i2c: mediatek: fix I2C usability for MT7981

MT7981 actually uses MediaTek I2C controller v3 instead of v1.
This patch adds support for I2C controller v3 fix fixes the I2C usability
for MT7981.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
diff --git a/drivers/i2c/mtk_i2c.c b/drivers/i2c/mtk_i2c.c
index 5528bcd..2f331d3 100644
--- a/drivers/i2c/mtk_i2c.c
+++ b/drivers/i2c/mtk_i2c.c
@@ -183,9 +183,36 @@
 	[REG_DCM_EN] = 0xf88,
 };
 
+static const uint mt_i2c_regs_v3[] = {
+	[REG_PORT] = 0x0,
+	[REG_INTR_MASK] = 0x8,
+	[REG_INTR_STAT] = 0xc,
+	[REG_CONTROL] = 0x10,
+	[REG_TRANSFER_LEN] = 0x14,
+	[REG_TRANSAC_LEN] = 0x18,
+	[REG_DELAY_LEN] = 0x1c,
+	[REG_TIMING] = 0x20,
+	[REG_START] = 0x24,
+	[REG_EXT_CONF] = 0x28,
+	[REG_LTIMING] = 0x2c,
+	[REG_HS] = 0x30,
+	[REG_IO_CONFIG] = 0x34,
+	[REG_FIFO_ADDR_CLR] = 0x38,
+	[REG_TRANSFER_LEN_AUX] = 0x44,
+	[REG_CLOCK_DIV] = 0x48,
+	[REG_SOFTRESET] = 0x50,
+	[REG_SLAVE_ADDR] = 0x94,
+	[REG_DEBUGSTAT] = 0xe4,
+	[REG_DEBUGCTRL] = 0xe8,
+	[REG_FIFO_STAT] = 0xf4,
+	[REG_FIFO_THRESH] = 0xf8,
+	[REG_DCM_EN] = 0xf88,
+};
+
 struct mtk_i2c_soc_data {
 	const uint *regs;
 	uint dma_sync: 1;
+	uint ltiming_adjust: 1;
 };
 
 struct mtk_i2c_priv {
@@ -401,6 +428,10 @@
 				(sample_cnt << HS_SAMPLE_OFFSET) |
 				(step_cnt << HS_STEP_OFFSET);
 		i2c_writel(priv, REG_HS, high_speed_reg);
+		if (priv->soc_data->ltiming_adjust) {
+			timing_reg = (sample_cnt << 12) | (step_cnt << 9);
+			i2c_writel(priv, REG_LTIMING, timing_reg);
+		}
 	} else {
 		ret = mtk_i2c_calculate_speed(clk_src, priv->speed,
 					      &step_cnt, &sample_cnt);
@@ -412,7 +443,12 @@
 		high_speed_reg = I2C_TIME_CLR_VALUE;
 		i2c_writel(priv, REG_TIMING, timing_reg);
 		i2c_writel(priv, REG_HS, high_speed_reg);
+		if (priv->soc_data->ltiming_adjust) {
+			timing_reg = (sample_cnt << 6) | step_cnt;
+			i2c_writel(priv, REG_LTIMING, timing_reg);
+		}
 	}
+
 exit:
 	if (mtk_i2c_clk_disable(priv))
 		return log_msg_ret("set_speed disable clk", -1);
@@ -725,7 +761,6 @@
 		return log_msg_ret("probe enable clk", -1);
 
 	mtk_i2c_init_hw(priv);
-
 	if (mtk_i2c_clk_disable(priv))
 		return log_msg_ret("probe disable clk", -1);
 
@@ -750,31 +785,37 @@
 static const struct mtk_i2c_soc_data mt76xx_soc_data = {
 	.regs = mt_i2c_regs_v1,
 	.dma_sync = 0,
+	.ltiming_adjust = 0,
 };
 
 static const struct mtk_i2c_soc_data mt7981_soc_data = {
-	.regs = mt_i2c_regs_v1,
+	.regs = mt_i2c_regs_v3,
 	.dma_sync = 1,
+	.ltiming_adjust = 1,
 };
 
 static const struct mtk_i2c_soc_data mt7986_soc_data = {
 	.regs = mt_i2c_regs_v1,
 	.dma_sync = 1,
+	.ltiming_adjust = 0,
 };
 
 static const struct mtk_i2c_soc_data mt8183_soc_data = {
 	.regs = mt_i2c_regs_v2,
 	.dma_sync = 1,
+	.ltiming_adjust = 0,
 };
 
 static const struct mtk_i2c_soc_data mt8518_soc_data = {
 	.regs = mt_i2c_regs_v1,
 	.dma_sync = 0,
+	.ltiming_adjust = 0,
 };
 
 static const struct mtk_i2c_soc_data mt8512_soc_data = {
 	.regs = mt_i2c_regs_v1,
 	.dma_sync = 1,
+	.ltiming_adjust = 0,
 };
 
 static const struct dm_i2c_ops mtk_i2c_ops = {