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Subject[RFC PATCH 3/4] tty: serial: 8250 core: add runtime pm
Date
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.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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 f731fff..b0b9abb 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);
+
+ 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 @@ static void serial8250_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 @@ static void serial8250_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;
@@ -2356,6 +2427,7 @@ 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);

/*
@@ -2477,6 +2549,9 @@ 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);
--
2.0.0


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