[SRU] [jammy:linux-xilinx-zynqmp 09/14] tty: serial: uartps: Add support for uartps controller reset

[Portia Stephens]

From: Manikanta Guntupalli <manikanta.guntupalli at amd.com>

BugLink: https://bugs.launchpad.net/bugs/2055237

Add support for an optional reset for the uartps controller using
the reset driver. If the uartps node contains the "resets" property,
then cdns_uart_startup performs uartps controller non-pulse out of reset
and reset in exit path.

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli at amd.com>
Link: https://lore.kernel.org/r/20240425062358.1347684-4-manikanta.guntupalli@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit e3896be240780ccade65cc6cc8925c6f12e7f6c6)
Signed-off-by: Portia Stephens <portia.stephens at canonical.com>
---
 drivers/tty/serial/xilinx_uartps.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 8c8689e387aa4..7aa2595b0f9ad 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -25,6 +25,7 @@
 #include <linux/gpio.h>
 #include <linux/gpio/consumer.h>
 #include <linux/delay.h>
+#include <linux/reset.h>
 
 #define CDNS_UART_TTY_NAME	"ttyPS"
 #define CDNS_UART_NAME		"xuartps"
@@ -198,6 +199,7 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
  * @gpiod_rts:		Pointer to the gpio descriptor
  * @rs485_tx_started:	RS485 tx state
  * @tx_timer:		Timer for tx
+ * @rstc:		Pointer to the reset control
  */
 struct cdns_uart {
 	struct uart_port	*port;
@@ -211,6 +213,7 @@ struct cdns_uart {
 	struct gpio_desc	*gpiod_rts;
 	bool			rs485_tx_started;
 	struct hrtimer		tx_timer;
+	struct reset_control	*rstc;
 };
 struct cdns_platform_data {
 	u32 quirks;
@@ -970,6 +973,10 @@ static int cdns_uart_startup(struct uart_port *port)
 
 	is_brk_support = cdns_uart->quirks & CDNS_UART_RXBS_SUPPORT;
 
+	ret = reset_control_deassert(cdns_uart->rstc);
+	if (ret)
+		return ret;
+
 	spin_lock_irqsave(&port->lock, flags);
 
 	/* Disable the TX and RX */
@@ -1796,6 +1803,13 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "clock name 'ref_clk' is deprecated.\n");
 	}
 
+	cdns_uart_data->rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(cdns_uart_data->rstc)) {
+		rc = PTR_ERR(cdns_uart_data->rstc);
+		dev_err_probe(&pdev->dev, rc, "Cannot get UART reset\n");
+		goto err_out_unregister_driver;
+	}
+
 	rc = clk_prepare_enable(cdns_uart_data->pclk);
 	if (rc) {
 		dev_err(&pdev->dev, "Unable to enable pclk clock.\n");
@@ -1967,6 +1981,7 @@ static int cdns_uart_remove(struct platform_device *pdev)
 	if (console_port == port)
 		console_port = NULL;
 #endif
+	reset_control_assert(cdns_uart_data->rstc);
 
 	if (!--instances)
 		uart_unregister_driver(cdns_uart_data->cdns_uart_driver);
-- 
2.34.1