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Message-ID: <8737r7ght7.fsf@linutronix.de>
Date: Thu, 31 Mar 2016 10:41:56 +0200
From: John Ogness <john.ogness@...utronix.de>
To: Peter Hurley <peter@...leysoftware.com>
Cc: linux-omap@...r.kernel.org
Subject: [PATCH] tty: serial: 8250_omap: do not defer termios changes
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
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 <john.ogness@...utronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
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
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