From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 14 Sep 2023 20:43:22 +0206
Subject: [PATCH 005/134] serial: 8250_bcm7271: Use port lock wrappers
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz

When a serial port is used for kernel console output, then all
modifications to the UART registers which are done from other contexts,
e.g. getty, termios, are interference points for the kernel console.

So far this has been ignored and the printk output is based on the
principle of hope. The rework of the console infrastructure which aims to
support threaded and atomic consoles, requires to mark sections which
modify the UART registers as unsafe. This allows the atomic write function
to make informed decisions and eventually to restore operational state. It
also allows to prevent the regular UART code from modifying UART registers
while printk output is in progress.

All modifications of UART registers are guarded by the UART port lock,
which provides an obvious synchronization point with the console
infrastructure.

To avoid adding this functionality to all UART drivers, wrap the
spin_[un]lock*() invocations for uart_port::lock into helper functions
which just contain the spin_[un]lock*() invocations for now. In a
subsequent step these helpers will gain the console synchronization
mechanisms.

Converted with coccinelle. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20230914183831.587273-6-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/tty/serial/8250/8250_bcm7271.c |   28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -567,7 +567,7 @@ static irqreturn_t brcmuart_isr(int irq,
 	if (interrupts == 0)
 		return IRQ_NONE;
 
-	spin_lock_irqsave(&up->lock, flags);
+	uart_port_lock_irqsave(up, &flags);
 
 	/* Clear all interrupts */
 	udma_writel(priv, REGS_DMA_ISR, UDMA_INTR_CLEAR, interrupts);
@@ -581,7 +581,7 @@ static irqreturn_t brcmuart_isr(int irq,
 	if ((rval | tval) == 0)
 		dev_warn(dev, "Spurious interrupt: 0x%x\n", interrupts);
 
-	spin_unlock_irqrestore(&up->lock, flags);
+	uart_port_unlock_irqrestore(up, flags);
 	return IRQ_HANDLED;
 }
 
@@ -608,10 +608,10 @@ static int brcmuart_startup(struct uart_
 	 *
 	 * Synchronize UART_IER access against the console.
 	 */
-	spin_lock_irq(&port->lock);
+	uart_port_lock_irq(port);
 	up->ier &= ~UART_IER_RDI;
 	serial_port_out(port, UART_IER, up->ier);
-	spin_unlock_irq(&port->lock);
+	uart_port_unlock_irq(port);
 
 	priv->tx_running = false;
 	priv->dma.rx_dma = NULL;
@@ -629,7 +629,7 @@ static void brcmuart_shutdown(struct uar
 	struct brcmuart_priv *priv = up->port.private_data;
 	unsigned long flags;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	priv->shutdown = true;
 	if (priv->dma_enabled) {
 		stop_rx_dma(up);
@@ -645,7 +645,7 @@ static void brcmuart_shutdown(struct uar
 	 */
 	up->dma = NULL;
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 	serial8250_do_shutdown(port);
 }
 
@@ -788,7 +788,7 @@ static int brcmuart_handle_irq(struct ua
 	 * interrupt but there is no data ready.
 	 */
 	if (((iir & UART_IIR_ID) == UART_IIR_RX_TIMEOUT) && !(priv->shutdown)) {
-		spin_lock_irqsave(&p->lock, flags);
+		uart_port_lock_irqsave(p, &flags);
 		status = serial_port_in(p, UART_LSR);
 		if ((status & UART_LSR_DR) == 0) {
 
@@ -813,7 +813,7 @@ static int brcmuart_handle_irq(struct ua
 
 			handled = 1;
 		}
-		spin_unlock_irqrestore(&p->lock, flags);
+		uart_port_unlock_irqrestore(p, flags);
 		if (handled)
 			return 1;
 	}
@@ -831,7 +831,7 @@ static enum hrtimer_restart brcmuart_hrt
 	if (priv->shutdown)
 		return HRTIMER_NORESTART;
 
-	spin_lock_irqsave(&p->lock, flags);
+	uart_port_lock_irqsave(p, &flags);
 	status = serial_port_in(p, UART_LSR);
 
 	/*
@@ -855,7 +855,7 @@ static enum hrtimer_restart brcmuart_hrt
 		status |= UART_MCR_RTS;
 		serial_port_out(p, UART_MCR, status);
 	}
-	spin_unlock_irqrestore(&p->lock, flags);
+	uart_port_unlock_irqrestore(p, flags);
 	return HRTIMER_NORESTART;
 }
 
@@ -1154,10 +1154,10 @@ static int __maybe_unused brcmuart_suspe
 	 * This will prevent resume from enabling RTS before the
 	 *  baud rate has been restored.
 	 */
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	priv->saved_mctrl = port->mctrl;
 	port->mctrl &= ~TIOCM_RTS;
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	serial8250_suspend_port(priv->line);
 	clk_disable_unprepare(priv->baud_mux_clk);
@@ -1196,10 +1196,10 @@ static int __maybe_unused brcmuart_resum
 
 	if (priv->saved_mctrl & TIOCM_RTS) {
 		/* Restore RTS */
-		spin_lock_irqsave(&port->lock, flags);
+		uart_port_lock_irqsave(port, &flags);
 		port->mctrl |= TIOCM_RTS;
 		port->ops->set_mctrl(port, port->mctrl);
-		spin_unlock_irqrestore(&port->lock, flags);
+		uart_port_unlock_irqrestore(port, flags);
 	}
 
 	return 0;
