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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 1 Mar 2024 22:45:18 +0100
Subject: [PATCH 05/18] serial: msm: 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: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Link: https://lore.kernel.org/r/20240301215246.891055-6-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/tty/serial/msm_serial.c | 33 ++++++++++-----------------------
1 file changed, 10 insertions(+), 23 deletions(-)
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -588,16 +588,14 @@ static void msm_complete_rx_dma(void *ar
if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
flag = TTY_NORMAL;
- uart_port_unlock_irqrestore(port, flags);
- sysrq = uart_handle_sysrq_char(port, dma->virt[i]);
- uart_port_lock_irqsave(port, &flags);
+ sysrq = uart_prepare_sysrq_char(port, dma->virt[i]);
if (!sysrq)
tty_insert_flip_char(tport, dma->virt[i], flag);
}
msm_start_rx_dma(msm_port);
done:
- uart_port_unlock_irqrestore(port, flags);
+ uart_unlock_and_check_sysrq_irqrestore(port, flags);
if (count)
tty_flip_buffer_push(tport);
@@ -763,9 +761,7 @@ static void msm_handle_rx_dm(struct uart
if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
flag = TTY_NORMAL;
- uart_port_unlock(port);
- sysrq = uart_handle_sysrq_char(port, buf[i]);
- uart_port_lock(port);
+ sysrq = uart_prepare_sysrq_char(port, buf[i]);
if (!sysrq)
tty_insert_flip_char(tport, buf[i], flag);
}
@@ -825,9 +821,7 @@ static void msm_handle_rx(struct uart_po
else if (sr & MSM_UART_SR_PAR_FRAME_ERR)
flag = TTY_FRAME;
- uart_port_unlock(port);
- sysrq = uart_handle_sysrq_char(port, c);
- uart_port_lock(port);
+ sysrq = uart_prepare_sysrq_char(port, c);
if (!sysrq)
tty_insert_flip_char(tport, c, flag);
}
@@ -948,11 +942,10 @@ static irqreturn_t msm_uart_irq(int irq,
struct uart_port *port = dev_id;
struct msm_port *msm_port = to_msm_port(port);
struct msm_dma *dma = &msm_port->rx_dma;
- unsigned long flags;
unsigned int misr;
u32 val;
- uart_port_lock_irqsave(port, &flags);
+ uart_port_lock(port);
misr = msm_read(port, MSM_UART_MISR);
msm_write(port, 0, MSM_UART_IMR); /* disable interrupt */
@@ -984,7 +977,7 @@ static irqreturn_t msm_uart_irq(int irq,
msm_handle_delta_cts(port);
msm_write(port, msm_port->imr, MSM_UART_IMR); /* restore interrupt */
- uart_port_unlock_irqrestore(port, flags);
+ uart_unlock_and_check_sysrq(port);
return IRQ_HANDLED;
}
@@ -1621,14 +1614,10 @@ static void __msm_console_write(struct u
num_newlines++;
count += num_newlines;
- local_irq_save(flags);
-
- if (port->sysrq)
- locked = 0;
- else if (oops_in_progress)
- locked = uart_port_trylock(port);
+ if (oops_in_progress)
+ locked = uart_port_trylock_irqsave(port, &flags);
else
- uart_port_lock(port);
+ uart_port_lock_irqsave(port, &flags);
if (is_uartdm)
msm_reset_dm_count(port, count);
@@ -1667,9 +1656,7 @@ static void __msm_console_write(struct u
}
if (locked)
- uart_port_unlock(port);
-
- local_irq_restore(flags);
+ uart_port_unlock_irqrestore(port, flags);
}
static void msm_console_write(struct console *co, const char *s,
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