linux-kernel - [PATCH V3 3/3] tty: serial: uartps: Add support for uartps controller reset

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Message-ID: <20240425062358.1347684-4-manikanta.guntupalli@amd.com>
Date: Thu, 25 Apr 2024 11:53:58 +0530
From: Manikanta Guntupalli <manikanta.guntupalli@....com>
To: <git@....com>, <gregkh@...uxfoundation.org>, <jirislaby@...nel.org>,
	<robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
	<michal.simek@....com>, <p.zabel@...gutronix.de>,
	<laurent.pinchart@...asonboard.com>, <radhey.shyam.pandey@....com>,
	<parth.gajjar@....com>, <u.kleine-koenig@...gutronix.de>,
	<tglx@...utronix.de>, <julien.malik@...eenlabs.fr>, <ruanjinjie@...wei.com>,
	<linux-kernel@...r.kernel.org>, <linux-serial@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
CC: <srinivas.goud@....com>, <shubhrajyoti.datta@....com>,
	<manion05gk@...il.com>, Manikanta Guntupalli <manikanta.guntupalli@....com>
Subject: [PATCH V3 3/3] tty: serial: uartps: Add support for uartps controller reset

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@....com>
---
Changes for V2:
Remove check for reset_control_deassert, as reset_control_deassert
function internally has NULL check.
Changes for V3:
None.
---
 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 de3487206bcb..2acfcea403ce 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;
@@ -948,6 +951,10 @@ 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;
+
 	uart_port_lock_irqsave(port, &flags);
 
 	/* Disable the TX and RX */
@@ -1721,6 +1728,13 @@ 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");
@@ -1881,6 +1895,7 @@ static void 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);
-- 
2.25.1