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authorSonic Zhang <sonic.zhang@analog.com>2009-06-11 13:38:16 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-11 08:51:04 -0700
commit8516c568f25666a012ec4c859e640a76fc9b6ec0 (patch)
treef2d72c684c5f8c726f752643bdd88268df836b5b /drivers/serial
parent4328e3e5ef1ae3427a4f6863aa65916a68ec2dd9 (diff)
Blackfin Serial Driver: fix error while transferring large files
Ignore receiving data if new position is in the same line of current buffer tail and is small. This should decrease overruns. Signed-off-by: Sonic Zhang <sonic.zhang@analog.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org> Signed-off-by: Bryan Wu <cooloney@kernel.org> Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/serial')
-rw-r--r--drivers/serial/bfin_5xx.c31
1 files changed, 29 insertions, 2 deletions
diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index d86123e03391..65a4c07f6199 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -477,6 +477,15 @@ void bfin_serial_rx_dma_timeout(struct bfin_serial_port *uart)
spin_lock_irqsave(&uart->port.lock, flags);
+ /* 2D DMA RX buffer ring is used. Because curr_y_count and
+ * curr_x_count can't be read as an atomic operation,
+ * curr_y_count should be read before curr_x_count. When
+ * curr_x_count is read, curr_y_count may already indicate
+ * next buffer line. But, the position calculated here is
+ * still indicate the old line. The wrong position data may
+ * be smaller than current buffer tail, which cause garbages
+ * are received if it is not prohibit.
+ */
uart->rx_dma_nrows = get_dma_curr_ycount(uart->rx_dma_channel);
x_pos = get_dma_curr_xcount(uart->rx_dma_channel);
uart->rx_dma_nrows = DMA_RX_YCOUNT - uart->rx_dma_nrows;
@@ -487,7 +496,11 @@ void bfin_serial_rx_dma_timeout(struct bfin_serial_port *uart)
x_pos = 0;
pos = uart->rx_dma_nrows * DMA_RX_XCOUNT + x_pos;
- if (pos != uart->rx_dma_buf.tail) {
+ /* Ignore receiving data if new position is in the same line of
+ * current buffer tail and small.
+ */
+ if (pos > uart->rx_dma_buf.tail ||
+ uart->rx_dma_nrows < (uart->rx_dma_buf.tail/DMA_RX_XCOUNT)) {
uart->rx_dma_buf.head = pos;
bfin_serial_dma_rx_chars(uart);
uart->rx_dma_buf.tail = uart->rx_dma_buf.head;
@@ -532,11 +545,25 @@ static irqreturn_t bfin_serial_dma_rx_int(int irq, void *dev_id)
{
struct bfin_serial_port *uart = dev_id;
unsigned short irqstat;
+ int pos;
spin_lock(&uart->port.lock);
irqstat = get_dma_curr_irqstat(uart->rx_dma_channel);
clear_dma_irqstat(uart->rx_dma_channel);
- bfin_serial_dma_rx_chars(uart);
+
+ uart->rx_dma_nrows = get_dma_curr_ycount(uart->rx_dma_channel);
+ uart->rx_dma_nrows = DMA_RX_YCOUNT - uart->rx_dma_nrows;
+ if (uart->rx_dma_nrows == DMA_RX_YCOUNT)
+ uart->rx_dma_nrows = 0;
+
+ pos = uart->rx_dma_nrows * DMA_RX_XCOUNT;
+ if (pos > uart->rx_dma_buf.tail ||
+ uart->rx_dma_nrows < (uart->rx_dma_buf.tail/DMA_RX_XCOUNT)) {
+ uart->rx_dma_buf.head = pos;
+ bfin_serial_dma_rx_chars(uart);
+ uart->rx_dma_buf.tail = uart->rx_dma_buf.head;
+ }
+
spin_unlock(&uart->port.lock);
return IRQ_HANDLED;