Re: [RFC/PATCH 10/13] serial: omap: stick to put_autosuspend

[Felipe Balbi]

Hi,

On Tue, Aug 21, 2012 at 02:02:46PM +0300, Felipe Balbi wrote:
> On Tue, Aug 21, 2012 at 04:35:26PM +0530, Shilimkar, Santosh wrote:
> > On Tue, Aug 21, 2012 at 4:27 PM, Felipe Balbi <balbi@xxxxxx> wrote:
> > > On Tue, Aug 21, 2012 at 04:12:11PM +0530, Shilimkar, Santosh wrote:
> > >> On Tue, Aug 21, 2012 at 2:45 PM, Felipe Balbi <balbi@xxxxxx> wrote:
> > >> > Everytime we're done using our TTY, we want
> > >> > the pm timer to be reinitilized. By sticking
> > >> > to pm_runtime_pm_autosuspend() we make sure
> > >> > that this will always be the case.
> > >> >
> > >> > Signed-off-by: Felipe Balbi <balbi@xxxxxx>
> > >> > ---
> > >> >  drivers/tty/serial/omap-serial.c | 33 ++++++++++++++++++++++-----------
> > >> >  1 file changed, 22 insertions(+), 11 deletions(-)
> > >> >
> > >> > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> > >> > index 6ea24c5..458d77c 100644
> > >> > --- a/drivers/tty/serial/omap-serial.c
> > >> > +++ b/drivers/tty/serial/omap-serial.c
> > >> > @@ -164,7 +164,8 @@ static void serial_omap_enable_ms(struct uart_port *port)
> > >> >         pm_runtime_get_sync(up->dev);
> > >> >         up->ier |= UART_IER_MSI;
> > >> >         serial_out(up, UART_IER, up->ier);
> > >> > -       pm_runtime_put(up->dev);
> > >> > +       pm_runtime_mark_last_busy(up->dev);
> > >> > +       pm_runtime_put_autosuspend(up->dev);
> > >> >  }
> > >> >
> > >> Can you please expand the change-log a bit ?
> > >> Didn't follow the time re-init part completely.
> > >
> > > It's really just a micro-optimization. The thing is:
> > >
> > > if I call pm_runtime_put(), I will not reinitialize the pm timer to
> > > whatever timeout value I used. This means that pm_runtime_put() could
> > > actually execute right away (if timer was about to expire when I called
> > > pm_runtime_put()). While this wouldn't cause any issues, it's better to
> > > reinitialize the timer and make sure if there's another
> > > read/write/set_termios/whatever coming right after this, UART is still
> > > powered up.
> > >
> > > I mean, it's really just trying to avoid context save & restore when
> > > UART is still under heavy usage.
> > >
> > > Does it make sense ?
> > 
> > It does. Would be good to add the above description in the change-log.
> > Thanks for clarification.
> 
> will do, cheers

I have updated my branch like below. Will wait for any other comments
before sending another version.

commit 8ff7ab777d2bf8619328ddd43ddf2f8660dd011f
Author: Felipe Balbi <balbi@xxxxxx>
Date:   Tue Aug 21 11:45:47 2012 +0300

    serial: omap: stick to put_autosuspend
    
    Everytime we're done using our TTY, we want
    the pm timer to be reinitilized. By sticking
    to pm_runtime_pm_autosuspend() we make sure
    that this will always be the case.
    
    The idea behind this patch is to make sure we
    will always reinitialize the pm timer so that
    we don't fall into a situation where pm_runtime_put()
    expires right away (if timer was already about to
    expire when we made the call to pm_runtime_put()).
    
    While suspending right away wouldn't cause any
    issues, reinitializing the pm timer can help us
    avoiding unnecessary context save & restore
    operations (which are somewhat expensive) if there's
    another read/write/set_termios request coming right
    after. IOW, we are trying to make sure UART is still
    powered up while it's still under heavy usage.
    
    Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
    Signed-off-by: Felipe Balbi <balbi@xxxxxx>

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 6ea24c5..458d77c 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -164,7 +164,8 @@ static void serial_omap_enable_ms(struct uart_port *port)
 	pm_runtime_get_sync(up->dev);
 	up->ier |= UART_IER_MSI;
 	serial_out(up, UART_IER, up->ier);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static void serial_omap_stop_tx(struct uart_port *port)
@@ -412,7 +413,8 @@ static unsigned int serial_omap_tx_empty(struct uart_port *port)
 	spin_lock_irqsave(&up->port.lock, flags);
 	ret = serial_in(up, UART_LSR) & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	return ret;
 }
 
@@ -424,7 +426,8 @@ static unsigned int serial_omap_get_mctrl(struct uart_port *port)
 
 	pm_runtime_get_sync(up->dev);
 	status = check_modem_status(up);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 
 	dev_dbg(up->port.dev, "serial_omap_get_mctrl+%d\n", up->port.line);
 
@@ -460,7 +463,8 @@ static void serial_omap_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	up->mcr = serial_in(up, UART_MCR);
 	up->mcr |= mcr;
 	serial_out(up, UART_MCR, up->mcr);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static void serial_omap_break_ctl(struct uart_port *port, int break_state)
@@ -477,7 +481,8 @@ static void serial_omap_break_ctl(struct uart_port *port, int break_state)
 		up->lcr &= ~UART_LCR_SBC;
 	serial_out(up, UART_LCR, up->lcr);
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static int serial_omap_startup(struct uart_port *port)
@@ -575,7 +580,8 @@ static void serial_omap_shutdown(struct uart_port *port)
 	if (serial_in(up, UART_LSR) & UART_LSR_DR)
 		(void) serial_in(up, UART_RX);
 
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	free_irq(up->port.irq, up);
 }
 
@@ -846,7 +852,8 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
 	serial_omap_configure_xonxoff(up, termios);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	dev_dbg(up->port.dev, "serial_omap_set_termios+%d\n", up->port.line);
 }
 
@@ -877,7 +884,8 @@ serial_omap_pm(struct uart_port *port, unsigned int state,
 			pm_runtime_allow(up->dev);
 	}
 
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static void serial_omap_release_port(struct uart_port *port)
@@ -959,7 +967,8 @@ static void serial_omap_poll_put_char(struct uart_port *port, unsigned char ch)
 	pm_runtime_get_sync(up->dev);
 	wait_for_xmitr(up);
 	serial_out(up, UART_TX, ch);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 }
 
 static int serial_omap_poll_get_char(struct uart_port *port)
@@ -973,7 +982,8 @@ static int serial_omap_poll_get_char(struct uart_port *port)
 		return NO_POLL_CHAR;
 
 	status = serial_in(up, UART_RX);
-	pm_runtime_put(up->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	return status;
 }
 
@@ -1305,7 +1315,8 @@ static int serial_omap_probe(struct platform_device *pdev)
 	if (ret != 0)
 		goto err_add_port;
 
-	pm_runtime_put(&pdev->dev);
+	pm_runtime_mark_last_busy(up->dev);
+	pm_runtime_put_autosuspend(up->dev);
 	platform_set_drvdata(pdev, up);
 	return 0;
 

let me know if your Ack is still valid.

-- 
balbi

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