@@ -1173,16 +1173,6 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
return 0;
}
- sg_init_table(&sg, 1);
- ret = kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, &sg, 1,
- UART_XMIT_SIZE, dma->tx_addr);
- if (ret != 1) {
- serial8250_clear_THRI(p);
- return 0;
- }
-
- dma->tx_size = sg_dma_len(&sg);
-
if (priv->habit & OMAP_DMA_TX_KICK) {
unsigned char c;
u8 tx_lvl;
@@ -1207,7 +1197,7 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
ret = -EBUSY;
goto err;
}
- if (dma->tx_size < 4) {
+ if (kfifo_len(&tport->xmit_fifo) < 4) {
ret = -EINVAL;
goto err;
}
@@ -1216,11 +1206,12 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
goto err;
}
skip_byte = c;
- /* now we need to recompute due to kfifo_get */
- kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, &sg, 1,
- UART_XMIT_SIZE, dma->tx_addr);
}
+ sg_init_table(&sg, 1);
+ kfifo_dma_out_prepare_mapped(&tport->xmit_fifo, &sg, 1,
+ UART_XMIT_SIZE, dma->tx_addr);
+
desc = dmaengine_prep_slave_sg(dma->txchan, &sg, 1, DMA_MEM_TO_DEV,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc) {
@@ -1228,6 +1219,7 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
goto err;
}
+ dma->tx_size = sg_dma_len(&sg);
dma->tx_running = 1;
desc->callback = omap_8250_dma_tx_complete;
@@ -1248,8 +1240,10 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
err:
dma->tx_err = 1;
out_skip:
- if (skip_byte >= 0)
+ if (skip_byte >= 0) {
serial_out(p, UART_TX, skip_byte);
+ p->port.icount.tx++;
+ }
return ret;
}
Commit 1788cf6a91d9 ("tty: serial: switch from circ_buf to kfifo") introduced an error in the TX DMA handling for 8250_omap. When the OMAP_DMA_TX_KICK flag is set, one byte is pulled from the kfifo and emitted directly in order to start the DMA. This is done without updating DMA tx_size which leads to uart_xmit_advance() called in the DMA complete callback advancing the kfifo by one too much. In practice, transmitting N bytes has been seen to result in the last N-1 bytes being sent repeatedly. This change fixes the problem by moving all of the dma setup after the OMAP_DMA_TX_KICK handling and using kfifo_len() instead of the dma size for the 4-byte cutoff check. This slightly changes the behaviour at buffer wraparound, but it still transmits the correct bytes somehow. At the point kfifo_dma_out_prepare_mapped is called, at least one byte is guaranteed to be in the fifo, so checking the return value is not necessary. Fixes: 1788cf6a91d9 ("tty: serial: switch from circ_buf to kfifo") Cc: stable@vger.kernel.org Signed-off-by: Mans Rullgard <mans@mansr.com> --- v2: split patch in two --- drivers/tty/serial/8250/8250_omap.c | 24 +++++++++--------------- 1 file changed, 9 insertions(+), 15 deletions(-)