linux-kernel - [PATCH 1/1] i2c: designware: Add SMBus Quick Command support

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Message-Id: <20250412021822.372805-1-ende.tan@starfivetech.com>
Date: Sat, 12 Apr 2025 10:18:22 +0800
From: ende.tan@...rfivetech.com
To: linux-i2c@...r.kernel.org
Cc: jarkko.nikula@...ux.intel.com,
	andriy.shevchenko@...ux.intel.com,
	mika.westerberg@...ux.intel.com,
	jsd@...ihalf.com,
	andi.shyti@...nel.org,
	linux-kernel@...r.kernel.org,
	leyfoon.tan@...rfivetech.com,
	endeneer@...il.com,
	Tan En De <ende.tan@...rfivetech.com>
Subject: [PATCH 1/1] i2c: designware: Add SMBus Quick Command support

From: Tan En De <ende.tan@...rfivetech.com>

Add support for SMBus Quick Read and Quick Write commands.

Signed-off-by: Tan En De <ende.tan@...rfivetech.com>
---
 drivers/i2c/busses/i2c-designware-core.h   |  4 ++++
 drivers/i2c/busses/i2c-designware-master.c | 18 +++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 347843b4f5dd..91f17181ece1 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -40,6 +40,8 @@
 
 #define DW_IC_DATA_CMD_DAT			GENMASK(7, 0)
 #define DW_IC_DATA_CMD_FIRST_DATA_BYTE		BIT(11)
+#define DW_IC_DATA_CMD_STOP			BIT(9)
+#define DW_IC_DATA_CMD_CMD			BIT(8)
 
 /*
  * Registers offset
@@ -123,7 +125,9 @@
 
 #define DW_IC_ERR_TX_ABRT			0x1
 
+#define DW_IC_TAR_SMBUS_QUICK_CMD		BIT(16)
 #define DW_IC_TAR_10BITADDR_MASTER		BIT(12)
+#define DW_IC_TAR_SPECIAL			BIT(11)
 
 #define DW_IC_COMP_PARAM_1_SPEED_MODE_HIGH	(BIT(2) | BIT(3))
 #define DW_IC_COMP_PARAM_1_SPEED_MODE_MASK	GENMASK(3, 2)
diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index c5394229b77f..bd5812f1168e 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -268,6 +268,10 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
 	regmap_update_bits(dev->map, DW_IC_CON, DW_IC_CON_10BITADDR_MASTER,
 			   ic_con);
 
+	/* i2c-core-smbus.c: Only I2C_SMBUS_QUICK has msg[0].len = 0 */
+	if (dev->msgs[0].len == 0)
+		ic_tar |= DW_IC_TAR_SMBUS_QUICK_CMD | DW_IC_TAR_SPECIAL;
+
 	/*
 	 * Set the slave (target) address and enable 10-bit addressing mode
 	 * if applicable.
@@ -474,6 +478,16 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 		regmap_read(dev->map, DW_IC_RXFLR, &flr);
 		rx_limit = dev->rx_fifo_depth - flr;
 
+		/* i2c-core-smbus.c: Only I2C_SMBUS_QUICK has msg[0].len = 0 */
+		if (buf_len == 0 && tx_limit > 0 && rx_limit > 0) {
+			regmap_write(
+				dev->map, DW_IC_DATA_CMD,
+				*buf | DW_IC_DATA_CMD_STOP |
+				((msgs[dev->msg_write_idx].flags & I2C_M_RD) ?
+				DW_IC_DATA_CMD_CMD : 0)
+			);
+		}
+
 		while (buf_len > 0 && tx_limit > 0 && rx_limit > 0) {
 			u32 cmd = 0;
 
@@ -919,7 +933,9 @@ void i2c_dw_configure_master(struct dw_i2c_dev *dev)
 {
 	struct i2c_timings *t = &dev->timings;
 
-	dev->functionality = I2C_FUNC_10BIT_ADDR | DW_IC_DEFAULT_FUNCTIONALITY;
+	dev->functionality = I2C_FUNC_10BIT_ADDR |
+			     I2C_FUNC_SMBUS_QUICK |
+			     DW_IC_DEFAULT_FUNCTIONALITY;
 
 	dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
 			  DW_IC_CON_RESTART_EN;
-- 
2.34.1