSET_CONTROL);
+
+	/* Clear interrupt status */
+	writew(I2C_RS_TRANSFER | I2C_TRANSAC_COMP | I2C_HS_NACKERR | I2C_ACKERR,
+	       i2c->base + OFFSET_INTR_STAT);
+
+	/* Enable interrupt */
+	writew(I2C_RS_TRANSFER | I2C_TRANSAC_COMP, i2c->base + OFFSET_INTR_MASK);
+
+	writew(I2C_TRAN_DEFAULT_VALUE, i2c->base + OFFSET_TRANSFER_LEN);
+	writew(I2C_TRANAC_DEFAULT_VALUE, i2c->base + OFFSET_TRANSAC_LEN);
+
+	writew(I2C_TRANSAC_START | I2C_RS_MUL_CNFG, i2c->base + OFFSET_START);
+
+	ret = wait_for_completion_timeout(&i2c->msg_complete,
+					  i2c->adap.timeout);
+
+	completion_done(&i2c->msg_complete);
+
+	if (ret == 0) {
+		dev_dbg(i2c->dev, "send master code timeout.\n");
+		mtk_i2c_init_hw(i2c);
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
 static int mtk_i2c_do_transfer(struct mtk_i2c *i2c, struct i2c_msg *msgs,
 			       int num, int left_num)
 {
@@ -539,6 +577,12 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
 		}
 	}
 
+	if (i2c->auto_restart && i2c->speed_hz > 400000) {
+		ret = mtk_i2c_send_master_code(i2c);
+		if (ret)
+			return ret;
+	}
+
 	while (left_num--) {
 		if (!msgs->buf) {
 			dev_dbg(i2c->dev, "data buffer is NULL.\n");
-- 
1.8.1.1.dirty

Re: [PATCH 0/2] Mediatek I2C driver fixup

[Eddie Huang]

On Tue, 2015-10-27 at 16:59 +0800, Liguo Zhang wrote:
> This series contain two patches, first is to optimize Mediatek I2C driver to use WRRD
> if hardware support auto restart. Because auto restart will issue auto restart
> interrupt, change to use WRRD can reduce interrupt latency. The second is to fix
> multi transfer error in high speed mode. If hardware support auto restart, need driver
> to send master code first.

Please fix checkpatch warning in 2/2, then you get my reviewed-by for
this series:

Reviewed-by:Eddie Huang <eddie.huang@mediatek.com>

> 
> Liguo Zhang (2):
>   i2c: mediatek: add i2c first write then read optimization
>   i2c: mediatek: fix i2c multi transfer issue in high speed mode
> 
>  drivers/i2c/busses/i2c-mt65xx.c | 77 +++++++++++++++++++++++++++++++++++++----
>  1 file changed, 71 insertions(+), 6 deletions(-)