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? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
