Using only 4 DMA periods for UART RX is very few if we have a high
frequency of small transfers - like in our case using Bluetooth with
many small packets via UART - causing many dma transfers but in each
only filling a fraction of a single buffer. Such a case may lead to
the situation that DMA RX transfer is triggered but no free buffer is
available. While we have addressed the dma handling already with
"dmaengine: imx-sdma: fix dma freezes" we still want to avoid
UART RX FIFO overrun. So we decrease the size of the buffers and
increase their number and the total buffer size.
Signed-off-by: Philipp Puschmann <philipp.puschmann@xxxxxxxxx>
Reviewed-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
Changelog v2:
- split this patch from series "Fix UART DMA freezes for iMX6"
- add Reviewed-by tag
drivers/tty/serial/imx.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 87c58f9f6390..51dc19833eab 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1034,8 +1034,6 @@ static void imx_uart_timeout(struct timer_list *t)
}
}
-#define RX_BUF_SIZE (PAGE_SIZE)
-
/*
* There are two kinds of RX DMA interrupts(such as in the MX6Q):
* [1] the RX DMA buffer is full.
@@ -1118,7 +1116,8 @@ static void imx_uart_dma_rx_callback(void *data)
}
/* RX DMA buffer periods */
-#define RX_DMA_PERIODS 4
+#define RX_DMA_PERIODS 16
+#define RX_BUF_SIZE (PAGE_SIZE / 4)
static int imx_uart_start_rx_dma(struct imx_port *sport)
{
--
2.23.0
