[tty,v1,41/74] serial: msm: Use port lock wrappers

Commit Message

John Ogness Sept. 14, 2023, 6:37 p.m. UTC

From: Thomas Gleixner <[e-mail]>

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 <[e-mail]>
---
 drivers/tty/serial/msm_serial.c | 38 ++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 19 deletions(-)

Comments

Bjorn Andersson Sept. 14, 2023, 7:13 p.m. UTC | #1

On Thu, Sep 14, 2023 at 08:43:58PM +0206, John Ogness wrote:
> From: Thomas Gleixner <[e-mail]>
> 
> 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 <[e-mail]>

Reviewed-by: Bjorn Andersson <[e-mail]>

Regards,
Bjorn

Patch

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 90953e679e38..597264b546fd 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -444,7 +444,7 @@  static void msm_complete_tx_dma(void *args)
 	unsigned int count;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	/* Already stopped */
 	if (!dma->count)
@@ -476,7 +476,7 @@  static void msm_complete_tx_dma(void *args)
 
 	msm_handle_tx(port);
 done:
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 }
 
 static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
@@ -549,7 +549,7 @@  static void msm_complete_rx_dma(void *args)
 	unsigned long flags;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	/* Already stopped */
 	if (!dma->count)
@@ -587,16 +587,16 @@  static void msm_complete_rx_dma(void *args)
 		if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
 			flag = TTY_NORMAL;
 
-		spin_unlock_irqrestore(&port->lock, flags);
+		uart_port_unlock_irqrestore(port, flags);
 		sysrq = uart_handle_sysrq_char(port, dma->virt[i]);
-		spin_lock_irqsave(&port->lock, flags);
+		uart_port_lock_irqsave(port, &flags);
 		if (!sysrq)
 			tty_insert_flip_char(tport, dma->virt[i], flag);
 	}
 
 	msm_start_rx_dma(msm_port);
 done:
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	if (count)
 		tty_flip_buffer_push(tport);
@@ -762,9 +762,9 @@  static void msm_handle_rx_dm(struct uart_port *port, unsigned int misr)
 			if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
 				flag = TTY_NORMAL;
 
-			spin_unlock(&port->lock);
+			uart_port_unlock(port);
 			sysrq = uart_handle_sysrq_char(port, buf[i]);
-			spin_lock(&port->lock);
+			uart_port_lock(port);
 			if (!sysrq)
 				tty_insert_flip_char(tport, buf[i], flag);
 		}
@@ -824,9 +824,9 @@  static void msm_handle_rx(struct uart_port *port)
 		else if (sr & MSM_UART_SR_PAR_FRAME_ERR)
 			flag = TTY_FRAME;
 
-		spin_unlock(&port->lock);
+		uart_port_unlock(port);
 		sysrq = uart_handle_sysrq_char(port, c);
-		spin_lock(&port->lock);
+		uart_port_lock(port);
 		if (!sysrq)
 			tty_insert_flip_char(tport, c, flag);
 	}
@@ -951,7 +951,7 @@  static irqreturn_t msm_uart_irq(int irq, void *dev_id)
 	unsigned int misr;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	misr = msm_read(port, MSM_UART_MISR);
 	msm_write(port, 0, MSM_UART_IMR); /* disable interrupt */
 
@@ -983,7 +983,7 @@  static irqreturn_t msm_uart_irq(int irq, void *dev_id)
 		msm_handle_delta_cts(port);
 
 	msm_write(port, msm_port->imr, MSM_UART_IMR); /* restore interrupt */
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	return IRQ_HANDLED;
 }
@@ -1128,13 +1128,13 @@  static int msm_set_baud_rate(struct uart_port *port, unsigned int baud,
 	unsigned long flags, rate;
 
 	flags = *saved_flags;
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	entry = msm_find_best_baud(port, baud, &rate);
 	clk_set_rate(msm_port->clk, rate);
 	baud = rate / 16 / entry->divisor;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	*saved_flags = flags;
 	port->uartclk = rate;
 
@@ -1266,7 +1266,7 @@  static void msm_set_termios(struct uart_port *port, struct ktermios *termios,
 	unsigned long flags;
 	unsigned int baud, mr;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	if (dma->chan) /* Terminate if any */
 		msm_stop_dma(port, dma);
@@ -1338,7 +1338,7 @@  static void msm_set_termios(struct uart_port *port, struct ktermios *termios,
 	/* Try to use DMA */
 	msm_start_rx_dma(msm_port);
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 }
 
 static const char *msm_type(struct uart_port *port)
@@ -1620,9 +1620,9 @@  static void __msm_console_write(struct uart_port *port, const char *s,
 	if (port->sysrq)
 		locked = 0;
 	else if (oops_in_progress)
-		locked = spin_trylock(&port->lock);
+		locked = uart_port_trylock(port);
 	else
-		spin_lock(&port->lock);
+		uart_port_lock(port);
 
 	if (is_uartdm)
 		msm_reset_dm_count(port, count);
@@ -1661,7 +1661,7 @@  static void __msm_console_write(struct uart_port *port, const char *s,
 	}
 
 	if (locked)
-		spin_unlock(&port->lock);
+		uart_port_unlock(port);
 
 	local_irq_restore(flags);
 }