openwrt/target/linux/layerscape/patches-5.4/819-uart-0008-MLK-21445-serial-fsl_lpuart-do-HW-reset-for-communic.patch

From d9d113c22c634219cc248a7c6dcf157e2927edad Mon Sep 17 00:00:00 2001
From: Fugang Duan <[email protected]>
Date: Tue, 23 Jul 2019 11:36:22 +0800
Subject: [PATCH] MLK-21445 serial: fsl_lpuart: do HW reset for communication
 port

Do HW reset for communication port after the port is registered
if the UART controller support the feature.

Do partition reset with LPUART's power on, LPUART registers will
keep the previous status, like on i.MX8QM platform,  which is not
expected action, so reset the HW is required.

Currently, only i.MX7ULP and i.MX8QM LPUART controllers include
global register that support HW reset.

Tested-by: Robin Gong <[email protected]>
Tested-by: Peng Fan <[email protected]>
Reviewed-by: Robby Cai <[email protected]>
Signed-off-by: Fugang Duan <[email protected]>
(cherry picked from commit c2bc1f62ec28981462c9cb5ceac17134931ca19f)
Signed-off-by: Arulpandiyan Vadivel <[email protected]>
Signed-off-by: Shrikant Bobade <[email protected]>
(cherry picked from commit 9f396f540093402317c3c1b9a8fe955b91c89164)
---
 drivers/tty/serial/fsl_lpuart.c | 48 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -11,6 +11,7 @@
 
 #include <linux/clk.h>
 #include <linux/console.h>
+#include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/dmapool.h>
@@ -116,6 +117,11 @@
 #define UARTSFIFO_TXOF		0x02
 #define UARTSFIFO_RXUF		0x01
 
+/* 32-bit global registers only for i.MX7ulp/MX8x
+ * The driver only use the reset feature to reset HW.
+ */
+#define UART_GLOBAL		0x8
+
 /* 32-bit register definition */
 #define UARTBAUD		0x00
 #define UARTSTAT		0x04
@@ -230,6 +236,10 @@
 #define UARTWATER_TXWATER_OFF	0
 #define UARTWATER_RXWATER_OFF	16
 
+#define UART_GLOBAL_RST		0x2
+#define RST_HW_MIN_US		20
+#define RST_HW_MAX_US		40
+
 #define UARTFIFO_RXIDEN_RDRF	0x3
 #define UARTCTRL_IDLECFG	0x7
 
@@ -350,6 +360,11 @@ static inline bool is_layerscape_lpuart(
 		sport->devtype == LS1028A_LPUART);
 }
 
+static inline bool is_imx7ulp_lpuart(struct lpuart_port *sport)
+{
+	return sport->devtype == IMX7ULP_LPUART;
+}
+
 static inline bool is_imx8qxp_lpuart(struct lpuart_port *sport)
 {
 	return sport->devtype == IMX8QXP_LPUART;
@@ -413,6 +428,33 @@ static unsigned int lpuart_get_baud_clk_
 #define lpuart_enable_clks(x)	__lpuart_enable_clks(x, true)
 #define lpuart_disable_clks(x)	__lpuart_enable_clks(x, false)
 
+static int lpuart_hw_reset(struct lpuart_port *sport)
+{
+	struct uart_port *port = &sport->port;
+	void __iomem *global_addr;
+	int ret;
+
+	if (uart_console(port))
+		return 0;
+
+	ret = clk_prepare_enable(sport->ipg_clk);
+	if (ret) {
+		dev_err(sport->port.dev, "failed to enable uart ipg clk: %d\n", ret);
+		return ret;
+	}
+
+	if (is_imx7ulp_lpuart(sport) || is_imx8qxp_lpuart(sport)) {
+		global_addr = port->membase + UART_GLOBAL - IMX_REG_OFF;
+		writel(UART_GLOBAL_RST, global_addr);
+		usleep_range(RST_HW_MIN_US, RST_HW_MAX_US);
+		writel(0, global_addr);
+		usleep_range(RST_HW_MIN_US, RST_HW_MAX_US);
+	}
+
+	clk_disable_unprepare(sport->ipg_clk);
+	return 0;
+}
+
 static void lpuart_stop_tx(struct uart_port *port)
 {
 	unsigned char temp;
@@ -2728,6 +2770,10 @@ static int lpuart_probe(struct platform_
 	if (ret)
 		goto failed_attach_port;
 
+	ret = lpuart_hw_reset(sport);
+	if (ret)
+		goto failed_reset;
+
 	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
 
 	if (sport->port.rs485.flags & SER_RS485_RX_DURING_TX)
@@ -2751,6 +2797,8 @@ static int lpuart_probe(struct platform_
 
 	return 0;
 
+failed_reset:
+	uart_remove_one_port(&lpuart_reg, &sport->port);
 failed_attach_port:
 failed_irq_request:
 	lpuart_disable_clks(sport);