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Date: Mon, 3 Aug 2015 18:09:37 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Peter Hurley <peter@...leysoftware.com>
Cc: John Ogness <john.ogness@...utronix.de>,
linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Tony Lindgren <tony@...mide.com>, linux-omap@...r.kernel.org,
nsekhar@...com, nm@...com, linux-serial@...r.kernel.org
Subject: Re: [PATCH 3/3] serial: 8250: omap: restore registers on shutdown
* Peter Hurley | 2015-07-30 20:51:10 [-0400]:
>Hi John,
Hi Peter,
>I was never really a fan of the deferred set_termios();
>I think it's more appropriate to wait for tx dma to
>complete in omap_8250_set_termios().
So you want something like this? This was only compile + boot tested
(without triggering the corner case) and I know that 8250.h piece has to
go in a separated patch (as requested in 2/3 of this series). Just checking
if this is what you had in mind.
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index c43f74c53cd9..a407757dcecc 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -42,9 +42,9 @@ struct uart_8250_dma {
size_t rx_size;
size_t tx_size;
- unsigned char tx_running:1;
- unsigned char tx_err: 1;
- unsigned char rx_running:1;
+ unsigned char tx_running;
+ unsigned char tx_err;
+ unsigned char rx_running;
};
struct old_serial_port {
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index d9a37191a1ae..12249125a218 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;
@@ -256,18 +256,6 @@ 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);
@@ -309,6 +297,7 @@ 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.
@@ -322,6 +311,7 @@ static void omap_8250_set_termios(struct uart_port *port,
struct omap8250_priv *priv = up->port.private_data;
unsigned char cval = 0;
unsigned int baud;
+ unsigned int complete_dma = 0;
switch (termios->c_cflag & CSIZE) {
case CS5:
@@ -473,6 +463,25 @@ static void omap_8250_set_termios(struct uart_port *port,
if (termios->c_iflag & IXANY)
up->mcr |= UART_MCR_XONANY;
}
+
+ if (up->dma && up->dma->tx_running) {
+ struct uart_8250_dma *dma = up->dma;
+
+ /*
+ * 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 happen.
+ */
+
+ dma->tx_running = 2;
+
+ spin_unlock_irq(&up->port.lock);
+ wait_event(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);
@@ -488,6 +497,8 @@ 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 */
@@ -869,17 +880,18 @@ 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);
@@ -899,7 +911,7 @@ 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);
}
@@ -1216,6 +1228,7 @@ 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;
Sebastian
--
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