From: Sebastian Andrzej Siewior <[email protected]> It has been observed that the TX-DMA can stall if termios changes occur while a TX-DMA operation is in progress. Previously this was handled by allowing set_termios to return immediately and deferring the change until the operation is completed. Now set_termios will block until the operation is completed, proceed with the changes, then schedule any pending next operation.
Commit message and forward port by John Ogness. Tested-by: John Ogness <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- Patch against next-20160331. drivers/tty/serial/8250/8250_omap.c | 57 ++++++++++++++++---------- 1 file changed, 37 insertions(+), 20 deletions(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 6f76051..9459b4d 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -100,9 +100,9 @@ struct omap8250_priv { u8 wer; u8 xon; u8 xoff; - u8 delayed_restore; u16 quot; + wait_queue_head_t termios_wait; bool is_suspending; int wakeirq; int wakeups_enabled; @@ -257,18 +257,6 @@ static void omap8250_update_mdr1(struct uart_8250_port *up, static void omap8250_restore_regs(struct uart_8250_port *up) { struct omap8250_priv *priv = up->port.private_data; - struct uart_8250_dma *dma = up->dma; - - if (dma && dma->tx_running) { - /* - * TCSANOW requests the change to occur immediately however if - * we have a TX-DMA operation in progress then it has been - * observed that it might stall and never complete. Therefore we - * delay DMA completes to prevent this hang from happen. - */ - priv->delayed_restore = 1; - return; - } serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B); serial_out(up, UART_EFR, UART_EFR_ECB); @@ -310,6 +298,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up) up->port.ops->set_mctrl(&up->port, up->port.mctrl); } +static void omap_8250_dma_tx_complete(void *param); /* * OMAP can use "CLK / (16 or 13) / div" for baud rate. And then we have have * some differences in how we want to handle flow control. @@ -320,6 +309,8 @@ static void omap_8250_set_termios(struct uart_port *port, { struct uart_8250_port *up = up_to_u8250p(port); struct omap8250_priv *priv = up->port.private_data; + struct uart_8250_dma *dma = up->dma; + unsigned int complete_dma = 0; unsigned char cval = 0; unsigned int baud; @@ -430,7 +421,7 @@ static void omap_8250_set_termios(struct uart_port *port, priv->scr = OMAP_UART_SCR_RX_TRIG_GRANU1_MASK | OMAP_UART_SCR_TX_EMPTY | OMAP_UART_SCR_TX_TRIG_GRANU1_MASK; - if (up->dma) + if (dma) priv->scr |= OMAP_UART_SCR_DMAMODE_1 | OMAP_UART_SCR_DMAMODE_CTL; @@ -460,6 +451,24 @@ static void omap_8250_set_termios(struct uart_port *port, priv->efr |= OMAP_UART_SW_TX; } } + + if (dma && dma->tx_running) { + /* + * TCSANOW requests the change to occur immediately, however + * if we have a TX-DMA operation in progress then it has been + * observed that it might stall and never complete. Therefore + * we wait until DMA completes to prevent this hang from + * happening. + */ + + dma->tx_running = 2; + + spin_unlock_irq(&up->port.lock); + wait_event_interruptible(priv->termios_wait, + dma->tx_running == 3); + spin_lock_irq(&up->port.lock); + complete_dma = 1; + } omap8250_restore_regs(up); spin_unlock_irq(&up->port.lock); @@ -475,6 +484,8 @@ static void omap_8250_set_termios(struct uart_port *port, /* Don't rewrite B0 */ if (tty_termios_baud_rate(termios)) tty_termios_encode_baud_rate(termios, baud, baud); + if (complete_dma) + omap_8250_dma_tx_complete(up); } /* same as 8250 except that we may have extra flow bits set in EFR */ @@ -893,17 +904,18 @@ static void omap_8250_dma_tx_complete(void *param) spin_lock_irqsave(&p->port.lock, flags); + if (dma->tx_running == 2) { + dma->tx_running = 3; + wake_up(&priv->termios_wait); + goto out; + } + dma->tx_running = 0; xmit->tail += dma->tx_size; xmit->tail &= UART_XMIT_SIZE - 1; p->port.icount.tx += dma->tx_size; - if (priv->delayed_restore) { - priv->delayed_restore = 0; - omap8250_restore_regs(p); - } - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) uart_write_wakeup(&p->port); @@ -923,7 +935,7 @@ static void omap_8250_dma_tx_complete(void *param) p->ier |= UART_IER_THRI; serial_port_out(&p->port, UART_IER, p->ier); } - +out: spin_unlock_irqrestore(&p->port.lock, flags); } @@ -1088,6 +1100,10 @@ static inline int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir) { return -EINVAL; } + +static void omap_8250_dma_tx_complete(void *param) +{ +} #endif static int omap8250_no_handle_irq(struct uart_port *port) @@ -1241,6 +1257,7 @@ static int omap8250_probe(struct platform_device *pdev) priv->omap8250_dma.rx_size = RX_TRIGGER; priv->omap8250_dma.rxconf.src_maxburst = RX_TRIGGER; priv->omap8250_dma.txconf.dst_maxburst = TX_TRIGGER; + init_waitqueue_head(&priv->termios_wait); if (of_machine_is_compatible("ti,am33xx")) priv->habit |= OMAP_DMA_TX_KICK; -- 1.7.10.4
