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.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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