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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:17 +0100
Subject: [PATCH 04/18] serial: meson: Use uart_prepare_sysrq_char().
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.
Delay handling sysrq until port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-amlogic@lists.infradead.org
Link: https://lore.kernel.org/r/20240301215246.891055-5-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/meson_uart.c | 22 ++++++++--------------
1 file changed, 8 insertions(+), 14 deletions(-)
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -220,7 +220,7 @@ static void meson_receive_chars(struct u
continue;
}
- if (uart_handle_sysrq_char(port, ch))
+ if (uart_prepare_sysrq_char(port, ch))
continue;
if ((status & port->ignore_status_mask) == 0)
@@ -248,7 +248,7 @@ static irqreturn_t meson_uart_interrupt(
meson_uart_start_tx(port);
}
- uart_port_unlock(port);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
@@ -556,18 +556,13 @@ static void meson_serial_port_write(stru
u_int count)
{
unsigned long flags;
- int locked;
+ int locked = 1;
u32 val, tmp;
- 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);
val = readl(port->membase + AML_UART_CONTROL);
tmp = val & ~(AML_UART_TX_INT_EN | AML_UART_RX_INT_EN);
@@ -577,8 +572,7 @@ static void meson_serial_port_write(stru
writel(val, port->membase + AML_UART_CONTROL);
if (locked)
- uart_port_unlock(port);
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static void meson_serial_console_write(struct console *co, const char *s,
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