[PATCH 05/18] Blackfin Serial Driver: fix bug - serial port transfer big file from host to target would have more lines

Bryan Wu
2009-03-06T06:46:50Z

From: Sonic Zhang <sonic.zhang@analog.com>

Ignore receiving data if new position is in the same line of
current buffer tail and small.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
---
drivers/serial/bfin_5xx.c | 31 +++++++++++++++++++++++++++++--
1 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index 8d34ccd..5a163f6 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -407,6 +407,15 @@ 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;
@@ -417,7 +426,11 @@ 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;
@@ -455,11 +468,25 @@ 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;
--
1.5.6.3