Re: [PATCH 3/6] tty: serial: 8250 core: add runtime pm

[Mika Westerberg]

On Wed, Jul 09, 2014 at 07:49:34PM +0200, Sebastian Andrzej Siewior wrote:
> While comparing the OMAP-serial and the 8250 part of this I noticed that
> the the latter does not use runtime-pm. Here are the pieces. It is
> basically a get before first register access and a last_busy + put after
> last access.
> If I understand this correct, it should do nothing as long as
> pm_runtime_use_autosuspend() + pm_runtime_enable() isn't invoked on the
> device.
> 
> Cc: mika.westerberg@xxxxxxxxxxxxxxx

Sorry for the delay, just came back from vacation.

Adding Heikki, who knows the 8250_dw driver much better than me.
Unfortunately he is still on vacation for next two weeks.

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
>  drivers/tty/serial/8250/8250_core.c | 101 +++++++++++++++++++++++++++++++-----
>  1 file changed, 88 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index d37eb08..1a91a89 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -38,6 +38,7 @@
>  #include <linux/nmi.h>
>  #include <linux/mutex.h>
>  #include <linux/slab.h>
> +#include <linux/pm_runtime.h>
>  #ifdef CONFIG_SPARC
>  #include <linux/sunserialcore.h>
>  #endif
> @@ -553,10 +554,11 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
>  	 * offset but the UART channel may only write to the corresponding
>  	 * bit.
>  	 */
> +	pm_runtime_get_sync(p->port.dev);
>  	if ((p->port.type == PORT_XR17V35X) ||
>  	   (p->port.type == PORT_XR17D15X)) {
>  		serial_out(p, UART_EXAR_SLEEP, sleep ? 0xff : 0);
> -		return;
> +		goto out;
>  	}
>  
>  	if (p->capabilities & UART_CAP_SLEEP) {
> @@ -571,7 +573,17 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
>  			serial_out(p, UART_EFR, 0);
>  			serial_out(p, UART_LCR, 0);
>  		}
> +
> +		if (!device_may_wakeup(p->port.dev)) {
> +			if (sleep)
> +				pm_runtime_forbid(p->port.dev);
> +			else
> +				pm_runtime_allow(p->port.dev);
> +		}
>  	}
> +out:
> +	pm_runtime_mark_last_busy(p->port.dev);
> +	pm_runtime_put_autosuspend(p->port.dev);
>  }
>  
>  #ifdef CONFIG_SERIAL_8250_RSA
> @@ -1280,6 +1292,7 @@ static void serial8250_stop_tx(struct uart_port *port)
>  	struct uart_8250_port *up =
>  		container_of(port, struct uart_8250_port, port);
>  
> +	pm_runtime_get_sync(port->dev);
>  	__stop_tx(up);
>  
>  	/*
> @@ -1289,6 +1302,8 @@ static void serial8250_stop_tx(struct uart_port *port)
>  		up->acr |= UART_ACR_TXDIS;
>  		serial_icr_write(up, UART_ACR, up->acr);
>  	}
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  static void serial8250_start_tx(struct uart_port *port)
> @@ -1296,8 +1311,9 @@ static void serial8250_start_tx(struct uart_port *port)
>  	struct uart_8250_port *up =
>  		container_of(port, struct uart_8250_port, port);
>  
> +	pm_runtime_get_sync(port->dev);
>  	if (up->dma && !serial8250_tx_dma(up)) {
> -		return;
> +		goto out;
>  	} else if (!(up->ier & UART_IER_THRI)) {
>  		up->ier |= UART_IER_THRI;
>  		serial_port_out(port, UART_IER, up->ier);
> @@ -1318,6 +1334,9 @@ static void serial8250_start_tx(struct uart_port *port)
>  		up->acr &= ~UART_ACR_TXDIS;
>  		serial_icr_write(up, UART_ACR, up->acr);
>  	}
> +out:
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  static void serial8250_stop_rx(struct uart_port *port)
> @@ -1325,9 +1344,14 @@ static void serial8250_stop_rx(struct uart_port *port)
>  	struct uart_8250_port *up =
>  		container_of(port, struct uart_8250_port, port);
>  
> +	pm_runtime_get_sync(port->dev);
> +
>  	up->ier &= ~UART_IER_RLSI;
>  	up->port.read_status_mask &= ~UART_LSR_DR;
>  	serial_port_out(port, UART_IER, up->ier);
> +
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  static void serial8250_enable_ms(struct uart_port *port)
> @@ -1340,7 +1364,10 @@ static void serial8250_enable_ms(struct uart_port *port)
>  		return;
>  
>  	up->ier |= UART_IER_MSI;
> +	pm_runtime_get_sync(port->dev);
>  	serial_port_out(port, UART_IER, up->ier);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  /*
> @@ -1530,9 +1557,17 @@ EXPORT_SYMBOL_GPL(serial8250_handle_irq);
>  
>  static int serial8250_default_handle_irq(struct uart_port *port)
>  {
> -	unsigned int iir = serial_port_in(port, UART_IIR);
> +	unsigned int iir;
> +	int ret;
>  
> -	return serial8250_handle_irq(port, iir);
> +	pm_runtime_get_sync(port->dev);

Is this function executed in interrupt context? Calling _sync() variant
might sleep here. At least if the RTPM of the device is backed by ACPI
methods.

> +
> +	iir = serial_port_in(port, UART_IIR);
> +	ret = serial8250_handle_irq(port, iir);
> +
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
> +	return ret;
>  }
>  
>  /*
> @@ -1790,11 +1825,16 @@ static unsigned int serial8250_tx_empty(struct uart_port *port)
>  	unsigned long flags;
>  	unsigned int lsr;
>  
> +	pm_runtime_get_sync(port->dev);
> +
>  	spin_lock_irqsave(&port->lock, flags);
>  	lsr = serial_port_in(port, UART_LSR);
>  	up->lsr_saved_flags |= lsr & LSR_SAVE_FLAGS;
>  	spin_unlock_irqrestore(&port->lock, flags);
>  
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
> +
>  	return (lsr & BOTH_EMPTY) == BOTH_EMPTY ? TIOCSER_TEMT : 0;
>  }
>  
> @@ -1805,7 +1845,10 @@ static unsigned int serial8250_get_mctrl(struct uart_port *port)
>  	unsigned int status;
>  	unsigned int ret;
>  
> +	pm_runtime_get_sync(port->dev);
>  	status = serial8250_modem_status(up);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  
>  	ret = 0;
>  	if (status & UART_MSR_DCD)
> @@ -1838,7 +1881,10 @@ static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
>  
>  	mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr;
>  
> +	pm_runtime_get_sync(port->dev);
>  	serial_port_out(port, UART_MCR, mcr);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  static void serial8250_break_ctl(struct uart_port *port, int break_state)
> @@ -1847,6 +1893,7 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state)
>  		container_of(port, struct uart_8250_port, port);
>  	unsigned long flags;
>  
> +	pm_runtime_get_sync(port->dev);
>  	spin_lock_irqsave(&port->lock, flags);
>  	if (break_state == -1)
>  		up->lcr |= UART_LCR_SBC;
> @@ -1854,6 +1901,8 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state)
>  		up->lcr &= ~UART_LCR_SBC;
>  	serial_port_out(port, UART_LCR, up->lcr);
>  	spin_unlock_irqrestore(&port->lock, flags);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  }
>  
>  /*
> @@ -1898,12 +1947,23 @@ static void wait_for_xmitr(struct uart_8250_port *up, int bits)
>  
>  static int serial8250_get_poll_char(struct uart_port *port)
>  {
> -	unsigned char lsr = serial_port_in(port, UART_LSR);
> +	unsigned char lsr;
> +	int status;
> +
> +	pm_runtime_get_sync(port->dev);
>  
> -	if (!(lsr & UART_LSR_DR))
> -		return NO_POLL_CHAR;
> +	lsr = serial_port_in(port, UART_LSR);
>  
> -	return serial_port_in(port, UART_RX);
> +	if (!(lsr & UART_LSR_DR)) {
> +		status = NO_POLL_CHAR;
> +		goto out;
> +	}
> +
> +	status = serial_port_in(port, UART_RX);
> +out:
> +	pm_runtime_mark_last_busy(up->dev);
> +	pm_runtime_put_autosuspend(up->dev);
> +	return status;
>  }
>  
>  
> @@ -1914,6 +1974,7 @@ static void serial8250_put_poll_char(struct uart_port *port,
>  	struct uart_8250_port *up =
>  		container_of(port, struct uart_8250_port, port);
>  
> +	pm_runtime_get_sync(up->dev);
>  	/*
>  	 *	First save the IER then disable the interrupts
>  	 */
> @@ -1935,6 +1996,9 @@ static void serial8250_put_poll_char(struct uart_port *port,
>  	 */
>  	wait_for_xmitr(up, BOTH_EMPTY);
>  	serial_port_out(port, UART_IER, ier);
> +	pm_runtime_mark_last_busy(up->dev);
> +	pm_runtime_put_autosuspend(up->dev);
> +
>  }
>  
>  #endif /* CONFIG_CONSOLE_POLL */
> @@ -1961,6 +2025,7 @@ int serial8250_do_startup(struct uart_port *port)
>  	if (port->iotype != up->cur_iotype)
>  		set_io_from_upio(port);
>  
> +	pm_runtime_get_sync(port->dev);
>  	if (port->type == PORT_16C950) {
>  		/* Wake up and initialize UART */
>  		up->acr = 0;
> @@ -1981,7 +2046,6 @@ int serial8250_do_startup(struct uart_port *port)
>  	 */
>  	enable_rsa(up);
>  #endif
> -
>  	/*
>  	 * Clear the FIFO buffers and disable them.
>  	 * (they will be reenabled in set_termios())
> @@ -2005,7 +2069,8 @@ int serial8250_do_startup(struct uart_port *port)
>  	    (serial_port_in(port, UART_LSR) == 0xff)) {
>  		printk_ratelimited(KERN_INFO "ttyS%d: LSR safety check engaged!\n",
>  				   serial_index(port));
> -		return -ENODEV;
> +		retval = -ENODEV;
> +		goto out;
>  	}
>  
>  	/*
> @@ -2090,7 +2155,7 @@ int serial8250_do_startup(struct uart_port *port)
>  	} else {
>  		retval = serial_link_irq_chain(up);
>  		if (retval)
> -			return retval;
> +			goto out;
>  	}
>  
>  	/*
> @@ -2188,8 +2253,11 @@ int serial8250_do_startup(struct uart_port *port)
>  		outb_p(0x80, icp);
>  		inb_p(icp);
>  	}
> -
> -	return 0;
> +	retval = 0;
> +out:
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
> +	return retval;
>  }
>  EXPORT_SYMBOL_GPL(serial8250_do_startup);
>  
> @@ -2207,6 +2275,7 @@ void serial8250_do_shutdown(struct uart_port *port)
>  		container_of(port, struct uart_8250_port, port);
>  	unsigned long flags;
>  
> +	pm_runtime_get_sync(port->dev);
>  	/*
>  	 * Disable interrupts from this port
>  	 */
> @@ -2246,6 +2315,8 @@ void serial8250_do_shutdown(struct uart_port *port)
>  	 * the IRQ chain.
>  	 */
>  	serial_port_in(port, UART_RX);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
>  
>  	del_timer_sync(&up->timer);
>  	up->timer.function = serial8250_timeout;
> @@ -2365,6 +2436,7 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  	 * Ok, we're now changing the port state.  Do it with
>  	 * interrupts disabled.
>  	 */
> +	pm_runtime_get_sync(port->dev);
>  	spin_lock_irqsave(&port->lock, flags);
>  
>  	/*
> @@ -2486,6 +2558,9 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
>  	}
>  	serial8250_set_mctrl(port, port->mctrl);
>  	spin_unlock_irqrestore(&port->lock, flags);
> +	pm_runtime_mark_last_busy(port->dev);
> +	pm_runtime_put_autosuspend(port->dev);
> +
>  	/* Don't rewrite B0 */
>  	if (tty_termios_baud_rate(termios))
>  		tty_termios_encode_baud_rate(termios, baud, baud);
> -- 
> 2.0.1
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