[PATCH v2 07/14] serial: mediatek: add special handling for highspeed and linux compat

[Christian Marangi]

Upstream linux serial driver use a different logic to setup serial regs.

They have 2 interval:
- < 115200 we use lowspeed regs and 16 * baud
- >= 115200 we use highspeed

We currently use force_highspeed property to force usage of highspeed
regs even with low baud rate.

Add special handling if the upstream compatible is used where we just
apply the same interval with anything >= 115200 in highspeed simulating
force_highspeed.

Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
---
 drivers/serial/serial_mtk.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/serial/serial_mtk.c b/drivers/serial/serial_mtk.c
index d34a31c9cf0..14be095653a 100644
--- a/drivers/serial/serial_mtk.c
+++ b/drivers/serial/serial_mtk.c
@@ -89,8 +89,8 @@ struct mtk_serial_priv {
 	bool force_highspeed;
 };
 
-static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud,
-			       uint clk_rate)
+static void _mtk_serial_setbrg(struct udevice *dev, struct mtk_serial_priv *priv,
+			       int baud, uint clk_rate)
 {
 	u32 quot, realbaud, samplecount = 1;
 
@@ -113,7 +113,12 @@ static void _mtk_serial_setbrg(struct mtk_serial_priv *priv, int baud,
 		goto set_baud;
 	}
 
-	if (priv->force_highspeed)
+	/*
+	 * Upstream linux use highspeed for anything >= 115200 and lowspeed
+	 * for < 115200. Simulate this if we are using the upstream compatible.
+	 */
+	if (priv->force_highspeed ||
+	    (device_is_compatible(dev, "mediatek,mt6577-uart") && baud >= 115200))
 		goto use_hs3;
 
 	if (baud <= 115200) {
@@ -186,7 +191,7 @@ static int mtk_serial_setbrg(struct udevice *dev, int baudrate)
 	if (IS_ERR_VALUE(clk_rate) || clk_rate == 0)
 		clk_rate = priv->fixed_clk_rate;
 
-	_mtk_serial_setbrg(priv, baudrate, clk_rate);
+	_mtk_serial_setbrg(dev, priv, baudrate, clk_rate);
 
 	return 0;
 }
@@ -302,13 +307,13 @@ DECLARE_GLOBAL_DATA_PTR;
 		writel(0, &mtk_hsuart##port.regs->ier); \
 		writel(UART_MCRVAL, &mtk_hsuart##port.regs->mcr); \
 		writel(UART_FCRVAL, &mtk_hsuart##port.regs->fcr); \
-		_mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
+		_mtk_serial_setbrg(NULL, &mtk_hsuart##port, gd->baudrate, \
 				   mtk_hsuart##port.fixed_clk_rate); \
 		return 0 ; \
 	} \
 	static void mtk_serial##port##_setbrg(void) \
 	{ \
-		_mtk_serial_setbrg(&mtk_hsuart##port, gd->baudrate, \
+		_mtk_serial_setbrg(NULL, &mtk_hsuart##port, gd->baudrate, \
 				   mtk_hsuart##port.fixed_clk_rate); \
 	} \
 	static int mtk_serial##port##_getc(void) \
@@ -456,7 +461,7 @@ static inline void _debug_uart_init(void)
 	writel(UART_MCRVAL, &priv.regs->mcr);
 	writel(UART_FCRVAL, &priv.regs->fcr);
 
-	_mtk_serial_setbrg(&priv, CONFIG_BAUDRATE, priv.fixed_clk_rate);
+	_mtk_serial_setbrg(NULL, &priv, CONFIG_BAUDRATE, priv.fixed_clk_rate);
 }
 
 static inline void _debug_uart_putc(int ch)
-- 
2.43.0