linux-kernel - [PATCH v3] serial: 8250_bcm7271: Save/restore RTS in suspend/resume

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Message-Id: <20220714031316.404918-1-f.fainelli@gmail.com>
Date:   Wed, 13 Jul 2022 20:13:15 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     linux-serial@...r.kernel.org
Cc:     Doug Berger <opendmb@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Al Cooper <alcooperx@...il.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3] serial: 8250_bcm7271: Save/restore RTS in suspend/resume

From: Doug Berger <opendmb@...il.com>

Commit 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming
from S2") prevented an early enabling of RTS during resume, but it did
not actively restore the RTS state after resume.

Fixes: 9cabe26e65a8 ("serial: 8250_bcm7271: UART errors after resuming from S2")
Signed-off-by: Doug Berger <opendmb@...il.com>
Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
---
Changes in v3:

- moved set_mctrl within the critical section

Changes in v2:

- reworded the commit message to be clearer

 drivers/tty/serial/8250/8250_bcm7271.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index 9b878d023dac..8efdc271eb75 100644
--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -1139,16 +1139,19 @@ static int __maybe_unused brcmuart_suspend(struct device *dev)
 	struct brcmuart_priv *priv = dev_get_drvdata(dev);
 	struct uart_8250_port *up = serial8250_get_port(priv->line);
 	struct uart_port *port = &up->port;
-
-	serial8250_suspend_port(priv->line);
-	clk_disable_unprepare(priv->baud_mux_clk);
+	unsigned long flags;
 
 	/*
 	 * This will prevent resume from enabling RTS before the
-	 *  baud rate has been resored.
+	 *  baud rate has been restored.
 	 */
+	spin_lock_irqsave(&port->lock, flags);
 	priv->saved_mctrl = port->mctrl;
-	port->mctrl = 0;
+	port->mctrl &= ~TIOCM_RTS;
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	serial8250_suspend_port(priv->line);
+	clk_disable_unprepare(priv->baud_mux_clk);
 
 	return 0;
 }
@@ -1158,6 +1161,7 @@ static int __maybe_unused brcmuart_resume(struct device *dev)
 	struct brcmuart_priv *priv = dev_get_drvdata(dev);
 	struct uart_8250_port *up = serial8250_get_port(priv->line);
 	struct uart_port *port = &up->port;
+	unsigned long flags;
 	int ret;
 
 	ret = clk_prepare_enable(priv->baud_mux_clk);
@@ -1180,7 +1184,15 @@ static int __maybe_unused brcmuart_resume(struct device *dev)
 		start_rx_dma(serial8250_get_port(priv->line));
 	}
 	serial8250_resume_port(priv->line);
-	port->mctrl = priv->saved_mctrl;
+
+	if (priv->saved_mctrl & TIOCM_RTS) {
+		/* Restore RTS */
+		spin_lock_irqsave(&port->lock, flags);
+		port->mctrl |= TIOCM_RTS;
+		port->ops->set_mctrl(port, port->mctrl);
+		spin_unlock_irqrestore(&port->lock, flags);
+	}
+
 	return 0;
 }
 
-- 
2.25.1