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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:14 +0100
Subject: [PATCH 01/18] serial: amba-pl011: 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: Russell King <linux@armlinux.org.uk>
Link: https://lore.kernel.org/r/20240301215246.891055-2-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/amba-pl011.c | 24 ++++++++----------------
1 file changed, 8 insertions(+), 16 deletions(-)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -348,10 +348,7 @@ static int pl011_fifo_to_tty(struct uart
flag = TTY_FRAME;
}
- uart_port_unlock(&uap->port);
- sysrq = uart_handle_sysrq_char(&uap->port, ch & 255);
- uart_port_lock(&uap->port);
-
+ sysrq = uart_prepare_sysrq_char(&uap->port, ch & 255);
if (!sysrq)
uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag);
}
@@ -1017,7 +1014,7 @@ static void pl011_dma_rx_callback(void *
ret = pl011_dma_rx_trigger_dma(uap);
pl011_dma_rx_chars(uap, pending, lastbuf, false);
- uart_port_unlock_irq(&uap->port);
+ uart_unlock_and_check_sysrq(&uap->port);
/*
* Do this check after we picked the DMA chars so we don't
* get some IRQ immediately from RX.
@@ -1540,11 +1537,10 @@ static void check_apply_cts_event_workar
static irqreturn_t pl011_int(int irq, void *dev_id)
{
struct uart_amba_port *uap = dev_id;
- unsigned long flags;
unsigned int status, pass_counter = AMBA_ISR_PASS_LIMIT;
int handled = 0;
- uart_port_lock_irqsave(&uap->port, &flags);
+ uart_port_lock(&uap->port);
status = pl011_read(uap, REG_RIS) & uap->im;
if (status) {
do {
@@ -1573,7 +1569,7 @@ static irqreturn_t pl011_int(int irq, vo
handled = 1;
}
- uart_port_unlock_irqrestore(&uap->port, flags);
+ uart_unlock_and_check_sysrq(&uap->port);
return IRQ_RETVAL(handled);
}
@@ -2322,13 +2318,10 @@ pl011_console_write(struct console *co,
clk_enable(uap->clk);
- local_irq_save(flags);
- if (uap->port.sysrq)
- locked = 0;
- else if (oops_in_progress)
- locked = uart_port_trylock(&uap->port);
+ if (oops_in_progress)
+ locked = uart_port_trylock_irqsave(&uap->port, &flags);
else
- uart_port_lock(&uap->port);
+ uart_port_lock_irqsave(&uap->port, &flags);
/*
* First save the CR then disable the interrupts
@@ -2354,8 +2347,7 @@ pl011_console_write(struct console *co,
pl011_write(old_cr, uap, REG_CR);
if (locked)
- uart_port_unlock(&uap->port);
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(&uap->port, flags);
clk_disable(uap->clk);
}
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