Hi Uwe,
On 10/02/2013 10:30 AM, Uwe Kleine-König wrote:
Hello Hector,
On Wed, Oct 02, 2013 at 10:09:10AM +0200, Hector Palacios wrote:
On 10/02/2013 09:44 AM, Uwe Kleine-König wrote:
On Wed, Oct 02, 2013 at 09:31:16AM +0200, Hector Palacios wrote:
On 10/01/2013 09:48 PM, Uwe Kleine-König wrote:
On Tue, Oct 01, 2013 at 06:18:35PM +0200, Hector Palacios wrote:
+ /* 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).
Ah, right. (BTW, uart_update_timeout should better round up instead of
round down, i.e.
- port->timeout = (HZ * bits) / baud + HZ/50;
+ port->timeout = DIV_ROUND_UP(HZ * bits, baud) + HZ/50;
)
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.
ditto here, better round up. Although I think using a completion could
shorten the timeout considerably because there are often less than
UART_XMIT_SIZE chars in the buffer?!
I'm not really waiting the full timeout. I'm checking for TX fifo
empty every 1ms and for a maximum of 'to' ms.
Correct. Still using DIV_ROUND_UP would be better, right?
I think it is not really needed, after all the code is adding HZ/50 of slop which acts
like a round up, doesn't it?
/*
* Figure the timeout to send the above number of bits.
* Add .02 seconds of slop
*/
port->timeout = (HZ * bits) / baud + HZ/50;
Best regards,
--
Hector Palacios
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