linux-kernel - [PATCH 3/8] serial: fsl_lpuart: don't restore interrupt state in ISR

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Message-Id: <20210511200148.11934-4-michael@walle.cc>
Date:   Tue, 11 May 2021 22:01:43 +0200
From:   Michael Walle <michael@...le.cc>
To:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Angelo Dureghello <angelo.dureghello@...esys.com>,
        Fugang Duan <fugang.duan@....com>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        Michael Walle <michael@...le.cc>
Subject: [PATCH 3/8] serial: fsl_lpuart: don't restore interrupt state in ISR

Since commit 81e2073c175b ("genirq: Disable interrupts for force
threaded handlers") interrupt handlers that are not explicitly requested
as threaded are always called with interrupts disabled and there is no
need to save the interrupt state when taking the port lock.

This is a preparation for sysrq handling which uses
uart_unlock_and_check_sysrq();

Signed-off-by: Michael Walle <michael@...le.cc>
---
 drivers/tty/serial/fsl_lpuart.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index b76ddc0d8edc..37e02d992c0b 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -824,21 +824,18 @@ static unsigned int lpuart32_tx_empty(struct uart_port *port)
 
 static void lpuart_txint(struct lpuart_port *sport)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&sport->port.lock, flags);
+	spin_lock(&sport->port.lock);
 	lpuart_transmit_buffer(sport);
-	spin_unlock_irqrestore(&sport->port.lock, flags);
+	spin_unlock(&sport->port.lock);
 }
 
 static void lpuart_rxint(struct lpuart_port *sport)
 {
 	unsigned int flg, ignored = 0, overrun = 0;
 	struct tty_port *port = &sport->port.state->port;
-	unsigned long flags;
 	unsigned char rx, sr;
 
-	spin_lock_irqsave(&sport->port.lock, flags);
+	spin_lock(&sport->port.lock);
 
 	while (!(readb(sport->port.membase + UARTSFIFO) & UARTSFIFO_RXEMPT)) {
 		flg = TTY_NORMAL;
@@ -896,28 +893,25 @@ static void lpuart_rxint(struct lpuart_port *sport)
 		writeb(UARTSFIFO_RXOF, sport->port.membase + UARTSFIFO);
 	}
 
-	spin_unlock_irqrestore(&sport->port.lock, flags);
+	spin_unlock(&sport->port.lock);
 
 	tty_flip_buffer_push(port);
 }
 
 static void lpuart32_txint(struct lpuart_port *sport)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&sport->port.lock, flags);
+	spin_lock(&sport->port.lock);
 	lpuart32_transmit_buffer(sport);
-	spin_unlock_irqrestore(&sport->port.lock, flags);
+	spin_unlock(&sport->port.lock);
 }
 
 static void lpuart32_rxint(struct lpuart_port *sport)
 {
 	unsigned int flg, ignored = 0;
 	struct tty_port *port = &sport->port.state->port;
-	unsigned long flags;
 	unsigned long rx, sr;
 
-	spin_lock_irqsave(&sport->port.lock, flags);
+	spin_lock(&sport->port.lock);
 
 	while (!(lpuart32_read(&sport->port, UARTFIFO) & UARTFIFO_RXEMPT)) {
 		flg = TTY_NORMAL;
@@ -965,7 +959,7 @@ static void lpuart32_rxint(struct lpuart_port *sport)
 	}
 
 out:
-	spin_unlock_irqrestore(&sport->port.lock, flags);
+	spin_unlock(&sport->port.lock);
 
 	tty_flip_buffer_push(port);
 }
-- 
2.20.1