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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:24 +0100
Subject: [PATCH 11/18] serial: rda: Use uart_prepare_sysrq_char() to handle
sysrq.
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: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-unisoc@lists.infradead.org
Link: https://lore.kernel.org/r/20240301215246.891055-12-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/rda-uart.c | 28 ++++++++++------------------
1 file changed, 10 insertions(+), 18 deletions(-)
--- a/drivers/tty/serial/rda-uart.c
+++ b/drivers/tty/serial/rda-uart.c
@@ -394,7 +394,8 @@ static void rda_uart_receive_chars(struc
val &= 0xff;
port->icount.rx++;
- tty_insert_flip_char(&port->state->port, val, flag);
+ if (!uart_prepare_sysrq_char(port, val))
+ tty_insert_flip_char(&port->state->port, val, flag);
status = rda_uart_read(port, RDA_UART_STATUS);
}
@@ -405,10 +406,9 @@ static void rda_uart_receive_chars(struc
static irqreturn_t rda_interrupt(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
- unsigned long flags;
u32 val, irq_mask;
- uart_port_lock_irqsave(port, &flags);
+ uart_port_lock(port);
/* Clear IRQ cause */
val = rda_uart_read(port, RDA_UART_IRQ_CAUSE);
@@ -425,7 +425,7 @@ static irqreturn_t rda_interrupt(int irq
rda_uart_send_chars(port);
}
- uart_port_unlock_irqrestore(port, flags);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
@@ -590,18 +590,12 @@ static void rda_uart_port_write(struct u
{
u32 old_irq_mask;
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_irq_mask = rda_uart_read(port, RDA_UART_IRQ_MASK);
rda_uart_write(port, 0, RDA_UART_IRQ_MASK);
@@ -615,9 +609,7 @@ static void rda_uart_port_write(struct u
rda_uart_write(port, old_irq_mask, RDA_UART_IRQ_MASK);
if (locked)
- uart_port_unlock(port);
-
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static void rda_uart_console_write(struct console *co, const char *s,
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