serial: bfin_5xx: split uart RX lock from uart port lock to avoid deadlock
The RX lock is used to protect the RX buffer from concurrent access in DMA
mode between the timer and RX interrupt routines. It is independent from
the uart lock which is used to protect the TX buffer. It is possible for
a uart TX transfer to be started up from the RX interrupt handler if low
latency is enabled. So we need to split the locks to avoid deadlocking in
this situation.
In PIO mode, the RX lock is not necessary because the handle_simple_irq
and handle_level_irq functions ensure driver interrupt handlers are called
once on one core.
And now that the RX path has its own lock, the TX interrupt has nothing to
do with the RX path, so disabling it at the same time.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/tty/serial/bfin_5xx.c b/drivers/tty/serial/bfin_5xx.c
index e381b89..9b1ff2b 100644
--- a/drivers/tty/serial/bfin_5xx.c
+++ b/drivers/tty/serial/bfin_5xx.c
@@ -370,10 +370,8 @@
{
struct bfin_serial_port *uart = dev_id;
- spin_lock(&uart->port.lock);
while (UART_GET_LSR(uart) & DR)
bfin_serial_rx_chars(uart);
- spin_unlock(&uart->port.lock);
return IRQ_HANDLED;
}
@@ -490,9 +488,8 @@
{
int x_pos, pos;
- dma_disable_irq(uart->tx_dma_channel);
- dma_disable_irq(uart->rx_dma_channel);
- spin_lock_bh(&uart->port.lock);
+ dma_disable_irq_nosync(uart->rx_dma_channel);
+ spin_lock_bh(&uart->rx_lock);
/* 2D DMA RX buffer ring is used. Because curr_y_count and
* curr_x_count can't be read as an atomic operation,
@@ -523,8 +520,7 @@
uart->rx_dma_buf.tail = uart->rx_dma_buf.head;
}
- spin_unlock_bh(&uart->port.lock);
- dma_enable_irq(uart->tx_dma_channel);
+ spin_unlock_bh(&uart->rx_lock);
dma_enable_irq(uart->rx_dma_channel);
mod_timer(&(uart->rx_dma_timer), jiffies + DMA_RX_FLUSH_JIFFIES);
@@ -571,7 +567,7 @@
unsigned short irqstat;
int x_pos, pos;
- spin_lock(&uart->port.lock);
+ spin_lock(&uart->rx_lock);
irqstat = get_dma_curr_irqstat(uart->rx_dma_channel);
clear_dma_irqstat(uart->rx_dma_channel);
@@ -589,7 +585,7 @@
uart->rx_dma_buf.tail = uart->rx_dma_buf.head;
}
- spin_unlock(&uart->port.lock);
+ spin_unlock(&uart->rx_lock);
return IRQ_HANDLED;
}
@@ -1332,6 +1328,7 @@
}
#ifdef CONFIG_SERIAL_BFIN_DMA
+ spin_lock_init(&uart->rx_lock);
uart->tx_done = 1;
uart->tx_count = 0;