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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:23 +0100
Subject: [PATCH 10/18] serial: owl: Use uart_prepare_sysrq_char() to handle
sysrq.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz
The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT.
The driver splits the locking function into two parts: local_irq_save() and
uart_port_lock() and this breaks PREEMPT_RT.
Handle sysrq requests sysrq once the port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.
Cc: Andreas Färber <afaerber@suse.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-actions@lists.infradead.org
Link: https://lore.kernel.org/r/20240301215246.891055-11-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/owl-uart.c | 30 ++++++++++++------------------
1 file changed, 12 insertions(+), 18 deletions(-)
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -199,6 +199,7 @@ static void owl_uart_receive_chars(struc
stat = owl_uart_read(port, OWL_UART_STAT);
while (!(stat & OWL_UART_STAT_RFEM)) {
char flag = TTY_NORMAL;
+ bool sysrq;
if (stat & OWL_UART_STAT_RXER)
port->icount.overrun++;
@@ -217,7 +218,9 @@ static void owl_uart_receive_chars(struc
val = owl_uart_read(port, OWL_UART_RXDAT);
val &= 0xff;
- if ((stat & port->ignore_status_mask) == 0)
+ sysrq = uart_prepare_sysrq_char(port, val);
+
+ if (!sysrq && (stat & port->ignore_status_mask) == 0)
tty_insert_flip_char(&port->state->port, val, flag);
stat = owl_uart_read(port, OWL_UART_STAT);
@@ -229,10 +232,9 @@ static void owl_uart_receive_chars(struc
static irqreturn_t owl_uart_irq(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
- unsigned long flags;
u32 stat;
- uart_port_lock_irqsave(port, &flags);
+ uart_port_lock(port);
stat = owl_uart_read(port, OWL_UART_STAT);
@@ -246,7 +248,7 @@ static irqreturn_t owl_uart_irq(int irq,
stat |= OWL_UART_STAT_RIP | OWL_UART_STAT_TIP;
owl_uart_write(port, stat, OWL_UART_STAT);
- uart_port_unlock_irqrestore(port, flags);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
@@ -508,18 +510,12 @@ static void owl_uart_port_write(struct u
{
u32 old_ctl, val;
unsigned long flags;
- int locked;
+ int locked = 1;
- local_irq_save(flags);
-
- if (port->sysrq)
- locked = 0;
- else if (oops_in_progress)
- locked = uart_port_trylock(port);
- else {
- uart_port_lock(port);
- locked = 1;
- }
+ if (oops_in_progress)
+ locked = uart_port_trylock_irqsave(port, &flags);
+ else
+ uart_port_lock_irqsave(port, &flags);
old_ctl = owl_uart_read(port, OWL_UART_CTL);
val = old_ctl | OWL_UART_CTL_TRFS_TX;
@@ -541,9 +537,7 @@ static void owl_uart_port_write(struct u
owl_uart_write(port, old_ctl, OWL_UART_CTL);
if (locked)
- uart_port_unlock(port);
-
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static void owl_uart_console_write(struct console *co, const char *s,
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