Hi Jiada, On 07/24/2014 04:12 AM, jiwang wrote: > Hi Peter > > On 07/24/2014 01:32 AM, Peter Hurley wrote: >> Hi Dirk, >> >> On 07/23/2014 12:10 AM, Dirk Behme wrote: >>> Hi, >>> >>> this is a question regarding the i.MX6 part (drivers/tty/serial/imx.c) of the commit >>> >>> serial: Test for no tx data on tx restart >>> >>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c557d392fbf5badd693ea1946a4317c87a26a716 >>> >>> Talking with some i.MX6 experts about this, I've got the comment >>> >>> -- cut -- >>> The imx serial driver part of this commit isn't correct >>> as imx.c sends x_char in irq handler, not in imx_start_tx(), >>> -- cut -- >>> >>> What do you think? >> Thanks for the comment. >> >> Yeah, I missed that the imx driver handled x_char _at all_, >> because how the imx driver is handling x_char looks broken. >> >> For example, if data is already in the tx ring buffer, >> imx_start_tx() will send that data before the x_char, and if >> all the tx ring buffer data is sent successfully, the tx >> interrupt is switched back off, so the x_char won't be sent. > > imx_start_tx() doesn't do any actual data transfer ??? 565 static void imx_start_tx(struct uart_port *port) 566 { ... 610 611 if (readl(sport->port.membase + uts_reg(sport)) & UTS_TXEMPTY) 612 imx_transmit_buffer(sport); 613 } 463 static inline void imx_transmit_buffer(struct imx_port *sport) 464 { 465 struct circ_buf *xmit = &sport->port.state->xmit; 466 467 while (!uart_circ_empty(xmit) && 468 !(readl(sport->port.membase + uts_reg(sport)) 469 & UTS_TXFULL)) { 470 /* send xmit->buf[xmit->tail] 471 * out the port here */ 472 writel(xmit->buf[xmit->tail], sport->port.membase + URTX0); 473 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); 474 sport->port.icount.tx++; 475 } 476 477 if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) 478 uart_write_wakeup(&sport->port); 479 480 if (uart_circ_empty(xmit)) 481 imx_stop_tx(&sport->port); 482 } Regards, Peter Hurley -- 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
