[PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

With dt boot, uart wakeup after suspend is non functional while using
"no_console_suspend" in the bootargs. With "no_console_suspend" used, we
should prevent the runtime suspend of the uart port which is getting used
as an console.

Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
Cc: Felipe Balbi<balbi@ti.com>
Cc: Rajendra nayak<rnayak@ti.com>
Tested on omap5430evm, omap4430sdp.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
---
v2->v3
Based on Kevin Hilman and Santosh Shilimkar comments, modified
serial core/driver layer to bypass runtime suspend 
for console uart while using "no_console_suspend".

This patch is based on Santosh Shilimkar serial patch[1]

[1]: http://permalink.gmane.org/gmane.linux.ports.arm.omap/95828
	
 drivers/tty/serial/omap-serial.c |    5 ++++-
 drivers/tty/serial/serial_core.c |    3 +++
 include/linux/serial_core.h      |    1 +
 3 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 08332f3..81a1760 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1582,7 +1582,7 @@ static int serial_omap_runtime_suspend(struct device *dev)
 	struct uart_omap_port *up = dev_get_drvdata(dev);
 	struct omap_uart_port_info *pdata = dev->platform_data;
 
-	if (!up)
+	if (!up || (!console_suspend_enabled && up->port.port_is_console))
 		return -EINVAL;
 
 	if (!pdata)
@@ -1614,6 +1614,9 @@ static int serial_omap_runtime_resume(struct device *dev)
 
 	int loss_cnt = serial_omap_get_context_loss_count(up);
 
+	if (!console_suspend_enabled && up->port.port_is_console)
+		return -EINVAL;
+
 	if (loss_cnt < 0) {
 		dev_err(dev, "serial_omap_get_context_loss_count failed : %d\n",
 			loss_cnt);
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index a400002..6c8b041 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2594,6 +2594,9 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 	uport->cons = drv->cons;
 	uport->state = state;
 
+	if (uart_console(uport))
+		uport->port_is_console = true;
+
 	/*
 	 * If this port is a console, then the spinlock is already
 	 * initialised.
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 87d4bbc..c944414 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -194,6 +194,7 @@ struct uart_port {
 	unsigned char		irq_wake;
 	unsigned char		unused[2];
 	void			*private_data;		/* generic platform data pointer */
+	bool			port_is_console;
 };
 
 static inline int serial_port_in(struct uart_port *up, int offset)
-- 
1.7.1

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Kevin Hilman]

Sourav Poddar <sourav.poddar@ti.com> writes:

> With dt boot, uart wakeup after suspend is non functional while using
> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
> should prevent the runtime suspend of the uart port which is getting used
> as an console.
>
> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
> Cc: Felipe Balbi<balbi@ti.com>
> Cc: Rajendra nayak<rnayak@ti.com>
> Tested on omap5430evm, omap4430sdp.
>
> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>

Rather than make these special checks inside the driver's runtime PM
callbacks, you should just disable runtime PM (pm_runtime_disable())

Then, this should be broken into 2 patches.

1) serial core: add the '->is_console' flag.  (nit on naming: don't call
   it port_is_console, since the struct is already a uart_port)

2) In the OMAP UART driver's ->prepare callback, check the is_console flag
   and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
   the drivers's ->complete callback.

Kevin

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Russell King - ARM Linux]

On Fri, Apr 05, 2013 at 06:45:33PM +0530, Sourav Poddar wrote:
> With dt boot, uart wakeup after suspend is non functional while using
> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
> should prevent the runtime suspend of the uart port which is getting used
> as an console.
> 
> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
> Cc: Felipe Balbi<balbi@ti.com>
> Cc: Rajendra nayak<rnayak@ti.com>
> Tested on omap5430evm, omap4430sdp.
> 
> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
> ---
> v2->v3
> Based on Kevin Hilman and Santosh Shilimkar comments, modified
> serial core/driver layer to bypass runtime suspend 
> for console uart while using "no_console_suspend".
> 
> This patch is based on Santosh Shilimkar serial patch[1]

Rather than introducing this "port_is_console" thing, please move
uart_console() into the serial_core.h header file, making it an inline
function, and use that in omap-serial.c.

Remember to fix drivers/tty/serial/mpc52xx_uart.c as well for that change.

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

Hi Kevin,
On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
> Sourav Poddar<sourav.poddar@ti.com>  writes:
>
>> With dt boot, uart wakeup after suspend is non functional while using
>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
>> should prevent the runtime suspend of the uart port which is getting used
>> as an console.
>>
>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
>> Cc: Felipe Balbi<balbi@ti.com>
>> Cc: Rajendra nayak<rnayak@ti.com>
>> Tested on omap5430evm, omap4430sdp.
>>
>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
> Rather than make these special checks inside the driver's runtime PM
> callbacks, you should just disable runtime PM (pm_runtime_disable())
>
> Then, this should be broken into 2 patches.
>
> 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
>     it port_is_console, since the struct is already a uart_port)
>
> 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
>     and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
>     the drivers's ->complete callback.
>
> Kevin

I was working on your above suggestions, but realised there is not only 
console
uart which has the requirement of keeping the clocks enabled while going on
suspend.

If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
"no_idle_on_suspend" property used.

     ocmcram: ocmcram@40300000 {
                         compatible = "ti,am3352-ocmcram";
                         reg = <0x40300000 0x10000>;
                         ti,hwmods = "ocmcram";
                         ti,no_idle_on_suspend;
         };
This property gets checked in omap_device file and correspondingly 
od->flags is set.

Based on your above inputs, the patches which I cooked up is inlined[1]. 
Though, the below
patches works fine for uart case. The patches will effect ocmcram case 
and I am inling them
"just for discussion".

I am not sure, if there is any other cleaner way of getting around this 
"no_idle_on_suspend" flag
as they are getting used for ocmcram also. ?

Thanks,
Sourav

[1]:
From: Sourav Poddar <sourav.poddar@ti.com>
Date: Wed, 13 Mar 2013 20:32:36 +0530
Subject: [PATCH 1/2] arm: mach-omap2: remove 
"OMAP_DEVICE_NO_IDLE_ON_SUSPEND" check

Remove the "OMAP_DEVICE_NO_IDLE_ON_SUSPEND" check, since serial core and 
driver
takes care of the case when "no_console_suspend" is used in the bootargs and
you need to keep the clock enable for console even while suspend.

Tested on omap5430evm, omap4430sdp.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
---
  arch/arm/mach-omap2/omap_device.c |    7 +------
  1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mach-omap2/omap_device.c 
b/arch/arm/mach-omap2/omap_device.c
index 381be7a..d6dce8f 100644
--- a/arch/arm/mach-omap2/omap_device.c
+++ b/arch/arm/mach-omap2/omap_device.c
@@ -620,11 +620,8 @@ static int _od_suspend_noirq(struct device *dev)
         ret = pm_generic_suspend_noirq(dev);

         if (!ret && !pm_runtime_status_suspended(dev)) {
-               if (pm_generic_runtime_suspend(dev) == 0) {
-                       if (!(od->flags & OMAP_DEVICE_NO_IDLE_ON_SUSPEND))
-                               omap_device_idle(pdev);
+               if (pm_generic_runtime_suspend(dev) == 0)
                         od->flags |= OMAP_DEVICE_SUSPENDED;
-               }
         }

         return ret;
@@ -638,8 +635,6 @@ static int _od_resume_noirq(struct device *dev)
         if ((od->flags & OMAP_DEVICE_SUSPENDED) &&
             !pm_runtime_status_suspended(dev)) {
                 od->flags &= ~OMAP_DEVICE_SUSPENDED;
-               if (!(od->flags & OMAP_DEVICE_NO_IDLE_ON_SUSPEND))
-                       omap_device_enable(pdev);
                 pm_generic_runtime_resume(dev);
         }

--

From: Sourav Poddar <sourav.poddar@ti.com>
Date: Wed, 13 Mar 2013 20:32:36 +0530
Subject: [PATCH 2/2] driver: serial: omap: add prepare/complete callback 
for "no_console_suspend" case

This patch adapt the serial core/driver to take care of the case when 
"no_console_suspend"
is used in the bootargs. This patch will remove dependency to set 
od->flags to
"OMAP_DEVICE_NO_IDLE_ON_SUSPEND" in serial.c(non dt case) and 
omap_device.c(dt case).

Prepare and complete callbacks will ensure that clocks remain active for 
the console
uart when "no_console_suspend" is used in the bootargs.

Tested on omap5430evm, omap4430sdp.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
---
  drivers/tty/serial/omap-serial.c |   20 ++++++++++++++++++++
  drivers/tty/serial/serial_core.c |    3 +++
  include/linux/serial_core.h      |    1 +
  3 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c 
b/drivers/tty/serial/omap-serial.c
index 08332f3..b726b2b 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1278,6 +1278,24 @@ static struct uart_driver serial_omap_reg = {
  };

  #ifdef CONFIG_PM_SLEEP
+static int serial_omap_prepare(struct device *dev)
+{
+       struct uart_omap_port *up = dev_get_drvdata(dev);
+
+       if (!console_suspend_enabled && up->port.is_console)
+               pm_runtime_disable(dev);
+
+       return 0;
+}
+
+static void serial_omap_complete(struct device *dev)
+{
+       struct uart_omap_port *up = dev_get_drvdata(dev);
+
+       if (!console_suspend_enabled && up->port.is_console)
+               pm_runtime_enable(dev);
+}
+
  static int serial_omap_suspend(struct device *dev)
  {
         struct uart_omap_port *up = dev_get_drvdata(dev);
@@ -1632,6 +1650,8 @@ static const struct dev_pm_ops 
serial_omap_dev_pm_ops = {
         SET_SYSTEM_SLEEP_PM_OPS(serial_omap_suspend, serial_omap_resume)
         SET_RUNTIME_PM_OPS(serial_omap_runtime_suspend,
                                 serial_omap_runtime_resume, NULL)
+       .prepare        = serial_omap_prepare,
+       .complete       = serial_omap_complete,
  };

  #if defined(CONFIG_OF)
diff --git a/drivers/tty/serial/serial_core.c 
b/drivers/tty/serial/serial_core.c
index a400002..c4d9328 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2594,6 +2594,9 @@ int uart_add_one_port(struct uart_driver *drv, 
struct uart_port *uport)
         uport->cons = drv->cons;
         uport->state = state;

+       if (uart_console(uport))
+               uport->is_console = true;
+
         /*
          * If this port is a console, then the spinlock is already
          * initialised.
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 87d4bbc..7fcdd90 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -194,6 +194,7 @@ struct uart_port {
         unsigned char           irq_wake;
         unsigned char           unused[2];
         void                    *private_data;          /* generic 
platform data pointer */
+       bool                    is_console;
  };

  static inline int serial_port_in(struct uart_port *up, int offset)

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Kevin Hilman]

Sourav Poddar <sourav.poddar@ti.com> writes:

> Hi Kevin,
> On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
>> Sourav Poddar<sourav.poddar@ti.com>  writes:
>>
>>> With dt boot, uart wakeup after suspend is non functional while using
>>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
>>> should prevent the runtime suspend of the uart port which is getting used
>>> as an console.
>>>
>>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
>>> Cc: Felipe Balbi<balbi@ti.com>
>>> Cc: Rajendra nayak<rnayak@ti.com>
>>> Tested on omap5430evm, omap4430sdp.
>>>
>>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
>> Rather than make these special checks inside the driver's runtime PM
>> callbacks, you should just disable runtime PM (pm_runtime_disable())
>>
>> Then, this should be broken into 2 patches.
>>
>> 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
>>     it port_is_console, since the struct is already a uart_port)
>>
>> 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
>>     and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
>>     the drivers's ->complete callback.
>>
>> Kevin
>
> I was working on your above suggestions, but realised there is not
> only console
> uart which has the requirement of keeping the clocks enabled while going on
> suspend.
>
> If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
> "no_idle_on_suspend" property used.

Can you please ask the AM33xx folks how (and why) this is being used?

I don't see/find a driver for this device in mainline, so without a
driver this flag will not be used.

>     ocmcram: ocmcram@40300000 {
>                         compatible = "ti,am3352-ocmcram";
>                         reg = <0x40300000 0x10000>;
>                         ti,hwmods = "ocmcram";
>                         ti,no_idle_on_suspend;
>         };
> This property gets checked in omap_device file and correspondingly
> od->flags is set.
>
> Based on your above inputs, the patches which I cooked up is
> inlined[1]. Though, the below
> patches works fine for uart case. The patches will effect ocmcram case
> and I am inling them
> "just for discussion".

Could you also have a look at Russell's suggestion for getting rid of
the 'is_console' flag.

Thanks,

Kevin

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

Hi Russell,
On Monday 08 April 2013 10:44 PM, Russell King - ARM Linux wrote:
> On Fri, Apr 05, 2013 at 06:45:33PM +0530, Sourav Poddar wrote:
>> With dt boot, uart wakeup after suspend is non functional while using
>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
>> should prevent the runtime suspend of the uart port which is getting used
>> as an console.
>>
>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
>> Cc: Felipe Balbi<balbi@ti.com>
>> Cc: Rajendra nayak<rnayak@ti.com>
>> Tested on omap5430evm, omap4430sdp.
>>
>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
>> ---
>> v2->v3
>> Based on Kevin Hilman and Santosh Shilimkar comments, modified
>> serial core/driver layer to bypass runtime suspend
>> for console uart while using "no_console_suspend".
>>
>> This patch is based on Santosh Shilimkar serial patch[1]
> Rather than introducing this "port_is_console" thing, please move
> uart_console() into the serial_core.h header file, making it an inline
> function, and use that in omap-serial.c.
>
> Remember to fix drivers/tty/serial/mpc52xx_uart.c as well for that change.
Thanks for the pointer. Will take care of your suggestions
in the next version.

~Sourav

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

Hi,
On Wednesday 10 April 2013 12:37 AM, Kevin Hilman wrote:
> Sourav Poddar<sourav.poddar@ti.com>  writes:
>
>> Hi Kevin,
>> On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
>>> Sourav Poddar<sourav.poddar@ti.com>   writes:
>>>
>>>> With dt boot, uart wakeup after suspend is non functional while using
>>>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
>>>> should prevent the runtime suspend of the uart port which is getting used
>>>> as an console.
>>>>
>>>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
>>>> Cc: Felipe Balbi<balbi@ti.com>
>>>> Cc: Rajendra nayak<rnayak@ti.com>
>>>> Tested on omap5430evm, omap4430sdp.
>>>>
>>>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
>>> Rather than make these special checks inside the driver's runtime PM
>>> callbacks, you should just disable runtime PM (pm_runtime_disable())
>>>
>>> Then, this should be broken into 2 patches.
>>>
>>> 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
>>>      it port_is_console, since the struct is already a uart_port)
>>>
>>> 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
>>>      and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
>>>      the drivers's ->complete callback.
>>>
>>> Kevin
>> I was working on your above suggestions, but realised there is not
>> only console
>> uart which has the requirement of keeping the clocks enabled while going on
>> suspend.
>>
>> If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
>> "no_idle_on_suspend" property used.
> Can you please ask the AM33xx folks how (and why) this is being used?
>
> I don't see/find a driver for this device in mainline, so without a
> driver this flag will not be used.
>
Looping in Vaibhav Bedia for ocmcram..

[Vaibhav]:
   There is a discussion going on about a cleaner way of handling
   ti, no_idle_on_suspend" part (as this is a sort of hack). We got a way
   around for UART ($subject) by making serial core/driver handle this 
for us.
   But with this, we will delete codes around "no_idle_on_suspend" flag in
   omap_device file.

   But, we realised that its not only UART which requires the clocks to 
be active
   whie going for suspend. There is a dts entry for ocmcram also.

   As Kevin also pointed out, we don't see a driver for this device in 
mainline, It would be
   great if you can explain how its getting used?

   You can find the complete discussion on v3 here:
      https://lkml.org/lkml/2013/4/5/239

>>      ocmcram: ocmcram@40300000 {
>>                          compatible = "ti,am3352-ocmcram";
>>                          reg =<0x40300000 0x10000>;
>>                          ti,hwmods = "ocmcram";
>>                          ti,no_idle_on_suspend;
>>          };
>> This property gets checked in omap_device file and correspondingly
>> od->flags is set.
>>
>> Based on your above inputs, the patches which I cooked up is
>> inlined[1]. Though, the below
>> patches works fine for uart case. The patches will effect ocmcram case
>> and I am inling them
>> "just for discussion".
> Could you also have a look at Russell's suggestion for getting rid of
> the 'is_console' flag.
>
[Kevin]: Yes, will do that.
> Thanks,
>
> Kevin
~Sourav

RE: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Bedia, Vaibhav]

Hi Sourav, Kevin,

On Wed, Apr 10, 2013 at 11:37:28, Poddar, Sourav wrote:
> Hi,
> On Wednesday 10 April 2013 12:37 AM, Kevin Hilman wrote:
> > Sourav Poddar<sourav.poddar@ti.com>  writes:
> >
> >> Hi Kevin,
> >> On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
> >>> Sourav Poddar<sourav.poddar@ti.com>   writes:
> >>>
> >>>> With dt boot, uart wakeup after suspend is non functional while using
> >>>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
> >>>> should prevent the runtime suspend of the uart port which is getting used
> >>>> as an console.
> >>>>
> >>>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
> >>>> Cc: Felipe Balbi<balbi@ti.com>
> >>>> Cc: Rajendra nayak<rnayak@ti.com>
> >>>> Tested on omap5430evm, omap4430sdp.
> >>>>
> >>>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
> >>> Rather than make these special checks inside the driver's runtime PM
> >>> callbacks, you should just disable runtime PM (pm_runtime_disable())
> >>>
> >>> Then, this should be broken into 2 patches.
> >>>
> >>> 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
> >>>      it port_is_console, since the struct is already a uart_port)
> >>>
> >>> 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
> >>>      and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
> >>>      the drivers's ->complete callback.
> >>>
> >>> Kevin
> >> I was working on your above suggestions, but realised there is not
> >> only console
> >> uart which has the requirement of keeping the clocks enabled while going on
> >> suspend.
> >>
> >> If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
> >> "no_idle_on_suspend" property used.
> > Can you please ask the AM33xx folks how (and why) this is being used?
> >
> > I don't see/find a driver for this device in mainline, so without a
> > driver this flag will not be used.
> >
> Looping in Vaibhav Bedia for ocmcram..
> 
> [Vaibhav]:
>    There is a discussion going on about a cleaner way of handling
>    ti, no_idle_on_suspend" part (as this is a sort of hack). We got a way
>    around for UART ($subject) by making serial core/driver handle this 
> for us.
>    But with this, we will delete codes around "no_idle_on_suspend" flag in
>    omap_device file.
> 
>    But, we realised that its not only UART which requires the clocks to 
> be active
>    whie going for suspend. There is a dts entry for ocmcram also.
> 
>    As Kevin also pointed out, we don't see a driver for this device in 
> mainline, It would be
>    great if you can explain how its getting used?
> 
>    You can find the complete discussion on v3 here:
>       https://lkml.org/lkml/2013/4/5/239
> 

The flag in question is used to ensure that the clock to OCMC RAM is not
disabled by the PM code.

>From the changelog which added this flag:

"Note: OCMC RAM is part of the PER power domain and supports
 retention. The assembly code for low power entry/exit will
 run from OCMC RAM. To ensure that the OMAP PM code does not
 attempt to disable the clock to OCMC RAM as part of the
 suspend process add the no_idle_on_suspend flag."

We had discussed about the usage of this flag in the RFC version
of the patch [1].

Regards,
Vaibhav

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2012-November/129510.html

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

Hi Vaibhav,
On Wednesday 10 April 2013 11:49 AM, Bedia, Vaibhav wrote:
> Hi Sourav, Kevin,
>
> On Wed, Apr 10, 2013 at 11:37:28, Poddar, Sourav wrote:
>> Hi,
>> On Wednesday 10 April 2013 12:37 AM, Kevin Hilman wrote:
>>> Sourav Poddar<sourav.poddar@ti.com>   writes:
>>>
>>>> Hi Kevin,
>>>> On Friday 05 April 2013 11:10 PM, Kevin Hilman wrote:
>>>>> Sourav Poddar<sourav.poddar@ti.com>    writes:
>>>>>
>>>>>> With dt boot, uart wakeup after suspend is non functional while using
>>>>>> "no_console_suspend" in the bootargs. With "no_console_suspend" used, we
>>>>>> should prevent the runtime suspend of the uart port which is getting used
>>>>>> as an console.
>>>>>>
>>>>>> Cc: Santosh Shilimkar<santosh.shilimkar@ti.com>
>>>>>> Cc: Felipe Balbi<balbi@ti.com>
>>>>>> Cc: Rajendra nayak<rnayak@ti.com>
>>>>>> Tested on omap5430evm, omap4430sdp.
>>>>>>
>>>>>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
>>>>> Rather than make these special checks inside the driver's runtime PM
>>>>> callbacks, you should just disable runtime PM (pm_runtime_disable())
>>>>>
>>>>> Then, this should be broken into 2 patches.
>>>>>
>>>>> 1) serial core: add the '->is_console' flag.  (nit on naming: don't call
>>>>>       it port_is_console, since the struct is already a uart_port)
>>>>>
>>>>> 2) In the OMAP UART driver's ->prepare callback, check the is_console flag
>>>>>       and pm_runtime_disable() accordingly  (then pm_runtime_enable() in
>>>>>       the drivers's ->complete callback.
>>>>>
>>>>> Kevin
>>>> I was working on your above suggestions, but realised there is not
>>>> only console
>>>> uart which has the requirement of keeping the clocks enabled while going on
>>>> suspend.
>>>>
>>>> If you see arch/arm/boot/dts/am33xx.dtsi, there is a ocmcram which has
>>>> "no_idle_on_suspend" property used.
>>> Can you please ask the AM33xx folks how (and why) this is being used?
>>>
>>> I don't see/find a driver for this device in mainline, so without a
>>> driver this flag will not be used.
>>>
>> Looping in Vaibhav Bedia for ocmcram..
>>
>> [Vaibhav]:
>>     There is a discussion going on about a cleaner way of handling
>>     ti, no_idle_on_suspend" part (as this is a sort of hack). We got a way
>>     around for UART ($subject) by making serial core/driver handle this
>> for us.
>>     But with this, we will delete codes around "no_idle_on_suspend" flag in
>>     omap_device file.
>>
>>     But, we realised that its not only UART which requires the clocks to
>> be active
>>     whie going for suspend. There is a dts entry for ocmcram also.
>>
>>     As Kevin also pointed out, we don't see a driver for this device in
>> mainline, It would be
>>     great if you can explain how its getting used?
>>
>>     You can find the complete discussion on v3 here:
>>        https://lkml.org/lkml/2013/4/5/239
>>
> The flag in question is used to ensure that the clock to OCMC RAM is not
> disabled by the PM code.
>
>  From the changelog which added this flag:
>
> "Note: OCMC RAM is part of the PER power domain and supports
>   retention. The assembly code for low power entry/exit will
>   run from OCMC RAM. To ensure that the OMAP PM code does not
>   attempt to disable the clock to OCMC RAM as part of the
>   suspend process add the no_idle_on_suspend flag."
>
> We had discussed about the usage of this flag in the RFC version
> of the patch [1].
>
Yes, had a look at that and found your situation similar to UART.

But how exactly this gets used, I mean I don't  see any drivers/ in mainline
making use of this compatible string  "ti,am3352-ocmcram".  ?
> Regards,
> Vaibhav
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2012-November/129510.html

RE: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Bedia, Vaibhav]

Hi Sourav,

On Wed, Apr 10, 2013 at 15:13:44, Poddar, Sourav wrote:
[...]
> Yes, had a look at that and found your situation similar to UART.
> 
> But how exactly this gets used, I mean I don't  see any drivers/ in mainline
> making use of this compatible string  "ti,am3352-ocmcram".  ?

OCMC clock is enabled during bootup (not sure whether that's the h/w
default or ROM does it) since the initial bootloader runs from there.
By marking the corresponding hwmod with HWMOD_INIT_NO_IDLE we leave the
clock running. Right now the sram code under arch/arm/plat-omap/ is what
manages the OCMC. I guess this needs to move somewhere under drivers/
and start managing the clocks. Even then we'll need a mechanism
to leave the clocks running as part of the kernel suspend process
since the assembly code which runs at the fag end of the suspend
process runs out of OCMC and hence we can't cut its clock.

On AM335x, the OCMC clock is cut to have PER power domain transition
but that's done in the WKUP-M3 firmware when going down. During the
wakeup sequence, WKUP-M3 re-enables the OCMC clock so that when the
kernel resumes the h/w state is same.

Regards,
Vaibhav

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Kevin Hilman]

"Bedia, Vaibhav" <vaibhav.bedia@ti.com> writes:

> Hi Sourav,
>
> On Wed, Apr 10, 2013 at 15:13:44, Poddar, Sourav wrote:
> [...]
>> Yes, had a look at that and found your situation similar to UART.
>> 
>> But how exactly this gets used, I mean I don't  see any drivers/ in mainline
>> making use of this compatible string  "ti,am3352-ocmcram".  ?
>
> OCMC clock is enabled during bootup (not sure whether that's the h/w
> default or ROM does it) since the initial bootloader runs from there.
> By marking the corresponding hwmod with HWMOD_INIT_NO_IDLE we leave the
> clock running. Right now the sram code under arch/arm/plat-omap/ is what
> manages the OCMC. I guess this needs to move somewhere under drivers/
> and start managing the clocks. Even then we'll need a mechanism
> to leave the clocks running as part of the kernel suspend process
> since the assembly code which runs at the fag end of the suspend
> process runs out of OCMC and hence we can't cut its clock.
>
> On AM335x, the OCMC clock is cut to have PER power domain transition
> but that's done in the WKUP-M3 firmware when going down. During the
> wakeup sequence, WKUP-M3 re-enables the OCMC clock so that when the
> kernel resumes the h/w state is same.

OK, but *today*, in *mainline*, where in the linux kernel (not the M3
firmware) is the OCMRAM clock cut during suspend?

>From what I can see, there is no driver for this device, so there are no
system PM calls being done for that device, and thus no omap_device
calls being done for that device, so the no_idle_on_suspend has no
effect.

Kevin

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Kevin Hilman]

Kevin Hilman <khilman@linaro.org> writes:

> "Bedia, Vaibhav" <vaibhav.bedia@ti.com> writes:
>
>> Hi Sourav,
>>
>> On Wed, Apr 10, 2013 at 15:13:44, Poddar, Sourav wrote:
>> [...]
>>> Yes, had a look at that and found your situation similar to UART.
>>> 
>>> But how exactly this gets used, I mean I don't  see any drivers/ in mainline
>>> making use of this compatible string  "ti,am3352-ocmcram".  ?
>>
>> OCMC clock is enabled during bootup (not sure whether that's the h/w
>> default or ROM does it) since the initial bootloader runs from there.
>> By marking the corresponding hwmod with HWMOD_INIT_NO_IDLE we leave the
>> clock running. Right now the sram code under arch/arm/plat-omap/ is what
>> manages the OCMC. I guess this needs to move somewhere under drivers/
>> and start managing the clocks. Even then we'll need a mechanism
>> to leave the clocks running as part of the kernel suspend process
>> since the assembly code which runs at the fag end of the suspend
>> process runs out of OCMC and hence we can't cut its clock.
>>
>> On AM335x, the OCMC clock is cut to have PER power domain transition
>> but that's done in the WKUP-M3 firmware when going down. During the
>> wakeup sequence, WKUP-M3 re-enables the OCMC clock so that when the
>> kernel resumes the h/w state is same.
>
> OK, but *today*, in *mainline*, where in the linux kernel (not the M3
> firmware) is the OCMRAM clock cut during suspend?
>
> From what I can see, there is no driver for this device, so there are no
> system PM calls being done for that device, and thus no omap_device
> calls being done for that device, so the no_idle_on_suspend has no
> effect.

OK, I think I confused things here, sorry. I was thinking runtime PM
here, but wrote system PM.  The no_idle_on_suspend feature only affects
system PM, and the omap_device calls will still be called during system
PM, even without a driver.

That being said, the commit below[1], added in v3.6 should prevent the
any automaic clock gating for devices without drivers bound.  Since
there is no driver for the OCM RAM block, you shouldn't be affected by
the automatic idle on suspend anyways.

So, my proposal is that Sourav remove that flag from the AM33xx hwmod
when he removes this feature.

Kevin


[1]
commit 72bb6f9b51c82c820ddef892455a85b115460904
Author: Kevin Hilman <khilman@ti.com>
Date:   Tue Jul 10 15:29:04 2012 -0700

    ARM: OMAP: omap_device: don't attempt late suspend if no driver bound
    
    Currently, the omap_device PM domain layer uses the late suspend and
    early resume callbacks to ensure devices are in their low power
    states.
    
    However, this is attempted even in cases where a driver probe has
    failed.  If a driver's ->probe() method fails, the driver is likely in
    a state where it is not expecting its runtime PM callbacks to be
    called, yet currently the omap_device PM domain code attempts to call
    the drivers callbacks.
    
    To fix, use the omap_device driver_status field to check whether a
    driver is bound to the omap_device before attempting to trigger driver
    callbacks.
    
    Reviewed-by: Paul Walmsley <paul@pwsan.com>
    Signed-off-by: Kevin Hilman <khilman@ti.com>

RE: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Bedia, Vaibhav]

Hi Kevin,

On Thu, Apr 11, 2013 at 19:45:33, Kevin Hilman wrote:
> Kevin Hilman <khilman@linaro.org> writes:
> 
> > "Bedia, Vaibhav" <vaibhav.bedia@ti.com> writes:
> >
> >> Hi Sourav,
> >>
> >> On Wed, Apr 10, 2013 at 15:13:44, Poddar, Sourav wrote:
> >> [...]
> >>> Yes, had a look at that and found your situation similar to UART.
> >>> 
> >>> But how exactly this gets used, I mean I don't  see any drivers/ in mainline
> >>> making use of this compatible string  "ti,am3352-ocmcram".  ?
> >>
> >> OCMC clock is enabled during bootup (not sure whether that's the h/w
> >> default or ROM does it) since the initial bootloader runs from there.
> >> By marking the corresponding hwmod with HWMOD_INIT_NO_IDLE we leave the
> >> clock running. Right now the sram code under arch/arm/plat-omap/ is what
> >> manages the OCMC. I guess this needs to move somewhere under drivers/
> >> and start managing the clocks. Even then we'll need a mechanism
> >> to leave the clocks running as part of the kernel suspend process
> >> since the assembly code which runs at the fag end of the suspend
> >> process runs out of OCMC and hence we can't cut its clock.
> >>
> >> On AM335x, the OCMC clock is cut to have PER power domain transition
> >> but that's done in the WKUP-M3 firmware when going down. During the
> >> wakeup sequence, WKUP-M3 re-enables the OCMC clock so that when the
> >> kernel resumes the h/w state is same.
> >
> > OK, but *today*, in *mainline*, where in the linux kernel (not the M3
> > firmware) is the OCMRAM clock cut during suspend?
> >
> > From what I can see, there is no driver for this device, so there are no
> > system PM calls being done for that device, and thus no omap_device
> > calls being done for that device, so the no_idle_on_suspend has no
> > effect.
> 
> OK, I think I confused things here, sorry. I was thinking runtime PM
> here, but wrote system PM.  The no_idle_on_suspend feature only affects
> system PM, and the omap_device calls will still be called during system
> PM, even without a driver.
> 
> That being said, the commit below[1], added in v3.6 should prevent the
> any automaic clock gating for devices without drivers bound.  Since
> there is no driver for the OCM RAM block, you shouldn't be affected by
> the automatic idle on suspend anyways.
> 
> So, my proposal is that Sourav remove that flag from the AM33xx hwmod
> when he removes this feature.
> 

Apologies for the delayed response. I was out of office for a couple of
days.

I don't recall the exact kernel version in which I ended up adding this flag
to keep the clock running but yes after the change mentioned below this flag
is not required. I just did a sanity check by removing this flag on v3.8
kernel and things work fine across suspend.

Regards,
Vaibhav 

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Sourav Poddar]

Hi Kevin,
On Thursday 11 April 2013 07:45 PM, Kevin Hilman wrote:
> Kevin Hilman<khilman@linaro.org>  writes:
>
>> "Bedia, Vaibhav"<vaibhav.bedia@ti.com>  writes:
>>
>>> Hi Sourav,
>>>
>>> On Wed, Apr 10, 2013 at 15:13:44, Poddar, Sourav wrote:
>>> [...]
>>>> Yes, had a look at that and found your situation similar to UART.
>>>>
>>>> But how exactly this gets used, I mean I don't  see any drivers/ in mainline
>>>> making use of this compatible string  "ti,am3352-ocmcram".  ?
>>> OCMC clock is enabled during bootup (not sure whether that's the h/w
>>> default or ROM does it) since the initial bootloader runs from there.
>>> By marking the corresponding hwmod with HWMOD_INIT_NO_IDLE we leave the
>>> clock running. Right now the sram code under arch/arm/plat-omap/ is what
>>> manages the OCMC. I guess this needs to move somewhere under drivers/
>>> and start managing the clocks. Even then we'll need a mechanism
>>> to leave the clocks running as part of the kernel suspend process
>>> since the assembly code which runs at the fag end of the suspend
>>> process runs out of OCMC and hence we can't cut its clock.
>>>
>>> On AM335x, the OCMC clock is cut to have PER power domain transition
>>> but that's done in the WKUP-M3 firmware when going down. During the
>>> wakeup sequence, WKUP-M3 re-enables the OCMC clock so that when the
>>> kernel resumes the h/w state is same.
>> OK, but *today*, in *mainline*, where in the linux kernel (not the M3
>> firmware) is the OCMRAM clock cut during suspend?
>>
>>  From what I can see, there is no driver for this device, so there are no
>> system PM calls being done for that device, and thus no omap_device
>> calls being done for that device, so the no_idle_on_suspend has no
>> effect.
> OK, I think I confused things here, sorry. I was thinking runtime PM
> here, but wrote system PM.  The no_idle_on_suspend feature only affects
> system PM, and the omap_device calls will still be called during system
> PM, even without a driver.
>
> That being said, the commit below[1], added in v3.6 should prevent the
> any automaic clock gating for devices without drivers bound.  Since
> there is no driver for the OCM RAM block, you shouldn't be affected by
> the automatic idle on suspend anyways.
>
> So, my proposal is that Sourav remove that flag from the AM33xx hwmod
> when he removes this feature.
>
> Kevin
>
Thanks a lot for your inputs and helping in bringing this thread to
a logical conclusion.

I will post a v4 for this patch along with other fixes/cleanups
required as recommended by you and russell.

Thanks,
Sourav
> [1]
> commit 72bb6f9b51c82c820ddef892455a85b115460904
> Author: Kevin Hilman<khilman@ti.com>
> Date:   Tue Jul 10 15:29:04 2012 -0700
>
>      ARM: OMAP: omap_device: don't attempt late suspend if no driver bound
>
>      Currently, the omap_device PM domain layer uses the late suspend and
>      early resume callbacks to ensure devices are in their low power
>      states.
>
>      However, this is attempted even in cases where a driver probe has
>      failed.  If a driver's ->probe() method fails, the driver is likely in
>      a state where it is not expecting its runtime PM callbacks to be
>      called, yet currently the omap_device PM domain code attempts to call
>      the drivers callbacks.
>
>      To fix, use the omap_device driver_status field to check whether a
>      driver is bound to the omap_device before attempting to trigger driver
>      callbacks.
>
>      Reviewed-by: Paul Walmsley<paul@pwsan.com>
>      Signed-off-by: Kevin Hilman<khilman@ti.com>

Re: [PATCHv3] driver: serial: prevent UART console idle on suspend while using "no_console_suspend"

[Kevin Hilman]

Hi Vaibhav,

"Bedia, Vaibhav" <vaibhav.bedia@ti.com> writes:

[...]

>> So, my proposal is that Sourav remove that flag from the AM33xx hwmod
>> when he removes this feature.
>
> Apologies for the delayed response. I was out of office for a couple of
> days.
>
> I don't recall the exact kernel version in which I ended up adding
> this flag to keep the clock running but yes after the change mentioned
> below this flag is not required. I just did a sanity check by removing
> this flag on v3.8 kernel and things work fine across suspend.

Great, thanks for checking. 

That leaves only the UART driver, so after Sourav's changes, we will
drop the flag completely.

Kevin