| Message ID | 20211115084203.56478-5-tony@atomide.com |
|---|---|
| State | New |
| Headers | show |
| Series | Serial port generic PM to fix 8250 PM | expand |
On Mon, Nov 15, 2021 at 10:42:00AM +0200, Tony Lindgren wrote: > We can use the wakeup() and uart_start_pending_tx() calls to wake up an > idle serial port and send out the pending TX buffer on runtime PM resume. > This allows us to remove the dependency to pm_runtime_irq_safe() for > 8250_omap driver in the following patches. > > We manage the port runtime_suspended flag in the serial port driver as > only the driver knows when the hardware is runtime PM suspended. Note that > The current flag for rpm_tx_active cannot be used as it is TX specific > for 8250_port. > > We already have serial8250_start_tx() call serial8250_rpm_get_tx(), and > serial8250_stop_tx() call serial8250_rpm_put_tx() to take care of the > runtime PM usage count for TX. To have the serial port driver call > uart_start_pending_tx() on runtime resume, we must now use just > pm_runtime_get() for serial8250_start_tx() instead of the sync version. > > With these changes we must now also flip the 8250_omap driver over to > call uart_start_pending_tx(). That's currently the only user of > UART_CAP_RPM. > > Signed-off-by: Tony Lindgren <tony@atomide.com> > --- > drivers/tty/serial/8250/8250_omap.c | 19 ++++++++++++++ > drivers/tty/serial/8250/8250_port.c | 39 ++++++++++++++++++++++++++++- > 2 files changed, 57 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c > --- a/drivers/tty/serial/8250/8250_omap.c > +++ b/drivers/tty/serial/8250/8250_omap.c > @@ -1593,12 +1593,16 @@ static int omap8250_runtime_suspend(struct device *dev) > { > struct omap8250_priv *priv = dev_get_drvdata(dev); > struct uart_8250_port *up; > + struct uart_port *port; > + unsigned long flags; > > /* In case runtime-pm tries this before we are setup */ > if (!priv) > return 0; > > up = serial8250_get_port(priv->line); > + port = &up->port; > + > /* > * When using 'no_console_suspend', the console UART must not be > * suspended. Since driver suspend is managed by runtime suspend, > @@ -1610,6 +1614,10 @@ static int omap8250_runtime_suspend(struct device *dev) > return -EBUSY; > } > > + spin_lock_irqsave(&port->lock, flags); > + port->runtime_suspended = 1; > + spin_unlock_irqrestore(&port->lock, flags); > + > if (priv->habit & UART_ERRATA_CLOCK_DISABLE) { > int ret; > > @@ -1636,13 +1644,18 @@ static int omap8250_runtime_resume(struct device *dev) > { > struct omap8250_priv *priv = dev_get_drvdata(dev); > struct uart_8250_port *up; > + struct uart_port *port; > + unsigned long flags; > > /* In case runtime-pm tries this before we are setup */ > if (!priv) > return 0; > > up = serial8250_get_port(priv->line); > + port = &up->port; > > + /* Restore state with interrupts disabled */ > + spin_lock_irqsave(&port->lock, flags); > if (omap8250_lost_context(up)) > omap8250_restore_regs(up); > > @@ -1651,6 +1664,12 @@ static int omap8250_runtime_resume(struct device *dev) > > priv->latency = priv->calc_latency; > schedule_work(&priv->qos_work); > + > + port->runtime_suspended = 0; > + spin_unlock_irqrestore(&port->lock, flags); > + > + uart_start_pending_tx(port); > + > return 0; > } > #endif > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -724,7 +724,7 @@ void serial8250_rpm_get_tx(struct uart_8250_port *p) > rpm_active = xchg(&p->rpm_tx_active, 1); > if (rpm_active) > return; > - pm_runtime_get_sync(p->port.dev); > + pm_runtime_get(p->port.dev); > } > EXPORT_SYMBOL_GPL(serial8250_rpm_get_tx); > > @@ -2509,6 +2509,42 @@ static void serial8250_shutdown(struct uart_port *port) > serial8250_do_shutdown(port); > } > > +/* > + * Wakes up the serial port if it has been runtime PM suspended. > + * > + * Note that we rely on the serial8250_rpm functions to manage the > + * runtime PM usage count. We also currently depend on the runtime > + * PM autosuspend timeout to keep the port awake until start_tx(). > + * Eventually we should just use runtime PM functions and not rely > + * on the autosuspend timeout. > + * > + * Caller must hold port->lock for port->runtime_suspended status. > + * Also the port drivers must hold port->lock when changing the > + * state for port->runtime_suspended in runtime PM functions. > + */ > +static int serial8250_wakeup(struct uart_port *port) > +{ > + struct uart_8250_port *up = up_to_u8250p(port); > + struct device *dev = up->port.dev; > + int err; > + > + if (!pm_runtime_enabled(dev)) > + return 0; > + > + if (!port->runtime_suspended) { > + pm_runtime_mark_last_busy(dev); > + return 0; > + } > + > + err = pm_request_resume(dev); > + if (err < 0) { > + dev_warn(dev, "wakeup failed: %d\n", err); > + return err; > + } > + > + return -EINPROGRESS; > +} Why can't this be done in core? > + > /* Nuvoton NPCM UARTs have a custom divisor calculation */ > static unsigned int npcm_get_divisor(struct uart_8250_port *up, > unsigned int baud) > @@ -3237,6 +3273,7 @@ static const struct uart_ops serial8250_pops = { > .break_ctl = serial8250_break_ctl, > .startup = serial8250_startup, > .shutdown = serial8250_shutdown, > + .wakeup = serial8250_wakeup, > .set_termios = serial8250_set_termios, > .set_ldisc = serial8250_set_ldisc, > .pm = serial8250_pm, Johan
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -1593,12 +1593,16 @@ static int omap8250_runtime_suspend(struct device *dev) { struct omap8250_priv *priv = dev_get_drvdata(dev); struct uart_8250_port *up; + struct uart_port *port; + unsigned long flags; /* In case runtime-pm tries this before we are setup */ if (!priv) return 0; up = serial8250_get_port(priv->line); + port = &up->port; + /* * When using 'no_console_suspend', the console UART must not be * suspended. Since driver suspend is managed by runtime suspend, @@ -1610,6 +1614,10 @@ static int omap8250_runtime_suspend(struct device *dev) return -EBUSY; } + spin_lock_irqsave(&port->lock, flags); + port->runtime_suspended = 1; + spin_unlock_irqrestore(&port->lock, flags); + if (priv->habit & UART_ERRATA_CLOCK_DISABLE) { int ret; @@ -1636,13 +1644,18 @@ static int omap8250_runtime_resume(struct device *dev) { struct omap8250_priv *priv = dev_get_drvdata(dev); struct uart_8250_port *up; + struct uart_port *port; + unsigned long flags; /* In case runtime-pm tries this before we are setup */ if (!priv) return 0; up = serial8250_get_port(priv->line); + port = &up->port; + /* Restore state with interrupts disabled */ + spin_lock_irqsave(&port->lock, flags); if (omap8250_lost_context(up)) omap8250_restore_regs(up); @@ -1651,6 +1664,12 @@ static int omap8250_runtime_resume(struct device *dev) priv->latency = priv->calc_latency; schedule_work(&priv->qos_work); + + port->runtime_suspended = 0; + spin_unlock_irqrestore(&port->lock, flags); + + uart_start_pending_tx(port); + return 0; } #endif diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -724,7 +724,7 @@ void serial8250_rpm_get_tx(struct uart_8250_port *p) rpm_active = xchg(&p->rpm_tx_active, 1); if (rpm_active) return; - pm_runtime_get_sync(p->port.dev); + pm_runtime_get(p->port.dev); } EXPORT_SYMBOL_GPL(serial8250_rpm_get_tx); @@ -2509,6 +2509,42 @@ static void serial8250_shutdown(struct uart_port *port) serial8250_do_shutdown(port); } +/* + * Wakes up the serial port if it has been runtime PM suspended. + * + * Note that we rely on the serial8250_rpm functions to manage the + * runtime PM usage count. We also currently depend on the runtime + * PM autosuspend timeout to keep the port awake until start_tx(). + * Eventually we should just use runtime PM functions and not rely + * on the autosuspend timeout. + * + * Caller must hold port->lock for port->runtime_suspended status. + * Also the port drivers must hold port->lock when changing the + * state for port->runtime_suspended in runtime PM functions. + */ +static int serial8250_wakeup(struct uart_port *port) +{ + struct uart_8250_port *up = up_to_u8250p(port); + struct device *dev = up->port.dev; + int err; + + if (!pm_runtime_enabled(dev)) + return 0; + + if (!port->runtime_suspended) { + pm_runtime_mark_last_busy(dev); + return 0; + } + + err = pm_request_resume(dev); + if (err < 0) { + dev_warn(dev, "wakeup failed: %d\n", err); + return err; + } + + return -EINPROGRESS; +} + /* Nuvoton NPCM UARTs have a custom divisor calculation */ static unsigned int npcm_get_divisor(struct uart_8250_port *up, unsigned int baud) @@ -3237,6 +3273,7 @@ static const struct uart_ops serial8250_pops = { .break_ctl = serial8250_break_ctl, .startup = serial8250_startup, .shutdown = serial8250_shutdown, + .wakeup = serial8250_wakeup, .set_termios = serial8250_set_termios, .set_ldisc = serial8250_set_ldisc, .pm = serial8250_pm,
We can use the wakeup() and uart_start_pending_tx() calls to wake up an idle serial port and send out the pending TX buffer on runtime PM resume. This allows us to remove the dependency to pm_runtime_irq_safe() for 8250_omap driver in the following patches. We manage the port runtime_suspended flag in the serial port driver as only the driver knows when the hardware is runtime PM suspended. Note that The current flag for rpm_tx_active cannot be used as it is TX specific for 8250_port. We already have serial8250_start_tx() call serial8250_rpm_get_tx(), and serial8250_stop_tx() call serial8250_rpm_put_tx() to take care of the runtime PM usage count for TX. To have the serial port driver call uart_start_pending_tx() on runtime resume, we must now use just pm_runtime_get() for serial8250_start_tx() instead of the sync version. With these changes we must now also flip the 8250_omap driver over to call uart_start_pending_tx(). That's currently the only user of UART_CAP_RPM. Signed-off-by: Tony Lindgren <tony@atomide.com> --- drivers/tty/serial/8250/8250_omap.c | 19 ++++++++++++++ drivers/tty/serial/8250/8250_port.c | 39 ++++++++++++++++++++++++++++- 2 files changed, 57 insertions(+), 1 deletion(-)