[PATCH 2/2] tty: serial core: use the ACPI PM state defines

[PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Linus Walleij]

From: Linus Walleij <linus.walleij@linaro.org>

The Documentation/serial/driver file defines that:

  State indicates the new state (defined by ACPI D0-D3),
  oldstate indicates the previous state.  Essentially, D0
  means fully on, D3 means powered down.

So let's change the code to actually using the defined ACPI
states instead of using magic numbers. Further it is clear
from the ACPI definitions that the state is a u8 so use this
data type.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/tty/serial/serial_core.c | 26 ++++++++++++++------------
 include/linux/serial_core.h      |  2 +-
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 2c7230a..f327115 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -34,6 +34,8 @@
 #include <linux/delay.h>
 #include <linux/mutex.h>
 
+#include <acpi/acstates.h> /* for power states */
+
 #include <asm/irq.h>
 #include <asm/uaccess.h>
 
@@ -59,7 +61,7 @@ static struct lock_class_key port_lock_key;
 static void uart_change_speed(struct tty_struct *tty, struct uart_state *state,
 					struct ktermios *old_termios);
 static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
-static void uart_change_pm(struct uart_state *state, int pm_state);
+static void uart_change_pm(struct uart_state *state, u8 pm_state);
 
 static void uart_port_shutdown(struct tty_port *port);
 
@@ -1365,7 +1367,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
 		spin_lock_irqsave(&port->lock, flags);
 	} else if (!uart_console(uport)) {
 		spin_unlock_irqrestore(&port->lock, flags);
-		uart_change_pm(state, 3);
+		uart_change_pm(state, ACPI_STATE_D3_HOT);
 		spin_lock_irqsave(&port->lock, flags);
 	}
 
@@ -1579,7 +1581,7 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
 	 * Make sure the device is in D0 state.
 	 */
 	if (port->count == 1)
-		uart_change_pm(state, 0);
+		uart_change_pm(state, ACPI_STATE_D0);
 
 	/*
 	 * Start up the serial port.
@@ -1620,7 +1622,7 @@ static void uart_line_info(struct seq_file *m, struct uart_driver *drv, int i)
 {
 	struct uart_state *state = drv->state + i;
 	struct tty_port *port = &state->port;
-	int pm_state;
+	u8 pm_state;
 	struct uart_port *uport = state->uart_port;
 	char stat_buf[32];
 	unsigned int status;
@@ -1646,7 +1648,7 @@ static void uart_line_info(struct seq_file *m, struct uart_driver *drv, int i)
 		mutex_lock(&port->mutex);
 		pm_state = state->pm_state;
 		if (pm_state)
-			uart_change_pm(state, 0);
+			uart_change_pm(state, ACPI_STATE_D0);
 		spin_lock_irq(&uport->lock);
 		status = uport->ops->get_mctrl(uport);
 		spin_unlock_irq(&uport->lock);
@@ -1897,7 +1899,7 @@ EXPORT_SYMBOL_GPL(uart_set_options);
  *
  * Locking: port->mutex has to be held
  */
-static void uart_change_pm(struct uart_state *state, int pm_state)
+static void uart_change_pm(struct uart_state *state, u8 pm_state)
 {
 	struct uart_port *port = state->uart_port;
 
@@ -1982,7 +1984,7 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
 		console_stop(uport->cons);
 
 	if (console_suspend_enabled || !uart_console(uport))
-		uart_change_pm(state, 3);
+		uart_change_pm(state, ACPI_STATE_D3_HOT);
 
 	mutex_unlock(&port->mutex);
 
@@ -2027,7 +2029,7 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 			termios = port->tty->termios;
 
 		if (console_suspend_enabled)
-			uart_change_pm(state, 0);
+			uart_change_pm(state, ACPI_STATE_D0);
 		uport->ops->set_termios(uport, &termios, NULL);
 		if (console_suspend_enabled)
 			console_start(uport->cons);
@@ -2037,7 +2039,7 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 		const struct uart_ops *ops = uport->ops;
 		int ret;
 
-		uart_change_pm(state, 0);
+		uart_change_pm(state, ACPI_STATE_D0);
 		spin_lock_irq(&uport->lock);
 		ops->set_mctrl(uport, 0);
 		spin_unlock_irq(&uport->lock);
@@ -2137,7 +2139,7 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 		uart_report_port(drv, port);
 
 		/* Power up port for set_mctrl() */
-		uart_change_pm(state, 0);
+		uart_change_pm(state, ACPI_STATE_D0);
 
 		/*
 		 * Ensure that the modem control lines are de-activated.
@@ -2161,7 +2163,7 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 		 * console if we have one.
 		 */
 		if (!uart_console(port))
-			uart_change_pm(state, 3);
+			uart_change_pm(state, ACPI_STATE_D3_HOT);
 	}
 }
 
@@ -2588,7 +2590,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 	}
 
 	state->uart_port = uport;
-	state->pm_state = -1;
+	state->pm_state = ACPI_STATE_UNKNOWN;
 
 	uport->cons = drv->cons;
 	uport->state = state;
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index c6690a2..43e8d87 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -214,7 +214,7 @@ static inline void serial_port_out(struct uart_port *up, int offset, int value)
 struct uart_state {
 	struct tty_port		port;
 
-	int			pm_state;
+	u8			pm_state;
 	struct circ_buf		xmit;
 
 	struct uart_port	*uart_port;
-- 
1.7.11.3

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Alan Cox]

On Thu, 6 Dec 2012 19:46:52 +0100
Linus Walleij <linus.walleij@stericsson.com> wrote:

> From: Linus Walleij <linus.walleij@linaro.org>
> 
> The Documentation/serial/driver file defines that:
> 
>   State indicates the new state (defined by ACPI D0-D3),
>   oldstate indicates the previous state.  Essentially, D0
>   means fully on, D3 means powered down.
> 
> So let's change the code to actually using the defined ACPI
> states instead of using magic numbers.

The "magic numbers" being "1" to mean one, "2" to mean two etc..

Almost none of the platforms using the serial driver even have ACPI so
this seems to be an obfuscation of a simple numbering system for a
subsystem specific set of definitions that may or may not fit in future.

What are you going to do if it turns out serial ports on some platform
have a state that doesn't fit ACPI_STATE_foo because its got a
behaviour that isn't in the ACPI specification ?

This seems to be tying stuff together in a way that will just cause
future pain.

Alan

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Linus Walleij]

On Thu, Dec 6, 2012 at 8:31 PM, Alan Cox <alan@linux.intel.com> wrote:

> Almost none of the platforms using the serial driver even have ACPI so
> this seems to be an obfuscation of a simple numbering system for a
> subsystem specific set of definitions that may or may not fit in future.

OK so we need to get away from using the ACPI numbering scheme.
What about we define something in the <linux/tty.h> file instead
and delete the paragraph from the documentation saying it is related
to ACPI? (Will try this next.)

Yours,
Linus Walleij

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Alan Cox]

On Thu, 6 Dec 2012 20:31:15 +0100
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Thu, Dec 6, 2012 at 8:31 PM, Alan Cox <alan@linux.intel.com> wrote:
> 
> > Almost none of the platforms using the serial driver even have ACPI so
> > this seems to be an obfuscation of a simple numbering system for a
> > subsystem specific set of definitions that may or may not fit in future.
> 
> OK so we need to get away from using the ACPI numbering scheme.

So whats wrong with 0 1 2 3 ?

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Linus Walleij]

On Thu, Dec 6, 2012 at 8:40 PM, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> On Thu, 6 Dec 2012 20:31:15 +0100
> Linus Walleij <linus.walleij@linaro.org> wrote:
>
>> On Thu, Dec 6, 2012 at 8:31 PM, Alan Cox <alan@linux.intel.com> wrote:
>>
>> > Almost none of the platforms using the serial driver even have ACPI so
>> > this seems to be an obfuscation of a simple numbering system for a
>> > subsystem specific set of definitions that may or may not fit in future.
>>
>> OK so we need to get away from using the ACPI numbering scheme.
>
> So whats wrong with 0 1 2 3 ?

Mainly what is wrong is the documentation that says that this correlates
to the ACPI D-states.

But we're working to get a serial driver power aware and need to
start to let device drivers go to different power states, and then
we need to let the core handle not only state 0 and 3 (as it is
using today) but also 1 and 2 (currently not used in the serial
core). And if several device drivers shall do that it could be a
good idea to have some idea of what the numbers actually
mean, roughly atleast.

Yours,
Linus Walleij

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Rafael J. Wysocki]

On Thursday, December 06, 2012 08:31:15 PM Linus Walleij wrote:
> On Thu, Dec 6, 2012 at 8:31 PM, Alan Cox <alan@linux.intel.com> wrote:
> 
> > Almost none of the platforms using the serial driver even have ACPI so
> > this seems to be an obfuscation of a simple numbering system for a
> > subsystem specific set of definitions that may or may not fit in future.
> 
> OK so we need to get away from using the ACPI numbering scheme.
> What about we define something in the <linux/tty.h> file instead
> and delete the paragraph from the documentation saying it is related
> to ACPI? (Will try this next.)

Deleting that paragraph would be fine by me, FWIW.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Alan Cox]

On Thu, 6 Dec 2012 20:31:15 +0100
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Thu, Dec 6, 2012 at 8:31 PM, Alan Cox <alan@linux.intel.com> wrote:
> 
> > Almost none of the platforms using the serial driver even have ACPI
> > so this seems to be an obfuscation of a simple numbering system for
> > a subsystem specific set of definitions that may or may not fit in
> > future.
> 
> OK so we need to get away from using the ACPI numbering scheme.
> What about we define something in the <linux/tty.h> file instead
> and delete the paragraph from the documentation saying it is related
> to ACPI? (Will try this next.)

What about just using 0, 1, 2, 3 to indicate states similar to D0-D3
which as a base concept everyone is familiar with ?

If we need something more than that, then can we talk about what the
actual extra non 0/3 states needed are and how to get a generic
meaningful definition, or indeed whether a number rather than flag bits
makes sense ?

Start with the driver/platform that causes the concern and then the
rest is probably blindingly obvious.

Alan

Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

[Linus Walleij]

On Fri, Dec 7, 2012 at 12:36 AM, Alan Cox <alan@linux.intel.com> wrote:

> What about just using 0, 1, 2, 3 to indicate states similar to D0-D3
> which as a base concept everyone is familiar with ?

Sorry, I might be something of an oddity, but ACPI is not used on
ARM systems as of today, and I was completely confused by
these:

  uart_change_pm(state, 0);
  uart_change_pm(state, 3);

I was just like ... eh ... 0? 3?

No ACPI associations existed in my head until I finally found
the note in the documentation saying that it corresponds to
ACPI states.

We are a few kernel developers these days who never ever
worked on Intel, sorry for this, but that's what we are like :-)

> If we need something more than that, then can we talk about what the
> actual extra non 0/3 states needed are and how to get a generic
> meaningful definition, or indeed whether a number rather than flag bits
> makes sense ?

Sure, I think my colleague Rickard will soon post another
patch for controlling the state 1,2 bottom-up from drivers.

> Start with the driver/platform that causes the concern and then the
> rest is probably blindingly obvious.

It's the introduction of runtime power management for the ARM
amba-pl011.c UART driver that confuse us.

It is atleast obvious that none of the 5 ARM platforms using that
driver do not use ACPI, and I expect the situation to be the same
for most of the ARM drivers.

Yours,
Linus Walleij