On 10/02/2013 10:36 AM, Uwe Kleine-König wrote:
Hello Hector,
On Wed, Oct 02, 2013 at 09:31:16AM +0200, Hector Palacios wrote:
On 10/01/2013 09:48 PM, Uwe Kleine-König wrote:
Hello Hector,
On Tue, Oct 01, 2013 at 06:18:35PM +0200, Hector Palacios wrote:
The shutdown function was not waiting for the DMA buffer to flush
before disabling the AUART. This lead to many bytes not being
transferred (specially at low baudrates), as they were still in the
DMA buffer when the AUART was shutdown.
This patch also adds the check for the BUSY flag.
Signed-off-by: Hector Palacios <hector.palacios@xxxxxxxx>
---
drivers/tty/serial/mxs-auart.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index f85b8e6..0d8b2ca 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -750,12 +750,26 @@ static int mxs_auart_startup(struct uart_port *u)
return 0;
}
+static unsigned int mxs_auart_tx_empty(struct uart_port *u);
+
static void mxs_auart_shutdown(struct uart_port *u)
{
struct mxs_auart_port *s = to_auart_port(u);
+ unsigned int to;
+
+ if (auart_dma_enabled(s)) {
+ /* Wait enough time to flush DMA buffer completely */
+ to = u->timeout * UART_XMIT_SIZE / u->fifosize;
u->timeout is the time needed to send one char, right? UART_XMIT_SIZE is
the size of the circular buffer, fifosize is the size of the fifo. I
don't get what you get by dividing by the fifosize. I would have
expected something like:
u->timeout * min(UART_XMIT_SIZE, u->fifosize)
Can you explain, maybe in a comment along the code for the next person
not understanding?
u->timeout is *not* the time needed to send one char but the time
needed to flush the complete port fifo (see uart_update_timeout() in
serial_core.c where it is set).
UART_XMIT_SIZE is the number of bytes in the DMA buffer, so I divide
the max number of bytes in the FIFO by the FIFO size and multiply by
the FIFO timeout.
Another thought: Does that mean that from the framework's POV the
fifosize is UART_XMIT_SIZE instead in the DMA case? That would enable
you to just use u->timeout.
Hum, I think you hit the point.
I just saw they do this in amba_pl011.c driver:
/* The DMA buffer is now the FIFO the TTY subsystem can use */
uap->port.fifosize = PL011_DMA_BUFFER_SIZE;
I'll rework the patch and try.
Best regards,
--
Hector Palacios
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