[PATCH v2 3/3] i2c: mt7621: add support for Airoha AN7589

[John Crispin <john@phrozen.org>]

The Airoha AN7589 carries this controller with a second control
register at 0x68. It holds a 16 bit clock divider selected by
SM0CTL2_SCL_DIV_SEL, wider than the 11 bit field in SM0CTL0, and SDA
wait control. The AN7589 also runs without SCL stretching.

Describe the variants as match data: whether to set SCL_STRETCH, and
whether to program the extended divider. The extended divider is set
up before the controller is enabled, and the SM0CTL0 divider stays
zero. With the extended divider and the 200 MHz clock the bus runs
from fast mode plus down to about 3 kHz, where the SM0CTL0 divider
stops at 97.7 kHz.

Signed-off-by: John Crispin <john@phrozen.org>
---
Changes in v2:
- The extended divider supports bus rates down to about 3 kHz with
  the 200 MHz clock. The SM0CTL0 divider stops at 97.7 kHz.
- Set up the extended divider before the controller is enabled. The
  SM0CTL0 divider stays zero.

 drivers/i2c/busses/i2c-mt7621.c | 59 ++++++++++++++++++++++++++++-----
 1 file changed, 51 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mt7621.c b/drivers/i2c/busses/i2c-mt7621.c
index 7a31cc8b89ce..4a6504df0bc1 100644
--- a/drivers/i2c/busses/i2c-mt7621.c
+++ b/drivers/i2c/busses/i2c-mt7621.c
@@ -10,6 +10,7 @@
  * (C) 2014 Sittisak <sittisaks@hotmail.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/i2c.h>
@@ -18,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 #include <linux/reset.h>
 
 #define REG_SM0CFG2_REG		0x28
@@ -28,6 +30,7 @@
 #define REG_PINTEN_REG		0x5c
 #define REG_PINTST_REG		0x60
 #define REG_PINTCL_REG		0x64
+#define REG_SM0CTL2_REG		0x68
 
 /* REG_SM0CFG2_REG */
 #define SM0CFG2_IS_AUTOMODE	BIT(0)
@@ -54,13 +57,25 @@
 #define SM0CTL1_MODE_MASK	(0x7 << 4)
 #define SM0CTL1_TRI		BIT(0)
 
+/* REG_SM0CTL2_REG */
+#define SM0CTL2_DATA_WAIT_SDA	BIT(18)
+#define SM0CTL2_INIT_WAIT_SDA	BIT(17)
+#define SM0CTL2_SCL_DIV_SEL	BIT(16)
+#define SM0CTL2_CLK_DIV_EXT	GENMASK(15, 0)
+
 /* timeout waiting for I2C devices to respond */
 #define TIMEOUT_MS		1000
 
+struct mtk_i2c_soc_data {
+	bool scl_stretch;
+	bool ext_clk_div;
+};
+
 struct mtk_i2c {
 	void __iomem *base;
 	struct device *dev;
 	struct i2c_adapter adap;
+	const struct mtk_i2c_soc_data *soc;
 	u32 bus_freq;
 	u32 clk_div;
 	u32 flags;
@@ -84,6 +99,7 @@ static int mtk_i2c_wait_idle(struct mtk_i2c *i2c)
 
 static void mtk_i2c_reset(struct mtk_i2c *i2c)
 {
+	u32 ctl0;
 	int ret;
 
 	ret = reset_control_assert(i2c->rst);
@@ -96,8 +112,17 @@ static void mtk_i2c_reset(struct mtk_i2c *i2c)
 	 * Don't set SM0CTL0_ODRAIN as its bit meaning is inverted. To
 	 * configure open-drain mode, this bit needs to be cleared.
 	 */
-	iowrite32(((i2c->clk_div << 16) & SM0CTL0_CLK_DIV_MASK) | SM0CTL0_EN |
-		  SM0CTL0_SCL_STRETCH, i2c->base + REG_SM0CTL0_REG);
+	ctl0 = SM0CTL0_EN;
+	if (i2c->soc->ext_clk_div)
+		iowrite32(SM0CTL2_SCL_DIV_SEL | SM0CTL2_DATA_WAIT_SDA |
+			  FIELD_PREP(SM0CTL2_CLK_DIV_EXT, i2c->clk_div),
+			  i2c->base + REG_SM0CTL2_REG);
+	else
+		ctl0 |= (i2c->clk_div << 16) & SM0CTL0_CLK_DIV_MASK;
+	if (i2c->soc->scl_stretch)
+		ctl0 |= SM0CTL0_SCL_STRETCH;
+	iowrite32(ctl0, i2c->base + REG_SM0CTL0_REG);
+
 	iowrite32(0, i2c->base + REG_SM0CFG2_REG);
 }
 
@@ -253,8 +278,17 @@ static const struct i2c_algorithm mtk_i2c_algo = {
 	.functionality = mtk_i2c_func,
 };
 
+static const struct mtk_i2c_soc_data mt7621_i2c_soc_data = {
+	.scl_stretch = true,
+};
+
+static const struct mtk_i2c_soc_data an7589_i2c_soc_data = {
+	.ext_clk_div = true,
+};
+
 static const struct of_device_id i2c_mtk_dt_ids[] = {
-	{ .compatible = "mediatek,mt7621-i2c" },
+	{ .compatible = "mediatek,mt7621-i2c", .data = &mt7621_i2c_soc_data },
+	{ .compatible = "airoha,an7589-i2c", .data = &an7589_i2c_soc_data },
 	{ /* sentinel */ }
 };
 
@@ -262,11 +296,16 @@ MODULE_DEVICE_TABLE(of, i2c_mtk_dt_ids);
 
 static void mtk_i2c_init(struct mtk_i2c *i2c)
 {
-	i2c->clk_div = clk_get_rate(i2c->clk) / i2c->bus_freq - 1;
-	if (i2c->clk_div < 99)
-		i2c->clk_div = 99;
-	if (i2c->clk_div > SM0CTL0_CLK_DIV_MAX)
-		i2c->clk_div = SM0CTL0_CLK_DIV_MAX;
+	unsigned long rate = clk_get_rate(i2c->clk);
+	unsigned long div_min = 99;
+	unsigned long div_max = SM0CTL0_CLK_DIV_MAX;
+
+	if (i2c->soc->ext_clk_div) {
+		div_min = rate / I2C_MAX_FAST_MODE_PLUS_FREQ - 1;
+		div_max = FIELD_MAX(SM0CTL2_CLK_DIV_EXT);
+	}
+
+	i2c->clk_div = clamp(rate / i2c->bus_freq - 1, div_min, div_max);
 
 	mtk_i2c_reset(i2c);
 }
@@ -281,6 +320,10 @@ static int mtk_i2c_probe(struct platform_device *pdev)
 	if (!i2c)
 		return -ENOMEM;
 
+	i2c->soc = device_get_match_data(&pdev->dev);
+	if (!i2c->soc)
+		return -EINVAL;
+
 	i2c->base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
 	if (IS_ERR(i2c->base))
 		return PTR_ERR(i2c->base);
-- 
2.34.1