[RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Sourav Poddar]

Greg's tty-next is not booting on 2420 based N800. The failure is
observed at serial init itself. The reason might be that n800 tries to
resume even though it is not suspended before.

Reported-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
---
This patch is developed on top of greg's tty-next branch
CommitId: e740d8f tty: serial: Samsung: Fix return value +
the following patch which I have already posted to the mailing list.
http://comments.gmane.org/gmane.linux.ports.arm.omap/84729

 drivers/tty/serial/omap-serial.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 3c05c5e..bc355f2 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -110,6 +110,7 @@ struct uart_omap_port {
 	u32			calc_latency;
 	struct work_struct	qos_work;
 	struct pinctrl		*pins;
+	unsigned int		suspended:1;
 };
 
 #define to_uart_omap_port(p)	((container_of((p), struct uart_omap_port, port)))
@@ -1545,14 +1546,20 @@ static int serial_omap_runtime_suspend(struct device *dev)
 	up->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
 	schedule_work(&up->qos_work);
 
+	up->suspended = true;
+
 	return 0;
 }
 
 static int serial_omap_runtime_resume(struct device *dev)
 {
 	struct uart_omap_port *up = dev_get_drvdata(dev);
+	u32 loss_cnt;
+
+	if (!up->suspended)
+		return 0;
 
-	u32 loss_cnt = serial_omap_get_context_loss_count(up);
+	loss_cnt = serial_omap_get_context_loss_count(up);
 
 	if (up->context_loss_cnt != loss_cnt)
 		serial_omap_restore_context(up);
@@ -1560,6 +1567,8 @@ static int serial_omap_runtime_resume(struct device *dev)
 	up->latency = up->calc_latency;
 	schedule_work(&up->qos_work);
 
+	up->suspended = false;
+
 	return 0;
 }
 #endif
-- 
1.7.1

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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On Tue, Sep 18, 2012 at 06:10:50PM +0530, Sourav Poddar wrote:
> Greg's tty-next is not booting on 2420 based N800. The failure is
> observed at serial init itself. The reason might be that n800 tries to
> resume even though it is not suspended before.
> 
> Reported-by: Paul Walmsley <paul@pwsan.com>
> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>

FWIW:

Reviewed-by: Felipe Balbi <balbi@ti.com>

Paul does this fix the issue for you ? Note that it depends on a
previous patch Sourav sent [1]

[1] http://marc.info/?l=linux-omap&m=134796819607889&w=2

There's one thing that gets my attention, though, why only n800 would
fail here ?

I wonder if we should be using:

pm_runtime_set_active(dev);
pm_runtime_get_enable(dev);

to prevent our runtime_resume() to be called from probe, but Sourav
tested and it doesn't work on BeagleBoard, but it works on PandaBoard.

Does it ring any bell ??

> ---
> This patch is developed on top of greg's tty-next branch
> CommitId: e740d8f tty: serial: Samsung: Fix return value +
> the following patch which I have already posted to the mailing list.
> http://comments.gmane.org/gmane.linux.ports.arm.omap/84729
> 
>  drivers/tty/serial/omap-serial.c |   11 ++++++++++-
>  1 files changed, 10 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index 3c05c5e..bc355f2 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -110,6 +110,7 @@ struct uart_omap_port {
>  	u32			calc_latency;
>  	struct work_struct	qos_work;
>  	struct pinctrl		*pins;
> +	unsigned int		suspended:1;
>  };
>  
>  #define to_uart_omap_port(p)	((container_of((p), struct uart_omap_port, port)))
> @@ -1545,14 +1546,20 @@ static int serial_omap_runtime_suspend(struct device *dev)
>  	up->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
>  	schedule_work(&up->qos_work);
>  
> +	up->suspended = true;
> +
>  	return 0;
>  }
>  
>  static int serial_omap_runtime_resume(struct device *dev)
>  {
>  	struct uart_omap_port *up = dev_get_drvdata(dev);
> +	u32 loss_cnt;
> +
> +	if (!up->suspended)
> +		return 0;
>  
> -	u32 loss_cnt = serial_omap_get_context_loss_count(up);
> +	loss_cnt = serial_omap_get_context_loss_count(up);
>  
>  	if (up->context_loss_cnt != loss_cnt)
>  		serial_omap_restore_context(up);
> @@ -1560,6 +1567,8 @@ static int serial_omap_runtime_resume(struct device *dev)
>  	up->latency = up->calc_latency;
>  	schedule_work(&up->qos_work);
>  
> +	up->suspended = false;
> +
>  	return 0;
>  }
>  #endif
> -- 
> 1.7.1
> 

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Paul Walmsley]

On Tue, 18 Sep 2012, Felipe Balbi wrote:

> On Tue, Sep 18, 2012 at 06:10:50PM +0530, Sourav Poddar wrote:
> > Greg's tty-next is not booting on 2420 based N800. The failure is
> > observed at serial init itself. The reason might be that n800 tries to
> > resume even though it is not suspended before.
> > 
> > Reported-by: Paul Walmsley <paul@pwsan.com>
> > Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
> 
> FWIW:
> 
> Reviewed-by: Felipe Balbi <balbi@ti.com>
> 
> Paul does this fix the issue for you ? Note that it depends on a
> previous patch Sourav sent [1]
> 
> [1] http://marc.info/?l=linux-omap&m=134796819607889&w=2

Yes, thanks - that fixes it,

Tested-by: Paul Walmsley <paul@pwsan.com>

> There's one thing that gets my attention, though, why only n800 would
> fail here ?
> 
> I wonder if we should be using:
> 
> pm_runtime_set_active(dev);
> pm_runtime_get_enable(dev);
> 
> to prevent our runtime_resume() to be called from probe, but Sourav
> tested and it doesn't work on BeagleBoard, but it works on PandaBoard.
> 
> Does it ring any bell ??

Nothing off the top of my head but haven't looked into it -- maybe this 
rings a bell with Kevin?


- Paul

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Grazvydas Ignotas]

On Tue, Sep 18, 2012 at 5:02 PM, Felipe Balbi <balbi@ti.com> wrote:
> On Tue, Sep 18, 2012 at 06:10:50PM +0530, Sourav Poddar wrote:
>> Greg's tty-next is not booting on 2420 based N800. The failure is
>> observed at serial init itself. The reason might be that n800 tries to
>> resume even though it is not suspended before.
>>
>> Reported-by: Paul Walmsley <paul@pwsan.com>
>> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
>
> FWIW:
>
> Reviewed-by: Felipe Balbi <balbi@ti.com>
>
> Paul does this fix the issue for you ? Note that it depends on a
> previous patch Sourav sent [1]
>
> [1] http://marc.info/?l=linux-omap&m=134796819607889&w=2
>
> There's one thing that gets my attention, though, why only n800 would
> fail here ?
>
> I wonder if we should be using:
>
> pm_runtime_set_active(dev);
> pm_runtime_get_enable(dev);
>
> to prevent our runtime_resume() to be called from probe, but Sourav
> tested and it doesn't work on BeagleBoard, but it works on PandaBoard.
>
> Does it ring any bell ??

Well I guess it's normal resume callback is called during probe as
pm_runtime_get_sync() is called there, and according to documentation
[1], devices are assumed to be suspended before probe is called.

According to [1], pm_runtime_set_active() should be called before
pm_runtime_enable() to indicate to the core that device is active
during probe if that's the case, I guess this means
pm_runtime_get_sync() is not needed in that case, but I'm not sure
what's the actual serial state during probe nowadays.

[1] chapter 5 of Documentation/power/runtime_pm.txt:
The initial runtime PM status of all devices is 'suspended', but it
need not reflect the actual physical state of the device. Thus, if the
device is initially active (i.e. it is able to process I/O), its
runtime PM status must be changed to 'active', with the help of
pm_runtime_set_active(), before pm_runtime_enable() is called for the
device.

-- 
Gražvydas

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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On Wed, Sep 19, 2012 at 02:52:18PM +0300, Grazvydas Ignotas wrote:
> On Tue, Sep 18, 2012 at 5:02 PM, Felipe Balbi <balbi@ti.com> wrote:
> > On Tue, Sep 18, 2012 at 06:10:50PM +0530, Sourav Poddar wrote:
> >> Greg's tty-next is not booting on 2420 based N800. The failure is
> >> observed at serial init itself. The reason might be that n800 tries to
> >> resume even though it is not suspended before.
> >>
> >> Reported-by: Paul Walmsley <paul@pwsan.com>
> >> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
> >
> > FWIW:
> >
> > Reviewed-by: Felipe Balbi <balbi@ti.com>
> >
> > Paul does this fix the issue for you ? Note that it depends on a
> > previous patch Sourav sent [1]
> >
> > [1] http://marc.info/?l=linux-omap&m=134796819607889&w=2
> >
> > There's one thing that gets my attention, though, why only n800 would
> > fail here ?
> >
> > I wonder if we should be using:
> >
> > pm_runtime_set_active(dev);
> > pm_runtime_get_enable(dev);
> >
> > to prevent our runtime_resume() to be called from probe, but Sourav
> > tested and it doesn't work on BeagleBoard, but it works on PandaBoard.
> >
> > Does it ring any bell ??
> 
> Well I guess it's normal resume callback is called during probe as
> pm_runtime_get_sync() is called there, and according to documentation
> [1], devices are assumed to be suspended before probe is called.
> 
> According to [1], pm_runtime_set_active() should be called before
> pm_runtime_enable() to indicate to the core that device is active
> during probe if that's the case, I guess this means
> pm_runtime_get_sync() is not needed in that case, but I'm not sure
> what's the actual serial state during probe nowadays.
> 
> [1] chapter 5 of Documentation/power/runtime_pm.txt:
> The initial runtime PM status of all devices is 'suspended', but it
> need not reflect the actual physical state of the device. Thus, if the
> device is initially active (i.e. it is able to process I/O), its
> runtime PM status must be changed to 'active', with the help of
> pm_runtime_set_active(), before pm_runtime_enable() is called for the
> device.

this is what I mean, actually. If we remove pm_runtime_get_sync() in
exchange for pm_runtime_set_active() before pm_runtime_enable(), it
works on PandaBoard, but breaks BeagleBoard.

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Poddar, Sourav]

Hi Greg,

Ping on this?

On Tue, Sep 18, 2012 at 6:10 PM, Sourav Poddar <sourav.poddar@ti.com> wrote:
> Greg's tty-next is not booting on 2420 based N800. The failure is
> observed at serial init itself. The reason might be that n800 tries to
> resume even though it is not suspended before.
>
> Reported-by: Paul Walmsley <paul@pwsan.com>
> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
> ---
> This patch is developed on top of greg's tty-next branch
> CommitId: e740d8f tty: serial: Samsung: Fix return value +
> the following patch which I have already posted to the mailing list.
> http://comments.gmane.org/gmane.linux.ports.arm.omap/84729
>
>  drivers/tty/serial/omap-serial.c |   11 ++++++++++-
>  1 files changed, 10 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index 3c05c5e..bc355f2 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -110,6 +110,7 @@ struct uart_omap_port {
>         u32                     calc_latency;
>         struct work_struct      qos_work;
>         struct pinctrl          *pins;
> +       unsigned int            suspended:1;
>  };
>
>  #define to_uart_omap_port(p)   ((container_of((p), struct uart_omap_port, port)))
> @@ -1545,14 +1546,20 @@ static int serial_omap_runtime_suspend(struct device *dev)
>         up->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
>         schedule_work(&up->qos_work);
>
> +       up->suspended = true;
> +
>         return 0;
>  }
>
>  static int serial_omap_runtime_resume(struct device *dev)
>  {
>         struct uart_omap_port *up = dev_get_drvdata(dev);
> +       u32 loss_cnt;
> +
> +       if (!up->suspended)
> +               return 0;
>
> -       u32 loss_cnt = serial_omap_get_context_loss_count(up);
> +       loss_cnt = serial_omap_get_context_loss_count(up);
>
>         if (up->context_loss_cnt != loss_cnt)
>                 serial_omap_restore_context(up);
> @@ -1560,6 +1567,8 @@ static int serial_omap_runtime_resume(struct device *dev)
>         up->latency = up->calc_latency;
>         schedule_work(&up->qos_work);
>
> +       up->suspended = false;
> +
>         return 0;
>  }
>  #endif
> --
> 1.7.1
>

~Sourav

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 01:52:03PM +0530, Poddar, Sourav wrote:
> Hi Greg,
> 
> Ping on this?
> 
> On Tue, Sep 18, 2012 at 6:10 PM, Sourav Poddar <sourav.poddar@ti.com> wrote:
> > Greg's tty-next is not booting on 2420 based N800. The failure is
> > observed at serial init itself. The reason might be that n800 tries to
> > resume even though it is not suspended before.

How is this happening?  I think that needs proper investigation - or if
it's had more investigation, then the results needs to be included in
the commit description so that everyone can understand the issue here.

We should not be resuming a device which hasn't been suspended.  Maybe
the runtime PM enable sequence is wrong, and that's what should be fixed
instead?  

This sequence in the probe() function:

        pm_runtime_irq_safe(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        pm_runtime_get_sync(&pdev->dev);

would enable runtime PM while the s/w state indicates that it's disabled,
and then that pm_runtime_get_sync() will want to resume the device.  See
the section "5. Runtime PM Initialization, Device Probing and Removal"
in Documentation/power/runtime_pm.txt, specifically the second paragraph
of that section.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> On Tue, Sep 25, 2012 at 01:52:03PM +0530, Poddar, Sourav wrote:
> > Hi Greg,
> > 
> > Ping on this?
> > 
> > On Tue, Sep 18, 2012 at 6:10 PM, Sourav Poddar <sourav.poddar@ti.com> wrote:
> > > Greg's tty-next is not booting on 2420 based N800. The failure is
> > > observed at serial init itself. The reason might be that n800 tries to
> > > resume even though it is not suspended before.
> 
> How is this happening?  I think that needs proper investigation - or if
> it's had more investigation, then the results needs to be included in
> the commit description so that everyone can understand the issue here.
> 
> We should not be resuming a device which hasn't been suspended.  Maybe
> the runtime PM enable sequence is wrong, and that's what should be fixed
> instead?  
> 
> This sequence in the probe() function:
> 
>         pm_runtime_irq_safe(&pdev->dev);
>         pm_runtime_enable(&pdev->dev);
>         pm_runtime_get_sync(&pdev->dev);
> 
> would enable runtime PM while the s/w state indicates that it's disabled,
> and then that pm_runtime_get_sync() will want to resume the device.  See
> the section "5. Runtime PM Initialization, Device Probing and Removal"
> in Documentation/power/runtime_pm.txt, specifically the second paragraph
> of that section.

that was tested. It worked in pandaboard but didn't work on beagleboard
XM. Sourav tried to start a discussion about that, but it simply died...

In any case, pm_runtime_get_sync() in probe will always call
runtime_resume callback, right ?

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
> On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > > How is this happening?  I think that needs proper investigation - or if
> > > it's had more investigation, then the results needs to be included in
> > > the commit description so that everyone can understand the issue here.
> > > 
> > > We should not be resuming a device which hasn't been suspended.  Maybe
> > > the runtime PM enable sequence is wrong, and that's what should be fixed
> > > instead?  
> > > 
> > > This sequence in the probe() function:
> > > 
> > >         pm_runtime_irq_safe(&pdev->dev);
> > >         pm_runtime_enable(&pdev->dev);
> > >         pm_runtime_get_sync(&pdev->dev);
> > > 
> > > would enable runtime PM while the s/w state indicates that it's disabled,
> > > and then that pm_runtime_get_sync() will want to resume the device.  See
> > > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > > of that section.
> > 
> > that was tested. It worked in pandaboard but didn't work on beagleboard
> > XM. Sourav tried to start a discussion about that, but it simply died...
> > 
> > In any case, pm_runtime_get_sync() in probe will always call
> > runtime_resume callback, right ?
> 
> Well, if the runtime PM state says it's suspended, and then you enable
> runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
> attempt.  The patch description is complaining about resume events without
> there being a preceding suspend event.
> 
> This could well be why.

that's most likely, of course. But should we cause a regression to
beagleboard XM because of that ? Also, if you look into chapter 9 of the
runtime_pm documentation, starting on line 822 you'll see documentation
suggests the use of mystruct->is_suspended flag.

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > How is this happening?  I think that needs proper investigation - or if
> > it's had more investigation, then the results needs to be included in
> > the commit description so that everyone can understand the issue here.
> > 
> > We should not be resuming a device which hasn't been suspended.  Maybe
> > the runtime PM enable sequence is wrong, and that's what should be fixed
> > instead?  
> > 
> > This sequence in the probe() function:
> > 
> >         pm_runtime_irq_safe(&pdev->dev);
> >         pm_runtime_enable(&pdev->dev);
> >         pm_runtime_get_sync(&pdev->dev);
> > 
> > would enable runtime PM while the s/w state indicates that it's disabled,
> > and then that pm_runtime_get_sync() will want to resume the device.  See
> > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > of that section.
> 
> that was tested. It worked in pandaboard but didn't work on beagleboard
> XM. Sourav tried to start a discussion about that, but it simply died...
> 
> In any case, pm_runtime_get_sync() in probe will always call
> runtime_resume callback, right ?

Well, if the runtime PM state says it's suspended, and then you enable
runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
attempt.  The patch description is complaining about resume events without
there being a preceding suspend event.

This could well be why.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
> On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
> > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > > > How is this happening?  I think that needs proper investigation - or if
> > > > it's had more investigation, then the results needs to be included in
> > > > the commit description so that everyone can understand the issue here.
> > > > 
> > > > We should not be resuming a device which hasn't been suspended.  Maybe
> > > > the runtime PM enable sequence is wrong, and that's what should be fixed
> > > > instead?  
> > > > 
> > > > This sequence in the probe() function:
> > > > 
> > > >         pm_runtime_irq_safe(&pdev->dev);
> > > >         pm_runtime_enable(&pdev->dev);
> > > >         pm_runtime_get_sync(&pdev->dev);
> > > > 
> > > > would enable runtime PM while the s/w state indicates that it's disabled,
> > > > and then that pm_runtime_get_sync() will want to resume the device.  See
> > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > > > of that section.
> > > 
> > > that was tested. It worked in pandaboard but didn't work on beagleboard
> > > XM. Sourav tried to start a discussion about that, but it simply died...
> > > 
> > > In any case, pm_runtime_get_sync() in probe will always call
> > > runtime_resume callback, right ?
> > 
> > Well, if the runtime PM state says it's suspended, and then you enable
> > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
> > attempt.  The patch description is complaining about resume events without
> > there being a preceding suspend event.
> > 
> > This could well be why.
> 
> that's most likely, of course. But should we cause a regression to
> beagleboard XM because of that ?

What would cause a regression on beagleboard XM?  I have not suggested
any change other than more investigation of the issue and a fuller patch
description - yet you're screaming (idiotically IMHO) that mere
investigation would break beagleboard.

Well, if it's _that_ fragile, that mere investigation of this issue by
someone elsewhere on the planet would break your beagleboard, maybe it
deserves to be broken!

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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Hi,

On Tue, Sep 25, 2012 at 10:21:18AM +0100, Russell King - ARM Linux wrote:
> On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
> > On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
> > > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> > > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > > > > How is this happening?  I think that needs proper investigation - or if
> > > > > it's had more investigation, then the results needs to be included in
> > > > > the commit description so that everyone can understand the issue here.
> > > > > 
> > > > > We should not be resuming a device which hasn't been suspended.  Maybe
> > > > > the runtime PM enable sequence is wrong, and that's what should be fixed
> > > > > instead?  
> > > > > 
> > > > > This sequence in the probe() function:
> > > > > 
> > > > >         pm_runtime_irq_safe(&pdev->dev);
> > > > >         pm_runtime_enable(&pdev->dev);
> > > > >         pm_runtime_get_sync(&pdev->dev);
> > > > > 
> > > > > would enable runtime PM while the s/w state indicates that it's disabled,
> > > > > and then that pm_runtime_get_sync() will want to resume the device.  See
> > > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > > > > of that section.
> > > > 
> > > > that was tested. It worked in pandaboard but didn't work on beagleboard
> > > > XM. Sourav tried to start a discussion about that, but it simply died...
> > > > 
> > > > In any case, pm_runtime_get_sync() in probe will always call
> > > > runtime_resume callback, right ?
> > > 
> > > Well, if the runtime PM state says it's suspended, and then you enable
> > > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
> > > attempt.  The patch description is complaining about resume events without
> > > there being a preceding suspend event.
> > > 
> > > This could well be why.
> > 
> > that's most likely, of course. But should we cause a regression to
> > beagleboard XM because of that ?
> 
> What would cause a regression on beagleboard XM?  I have not suggested
> any change other than more investigation of the issue and a fuller patch
> description - yet you're screaming (idiotically IMHO) that mere
> investigation would break beagleboard.
> 
> Well, if it's _that_ fragile, that mere investigation of this issue by
> someone elsewhere on the planet would break your beagleboard, maybe it
> deserves to be broken!

why are you always so over the top like that ? This is just
counter-productive to say the least.

What I'm trying to say here, is that there might be a bug either on pm
core or on OMAP3's implementation and I'd like to get input from Tony,
Santosh, Paul, etc before going forward. Maybe it's something they've
already been through, or maybe it rings a bell and points to somewhere
we should look for.

anyway, instead of feeding your ego, we can stop this discussion and let
Sourav see what he can come up with.

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Poddar, Sourav]

Hi,

On Tue, Sep 25, 2012 at 2:51 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
>> On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
>> > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
>> > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
>> > > > How is this happening?  I think that needs proper investigation - or if
>> > > > it's had more investigation, then the results needs to be included in
>> > > > the commit description so that everyone can understand the issue here.
>> > > >
>> > > > We should not be resuming a device which hasn't been suspended.  Maybe
>> > > > the runtime PM enable sequence is wrong, and that's what should be fixed
>> > > > instead?
>> > > >
>> > > > This sequence in the probe() function:
>> > > >
>> > > >         pm_runtime_irq_safe(&pdev->dev);
>> > > >         pm_runtime_enable(&pdev->dev);
>> > > >         pm_runtime_get_sync(&pdev->dev);
>> > > >
>> > > > would enable runtime PM while the s/w state indicates that it's disabled,
>> > > > and then that pm_runtime_get_sync() will want to resume the device.  See
>> > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
>> > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
>> > > > of that section.
>> > >
>> > > that was tested. It worked in pandaboard but didn't work on beagleboard
>> > > XM. Sourav tried to start a discussion about that, but it simply died...
>> > >
>> > > In any case, pm_runtime_get_sync() in probe will always call
>> > > runtime_resume callback, right ?
>> >
>> > Well, if the runtime PM state says it's suspended, and then you enable
>> > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
>> > attempt.  The patch description is complaining about resume events without
>> > there being a preceding suspend event.
>> >
>> > This could well be why.
>>
>> that's most likely, of course. But should we cause a regression to
>> beagleboard XM because of that ?
>
> What would cause a regression on beagleboard XM?  I have not suggested
> any change other than more investigation of the issue and a fuller patch
> description - yet you're screaming (idiotically IMHO) that mere
> investigation would break beagleboard.
>
> Well, if it's _that_ fragile, that mere investigation of this issue by
> someone elsewhere on the planet would break your beagleboard, maybe it
> deserves to be broken!

The issue was observed at serial init itself in the N800 board and the
log does not
show up much.
http://www.pwsan.com/omap/testlogs/test_tty_next_e36851d0/20120910020323/boot/2420n800/2420n800_log.txt
 What we thought the problem might be with n800 is that it tries to
resume when it didn't suspend before.

There are two ways through which we thought of handling this issue:

a) set device as active before enabling pm (which will prevent

pm_runtime_set_active(dev);
pm_runtime_enable(dev);

OR

b) adding a "suspended" flag to struct omap_uart_port which gets set on
suspend and cleared on resume. Then on resume you can check:

if (!up->suspended)
        return 0;

But using "pm_runtime_set_active" approach breaks things even on
beagle board xm,  though
it works fine on Panda.
Therefore, we used the "suspended" flag approach.

So. I just wanted to get some feedback from community about how using
"pm_runtime_set_active"
behaves differently in omap3 and omap4.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 12:48:16PM +0300, Felipe Balbi wrote:
> Hi,
> 
> On Tue, Sep 25, 2012 at 10:21:18AM +0100, Russell King - ARM Linux wrote:
> > On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
> > > On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
> > > > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> > > > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > > > > > How is this happening?  I think that needs proper investigation - or if
> > > > > > it's had more investigation, then the results needs to be included in
> > > > > > the commit description so that everyone can understand the issue here.
> > > > > > 
> > > > > > We should not be resuming a device which hasn't been suspended.  Maybe
> > > > > > the runtime PM enable sequence is wrong, and that's what should be fixed
> > > > > > instead?  
> > > > > > 
> > > > > > This sequence in the probe() function:
> > > > > > 
> > > > > >         pm_runtime_irq_safe(&pdev->dev);
> > > > > >         pm_runtime_enable(&pdev->dev);
> > > > > >         pm_runtime_get_sync(&pdev->dev);
> > > > > > 
> > > > > > would enable runtime PM while the s/w state indicates that it's disabled,
> > > > > > and then that pm_runtime_get_sync() will want to resume the device.  See
> > > > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > > > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > > > > > of that section.
> > > > > 
> > > > > that was tested. It worked in pandaboard but didn't work on beagleboard
> > > > > XM. Sourav tried to start a discussion about that, but it simply died...
> > > > > 
> > > > > In any case, pm_runtime_get_sync() in probe will always call
> > > > > runtime_resume callback, right ?
> > > > 
> > > > Well, if the runtime PM state says it's suspended, and then you enable
> > > > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
> > > > attempt.  The patch description is complaining about resume events without
> > > > there being a preceding suspend event.
> > > > 
> > > > This could well be why.
> > > 
> > > that's most likely, of course. But should we cause a regression to
> > > beagleboard XM because of that ?
> > 
> > What would cause a regression on beagleboard XM?  I have not suggested
> > any change other than more investigation of the issue and a fuller patch
> > description - yet you're screaming (idiotically IMHO) that mere
> > investigation would break beagleboard.
> > 
> > Well, if it's _that_ fragile, that mere investigation of this issue by
> > someone elsewhere on the planet would break your beagleboard, maybe it
> > deserves to be broken!
> 
> why are you always so over the top like that ? This is just
> counter-productive to say the least.

Because you are accusing me of potentially breaking your beagleboard
for merely suggesting further investigation and a better commit message.

You are the one going over the top, not me.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

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On Tue, Sep 25, 2012 at 11:29:58AM +0100, Russell King - ARM Linux wrote:
> On Tue, Sep 25, 2012 at 12:48:16PM +0300, Felipe Balbi wrote:
> > Hi,
> > 
> > On Tue, Sep 25, 2012 at 10:21:18AM +0100, Russell King - ARM Linux wrote:
> > > On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
> > > > On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
> > > > > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
> > > > > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
> > > > > > > How is this happening?  I think that needs proper investigation - or if
> > > > > > > it's had more investigation, then the results needs to be included in
> > > > > > > the commit description so that everyone can understand the issue here.
> > > > > > > 
> > > > > > > We should not be resuming a device which hasn't been suspended.  Maybe
> > > > > > > the runtime PM enable sequence is wrong, and that's what should be fixed
> > > > > > > instead?  
> > > > > > > 
> > > > > > > This sequence in the probe() function:
> > > > > > > 
> > > > > > >         pm_runtime_irq_safe(&pdev->dev);
> > > > > > >         pm_runtime_enable(&pdev->dev);
> > > > > > >         pm_runtime_get_sync(&pdev->dev);
> > > > > > > 
> > > > > > > would enable runtime PM while the s/w state indicates that it's disabled,
> > > > > > > and then that pm_runtime_get_sync() will want to resume the device.  See
> > > > > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
> > > > > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
> > > > > > > of that section.
> > > > > > 
> > > > > > that was tested. It worked in pandaboard but didn't work on beagleboard
> > > > > > XM. Sourav tried to start a discussion about that, but it simply died...
> > > > > > 
> > > > > > In any case, pm_runtime_get_sync() in probe will always call
> > > > > > runtime_resume callback, right ?
> > > > > 
> > > > > Well, if the runtime PM state says it's suspended, and then you enable
> > > > > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
> > > > > attempt.  The patch description is complaining about resume events without
> > > > > there being a preceding suspend event.
> > > > > 
> > > > > This could well be why.
> > > > 
> > > > that's most likely, of course. But should we cause a regression to
> > > > beagleboard XM because of that ?
> > > 
> > > What would cause a regression on beagleboard XM?  I have not suggested
> > > any change other than more investigation of the issue and a fuller patch
> > > description - yet you're screaming (idiotically IMHO) that mere
> > > investigation would break beagleboard.
> > > 
> > > Well, if it's _that_ fragile, that mere investigation of this issue by
> > > someone elsewhere on the planet would break your beagleboard, maybe it
> > > deserves to be broken!
> > 
> > why are you always so over the top like that ? This is just
> > counter-productive to say the least.
> 
> Because you are accusing me of potentially breaking your beagleboard
> for merely suggesting further investigation and a better commit message.

Where did I accuse you of anyting ? I just mentioned we experienced a
regression with beagleboard XM when using pm_runtime_set_active().

here's my quote:

> that was tested. It worked in pandaboard but didn't work on
> beagleboard XM. Sourav tried to start a discussion about that, but it
> simply died...

To add extra info, here you go:

We pinged Paul and asked if he had seen that before, he had no
pointers... Because Documentation/power/runtime_pm.txt was using a
mystruct->is_suspended flag, we just decided to follow the same
"design" since no-one was able to suggest why pm_runtime_set_active()
was breaking beagleXM nor how it was supposed to actually work.

Reading the code: pm_runtime_set_active() would tell pm_runtime core
the device is actually active by setting runtime_status to RPM_ACTIVE,
thus the following pm_runtime_get_sync() wouldn't actually call
runtime_resume() callback, but it would increment usage_counter.

I can't see why this would fail on beagleXM, but it does and we'd like
to hear in which situations this could fail...

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

Right, let's get this thread back onto a constructive footing and try
to understand the problems here.

On Tue, Sep 25, 2012 at 03:26:06PM +0530, Poddar, Sourav wrote:
> The issue was observed at serial init itself in the N800 board and the
> log does not show up much.
> http://www.pwsan.com/omap/testlogs/test_tty_next_e36851d0/20120910020323/boot/2420n800/2420n800_log.txt

Right, so output stops when ttyO2 is initialized.

> What we thought the problem might be with n800 is that it tries to
> resume when it didn't suspend before.
> 
> There are two ways through which we thought of handling this issue:
> 
> a) set device as active before enabling pm (which will prevent
> 
> pm_runtime_set_active(dev);
> pm_runtime_enable(dev);
> 
> OR
> 
> b) adding a "suspended" flag to struct omap_uart_port which gets set on
> suspend and cleared on resume. Then on resume you can check:
> 
> if (!up->suspended)
>         return 0;
> 
> But using "pm_runtime_set_active" approach breaks things even on
> beagle board xm, though it works fine on Panda.

Right, so now the question becomes - what is different on the Beagle Board
that prevents solution (a) from working - or put it another way, have we
uncovered _another_ bug.

For N800, for ttyO0 and ttyO1 which aren't in use, it may be correct.
We don't know for certain.  For ttyO2, the port is clearly already in
use as it's being used for console output.  So that means it's _not_
in suspended state, and therefore the initial runtime PM state is
wrong.

For Beagleboard - who knows, we have no information on that.  All we
know is that your (a) sequence causes a regression.

Anyway, let's analyse the code paths.  What is pm_runtime_get_sync()
doing?  Well, it calls __pm_runtime_resume(, RPM_GET_PUT).  That alters
the parent device's state (which doesn't matter for this, as the platform
device is a child of the main platform device, which has no runtime PM.)

It then calls the resume callback (from the pm domain/type/class/bus/
driver) and then does an idle check.

OMAP devices have a pm domain, so this is the candidate for the callback
at this level, which gets us into _od_runtime_resume().  This calls
omap_device_enable() before then moving on to the driver's runtime resume
method, and at that point the runtime PM resume is complete.

So, with your (a) solution, what's different is that we omit calling
omap_device_enable().  Therefore, my hunch is the reason that Beagleboard
doesn't work is because it doesn't like missing that call.

I bet if you do this:

	omap_device_enable(dev);
	pm_runtime_set_active(dev);
	pm_runtime_enable(dev);

that this will solve your problem, and Beagleboard will continue working.

What we have is a mismatch in both your case, and the Beagleboard case,
between the real state of the hardware, the runtime PM state, and the
OMAP hwmod state, and the above should bring all those states entirely
into line with each other for _every_ case.  It doesn't need any hacks
to prevent resume callbacks without prior suspends (which, incidentally,
the runtime PM core already guarantees provided you get the initial
state correct.)

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 01:37:03PM +0300, Felipe Balbi wrote:
> On Tue, Sep 25, 2012 at 11:29:58AM +0100, Russell King - ARM Linux wrote:
> > Because you are accusing me of potentially breaking your beagleboard
> > for merely suggesting further investigation and a better commit message.
> 
> Where did I accuse you of anyting ? I just mentioned we experienced a
> regression with beagleboard XM when using pm_runtime_set_active().

I quote:
:> But should we cause a regression to beagleboard XM because of that ?
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I say again: I was _only_ suggesting further investigation, yet you
were mouthing off about causing a regression to beagleboard "because
of that", effectively saying that no, we should not do any further
investigation and this is the only fix.

> To add extra info, here you go:

Finally, something constructive.

> We pinged Paul and asked if he had seen that before, he had no
> pointers... Because Documentation/power/runtime_pm.txt was using a
> mystruct->is_suspended flag, we just decided to follow the same
> "design" since no-one was able to suggest why pm_runtime_set_active()
> was breaking beagleXM nor how it was supposed to actually work.
> 
> Reading the code: pm_runtime_set_active() would tell pm_runtime core
> the device is actually active by setting runtime_status to RPM_ACTIVE,
> thus the following pm_runtime_get_sync() wouldn't actually call
> runtime_resume() callback, but it would increment usage_counter.
> 
> I can't see why this would fail on beagleXM, but it does and we'd like
> to hear in which situations this could fail...

Well, I've just spent five minutes analysing the code paths - which I
hadn't looked at before - and I've pointed out what's probably causing
the problem for Beagle.  I think you owe me an appology over your
aggressive attitude towards my suggestions that there needed to be
some further investigation.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 2943 bytes --]

Hi,

On Tue, Sep 25, 2012 at 12:07:03PM +0100, Russell King - ARM Linux wrote:
> On Tue, Sep 25, 2012 at 01:37:03PM +0300, Felipe Balbi wrote:
> > On Tue, Sep 25, 2012 at 11:29:58AM +0100, Russell King - ARM Linux wrote:
> > > Because you are accusing me of potentially breaking your beagleboard
> > > for merely suggesting further investigation and a better commit message.
> > 
> > Where did I accuse you of anyting ? I just mentioned we experienced a
> > regression with beagleboard XM when using pm_runtime_set_active().
> 
> I quote:
> :> But should we cause a regression to beagleboard XM because of that ?
>    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

maybe that wasn't the best way to put it, but I was trying to point out
that either there was a bug on pm core or omap_device/hwmod, not that we
shouldn't investigate.

> I say again: I was _only_ suggesting further investigation, yet you
> were mouthing off about causing a regression to beagleboard "because
> of that", effectively saying that no, we should not do any further
> investigation and this is the only fix.

not what I meant, but fair enough... The "because of that" was supposed
to mean "because of pm_runtime_set_active()". I find the documentation
for that particular call to be rather poor and a bit confusing,
specially when further down, the very same document uses a
"is_suspended" flag which, in fact, shouldn't be needed when we have
pm_runtime_is_suspended() and the like.

> > We pinged Paul and asked if he had seen that before, he had no
> > pointers... Because Documentation/power/runtime_pm.txt was using a
> > mystruct->is_suspended flag, we just decided to follow the same
> > "design" since no-one was able to suggest why pm_runtime_set_active()
> > was breaking beagleXM nor how it was supposed to actually work.
> > 
> > Reading the code: pm_runtime_set_active() would tell pm_runtime core
> > the device is actually active by setting runtime_status to RPM_ACTIVE,
> > thus the following pm_runtime_get_sync() wouldn't actually call
> > runtime_resume() callback, but it would increment usage_counter.
> > 
> > I can't see why this would fail on beagleXM, but it does and we'd like
> > to hear in which situations this could fail...
> 
> Well, I've just spent five minutes analysing the code paths - which I
> hadn't looked at before - and I've pointed out what's probably causing
> the problem for Beagle.  I think you owe me an appology over your
> aggressive attitude towards my suggestions that there needed to be
> some further investigation.

I don't see any aggressive attitude towards what you suggested,
actually. Mailing list archives are available to check, but the one
cursing around was always yourself and THAT deserves an apology.

If you still think I've been at all aggressive, then sure, I apologize,
it wasn't what I meant though.

-- 
balbi

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Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
> that's most likely, of course. But should we cause a regression to
> beagleboard XM because of that ? Also, if you look into chapter 9 of the
> runtime_pm documentation, starting on line 822 you'll see documentation
> suggests the use of mystruct->is_suspended flag.

BTW, I'll point out a fatal flaw in your justification above.

If you read the entire example, you'll see that the is_suspended flag
is _not_ used to prevent resumes without suspends, but is used as a
flag to control whether the driver processes requests or not.  That's
entirely functionally different from using a "is_suspended" flag in
the way you mention above.

Section 5 is quite clear about the requirements at initialization time
for runtime PM, and nothing in section 9 contradicts that, and the
is_suspended flag in that example has nothing to do with any of this.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Tue, Sep 25, 2012 at 02:12:43PM +0300, Felipe Balbi wrote:
> I don't see any aggressive attitude towards what you suggested,
> actually. Mailing list archives are available to check, but the one
> cursing around was always yourself and THAT deserves an apology.

Total rubbish.  No apology, because I wasn't cursing you.  Whatever,
I'm not going to re-explain the email thread.

What I said was that your raising of beagleboard breakage (twice) was
idiotic to a request for investigation.  That's a statement I _still_
fully agree with, and I'll say it again if I have to.

Trying to shut down investigation because investigation may break
something _is_ idiotic - especially if the investigation reveals
potential reasons why that breakage would occur.  Further investigation
is precisely how we arrive at better solutions.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Jassi Brar]

On 19 September 2012 17:29, Felipe Balbi <balbi@ti.com> wrote:

> this is what I mean, actually. If we remove pm_runtime_get_sync() in
> exchange for pm_runtime_set_active() before pm_runtime_enable(), it
> works on PandaBoard, but breaks BeagleBoard.
>
Perhaps it suggests that OMAP4 (PandaBoard) serial port is already
activated but OMAP3 (BeagleBoard) isn't. So we need to reflect that
either by doing pm_runtime_set_active() only on OMAP4 or by bringing
up the OMAP3 too before the pm_runtime_set_active() call.
BTW I understand get_sync(), set_active() and enable() are for
different purposes, they can't be traded for one another.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Greg KH]

On Tue, Sep 25, 2012 at 01:52:03PM +0530, Poddar, Sourav wrote:
> Hi Greg,
> 
> Ping on this?

It was a RFT patch, with a huge thread.  What's the resolution here?
Did people figure out the real problem here or not?  If so, care to
resend the proper patch so I know what to apply?

thanks,

greg k-h

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Kevin Hilman]

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

> Hi,
>
> On Tue, Sep 25, 2012 at 2:51 PM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
>> On Tue, Sep 25, 2012 at 12:11:14PM +0300, Felipe Balbi wrote:
>>> On Tue, Sep 25, 2012 at 10:12:28AM +0100, Russell King - ARM Linux wrote:
>>> > On Tue, Sep 25, 2012 at 11:31:20AM +0300, Felipe Balbi wrote:
>>> > > On Tue, Sep 25, 2012 at 09:30:29AM +0100, Russell King - ARM Linux wrote:
>>> > > > How is this happening?  I think that needs proper investigation - or if
>>> > > > it's had more investigation, then the results needs to be included in
>>> > > > the commit description so that everyone can understand the issue here.
>>> > > >
>>> > > > We should not be resuming a device which hasn't been suspended.  Maybe
>>> > > > the runtime PM enable sequence is wrong, and that's what should be fixed
>>> > > > instead?
>>> > > >
>>> > > > This sequence in the probe() function:
>>> > > >
>>> > > >         pm_runtime_irq_safe(&pdev->dev);
>>> > > >         pm_runtime_enable(&pdev->dev);
>>> > > >         pm_runtime_get_sync(&pdev->dev);
>>> > > >
>>> > > > would enable runtime PM while the s/w state indicates that it's disabled,
>>> > > > and then that pm_runtime_get_sync() will want to resume the device.  See
>>> > > > the section "5. Runtime PM Initialization, Device Probing and Removal"
>>> > > > in Documentation/power/runtime_pm.txt, specifically the second paragraph
>>> > > > of that section.
>>> > >
>>> > > that was tested. It worked in pandaboard but didn't work on beagleboard
>>> > > XM. Sourav tried to start a discussion about that, but it simply died...
>>> > >
>>> > > In any case, pm_runtime_get_sync() in probe will always call
>>> > > runtime_resume callback, right ?
>>> >
>>> > Well, if the runtime PM state says it's suspended, and then you enable
>>> > runtime PM, the first call to pm_runtime_get_sync() will trigger a resume
>>> > attempt.  The patch description is complaining about resume events without
>>> > there being a preceding suspend event.
>>> >
>>> > This could well be why.
>>>
>>> that's most likely, of course. But should we cause a regression to
>>> beagleboard XM because of that ?
>>
>> What would cause a regression on beagleboard XM?  I have not suggested
>> any change other than more investigation of the issue and a fuller patch
>> description - yet you're screaming (idiotically IMHO) that mere
>> investigation would break beagleboard.
>>
>> Well, if it's _that_ fragile, that mere investigation of this issue by
>> someone elsewhere on the planet would break your beagleboard, maybe it
>> deserves to be broken!
>
> The issue was observed at serial init itself in the N800 board and the
> log does not
> show up much.
> http://www.pwsan.com/omap/testlogs/test_tty_next_e36851d0/20120910020323/boot/2420n800/2420n800_log.txt
>  What we thought the problem might be with n800 is that it tries to
> resume when it didn't suspend before.
>
> There are two ways through which we thought of handling this issue:
>
> a) set device as active before enabling pm (which will prevent
>
> pm_runtime_set_active(dev);
> pm_runtime_enable(dev);
>
> OR
>
> b) adding a "suspended" flag to struct omap_uart_port which gets set on
> suspend and cleared on resume. Then on resume you can check:
>
> if (!up->suspended)
>         return 0;
>
> But using "pm_runtime_set_active" approach breaks things even on
> beagle board xm,  though
> it works fine on Panda.
> Therefore, we used the "suspended" flag approach.
>
> So. I just wanted to get some feedback from community about how using
> "pm_runtime_set_active"
> behaves differently in omap3 and omap4.

As Russell has already pointed out in great detail, the difference is
simply a mismatch between assumed HW stated and actual hardware state
between various boards.  Put simply, the driver assumes the HW is
disabled (runtime suspended) when it loads, and the first runtime resume
is meant to enable the HW.  If that assumption is wrong, it needs to be
fixed.

Have you figured out why the HW is already active on OMAP2?  (probably
bootloader?)  

That being said, already active HW should not cause this problem.  In
fact, because of possible early console use, the hwmod init of the UART
hwmods does not idle/reset them on boot, so they are left in the state
that the bootloader set them in.  

When the hwmod is later enabled for real during probe, the hwmod muxing
is done for that IP.  So, I suspect what is really happening is that the
mux settings are not right for the UARTS on n800, so when the probe
happens, the UART mux settings are changed and you lose the UART.

Can you double check the UART mux settings for that board?  You might
need some different mux settings in the board file.

Kevin

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Paul Walmsley]

Hi Sourav, Felipe,

any progress on fixing the N800 problem?  Would be good to keep it booting 
since we use it as our primary 2420 test platform.


- Paul

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Sourav]

Hi Paul,

There are
On Thursday 11 October 2012 11:58 PM, Paul Walmsley wrote:
> Hi Sourav, Felipe,
>
> any progress on fixing the N800 problem?  Would be good to keep it booting
> since we use it as our primary 2420 test platform.
>
>
> - Paul
The patch sent inlined below might help us to get rid of the serial init 
issue.
Unfortunately, I dont have a N800 board with me to test it and will require
your help to do so.
-----------
From: Sourav Poddar <sourav.poddar@ti.com>
Date: Wed, 1 Aug 2012 15:44:12 +0530
Subject: [RFT/PATCH] serial: omap: Fix N800 serial init issue.


This patch might solve the N800 serial init issue.

This patch will also give pointers if there is any mux settings issue 
with N800 OR
a mismatch between the initial harware state, runtime PM state and omap 
hwmod state.

I don't have a N800 schematics to check about the mux settings getting used.

The observation on beagle board XM with this patch on different boards 
looks flaky,
so your feedback on beagle board will also be very helpful.

Cc: Felipe Balbi <balbi@ti.com>
Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
---
  drivers/tty/serial/omap-serial.c |    1 +
  1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c 
b/drivers/tty/serial/omap-serial.c
index 6ede6fd..3fbc7f7 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct 
platform_device *pdev)
         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);

         platform_set_drvdata(pdev, up);
+       pm_runtime_set_active(&pdev->dev);
         pm_runtime_enable(&pdev->dev);
         pm_runtime_use_autosuspend(&pdev->dev);
         pm_runtime_set_autosuspend_delay(&pdev->dev,
-- 
1.7.1

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Kevin Hilman]

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

> Hi Paul,
>
> There are
> On Thursday 11 October 2012 11:58 PM, Paul Walmsley wrote:
>> Hi Sourav, Felipe,
>>
>> any progress on fixing the N800 problem?  Would be good to keep it booting
>> since we use it as our primary 2420 test platform.
>>
>>
>> - Paul
> The patch sent inlined below might help us to get rid of the serial
> init issue.
> Unfortunately, I dont have a N800 board with me to test it and will require
> your help to do so.
> -----------
> From: Sourav Poddar <sourav.poddar@ti.com>
> Date: Wed, 1 Aug 2012 15:44:12 +0530
> Subject: [RFT/PATCH] serial: omap: Fix N800 serial init issue.
>
>
> This patch might solve the N800 serial init issue.
>
> This patch will also give pointers if there is any mux settings issue
> with N800 OR
> a mismatch between the initial harware state, runtime PM state and
> omap hwmod state.

> I don't have a N800 schematics to check about the mux settings getting used.
>
> The observation on beagle board XM with this patch on different boards
> looks flaky,
> so your feedback on beagle board will also be very helpful.
>
> Cc: Felipe Balbi <balbi@ti.com>
> Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
> ---
>  drivers/tty/serial/omap-serial.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/tty/serial/omap-serial.c
> b/drivers/tty/serial/omap-serial.c
> index 6ede6fd..3fbc7f7 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
> platform_device *pdev)
>         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
>
>         platform_set_drvdata(pdev, up);
> +       pm_runtime_set_active(&pdev->dev);

NAK.

This will obviously break platforms where the UARTs are not active
before driver loads.

Kevin

>         pm_runtime_enable(&pdev->dev);
>         pm_runtime_use_autosuspend(&pdev->dev);
>         pm_runtime_set_autosuspend_delay(&pdev->dev,

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
> Sourav <sourav.poddar@ti.com> writes:
> > diff --git a/drivers/tty/serial/omap-serial.c
> > b/drivers/tty/serial/omap-serial.c
> > index 6ede6fd..3fbc7f7 100644
> > --- a/drivers/tty/serial/omap-serial.c
> > +++ b/drivers/tty/serial/omap-serial.c
> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
> > platform_device *pdev)
> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
> >
> >         platform_set_drvdata(pdev, up);
> > +       pm_runtime_set_active(&pdev->dev);
> 
> NAK.
> 
> This will obviously break platforms where the UARTs are not active
> before driver loads.

I thought I had proposed a solution for this issue, which was this
sequence:

        omap_device_enable(dev);                                                
        pm_runtime_set_active(dev);                                             
        pm_runtime_enable(dev);                                                 

Yes, I can understand people not liking the omap_device_enable()
there, but I also notice that the email suggesting that never got a
reply either - not even a "I tried this and it doesn't work" or "it
does work".

As such, it seems this issue isn't making any progress as we had
already established that merely doing a "pm_runtime_set_active()"
before "pm_runtime_enable()" was going to break other platforms.

RE: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Poddar, Sourav]

Hi Russell,
________________________________________
From: Russell King - ARM Linux [linux@arm.linux.org.uk]
Sent: Friday, October 12, 2012 10:12 PM
To: Kevin Hilman
Cc: Poddar, Sourav; Paul Walmsley; Balbi, Felipe; gregkh@linuxfoundation.org; tony@atomide.com; linux-kernel@vger.kernel.org; Shilimkar, Santosh; linux-serial@vger.kernel.org; linux-omap@vger.kernel.org; linux-arm-kernel@lists.infradead.org; alan@linux.intel.com
Subject: Re: [RFT/PATCH] serial: omap: prevent resume if device is not  suspended.

On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
> Sourav <sourav.poddar@ti.com> writes:
> > diff --git a/drivers/tty/serial/omap-serial.c
> > b/drivers/tty/serial/omap-serial.c
> > index 6ede6fd..3fbc7f7 100644
> > --- a/drivers/tty/serial/omap-serial.c
> > +++ b/drivers/tty/serial/omap-serial.c
> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
> > platform_device *pdev)
> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
> >
> >         platform_set_drvdata(pdev, up);
> > +       pm_runtime_set_active(&pdev->dev);
>
> NAK.
>
> This will obviously break platforms where the UARTs are not active
> before driver loads.

I thought I had proposed a solution for this issue, which was this
sequence:

        omap_device_enable(dev);
        pm_runtime_set_active(dev);
        pm_runtime_enable(dev);

Yes, I can understand people not liking the omap_device_enable()
there, but I also notice that the email suggesting that never got a
reply either - not even a "I tried this and it doesn't work" or "it
does work".

Sorry for the late reply on this. I tried this sequence and it worked perfectly fine on
panda and beagle. 

As such, it seems this issue isn't making any progress as we had
already established that merely doing a "pm_runtime_set_active()"
before "pm_runtime_enable()" was going to break other platforms.

 I was  trying to analyse your explanations on this and since omap_device_enable is not generally 
recommended,  I was trying to see if anything else can be done to get around this.

I send this patch for N800 testing so  as to see how it behaves. (We are suspecting that there might be
mux setting issue also with N800).   

~Sourav

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Kevin Hilman]

Russell King - ARM Linux <linux@arm.linux.org.uk> writes:

> On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
>> Sourav <sourav.poddar@ti.com> writes:
>> > diff --git a/drivers/tty/serial/omap-serial.c
>> > b/drivers/tty/serial/omap-serial.c
>> > index 6ede6fd..3fbc7f7 100644
>> > --- a/drivers/tty/serial/omap-serial.c
>> > +++ b/drivers/tty/serial/omap-serial.c
>> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
>> > platform_device *pdev)
>> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
>> >
>> >         platform_set_drvdata(pdev, up);
>> > +       pm_runtime_set_active(&pdev->dev);
>> 
>> NAK.
>> 
>> This will obviously break platforms where the UARTs are not active
>> before driver loads.
>
> I thought I had proposed a solution for this issue, which was this
> sequence:
>
>         omap_device_enable(dev);                                                
>         pm_runtime_set_active(dev);                                             
>         pm_runtime_enable(dev);                                                 
>
> Yes, I can understand people not liking the omap_device_enable()
> there, but I also notice that the email suggesting that never got a
> reply either - not even a "I tried this and it doesn't work" or "it
> does work".

Yes, that solution would work (though I didn't actually try it.)

However, we can't use omap_device_enable() in the driver.  We're trying
to clean all the drivers of OMAP-specific APIs.  That being said,
something similar could be done in the device/board init code to ensure
the UART HW is in the state that the driver is expecting it, but again,
that would just mask the real problem which is that a (re)init of the
console UART on 2420/n800 is causing output to disappear.

As I detailed in an earlier response, I still think it's the fact that
the pinmux is not setup correctly for the console UART pins in the board
file, so when the UART is initialized, its mux settings are changed from
the bootloader defaults, causing output to disappear.

> As such, it seems this issue isn't making any progress as we had
> already established that merely doing a "pm_runtime_set_active()"
> before "pm_runtime_enable()" was going to break other platforms.

Agreed.

Kevin

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Fri, Oct 12, 2012 at 05:29:55PM +0000, Poddar, Sourav wrote:
> Hi Russell,
> ________________________________________
> From: Russell King - ARM Linux [linux@arm.linux.org.uk]
> Sent: Friday, October 12, 2012 10:12 PM
> To: Kevin Hilman
> Cc: Poddar, Sourav; Paul Walmsley; Balbi, Felipe; gregkh@linuxfoundation.org; tony@atomide.com; linux-kernel@vger.kernel.org; Shilimkar, Santosh; linux-serial@vger.kernel.org; linux-omap@vger.kernel.org; linux-arm-kernel@lists.infradead.org; alan@linux.intel.com
> Subject: Re: [RFT/PATCH] serial: omap: prevent resume if device is not  suspended.
> 
> On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
> > Sourav <sourav.poddar@ti.com> writes:
> > > diff --git a/drivers/tty/serial/omap-serial.c
> > > b/drivers/tty/serial/omap-serial.c
> > > index 6ede6fd..3fbc7f7 100644
> > > --- a/drivers/tty/serial/omap-serial.c
> > > +++ b/drivers/tty/serial/omap-serial.c
> > > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
> > > platform_device *pdev)
> > >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
> > >
> > >         platform_set_drvdata(pdev, up);
> > > +       pm_runtime_set_active(&pdev->dev);
> >
> > NAK.
> >
> > This will obviously break platforms where the UARTs are not active
> > before driver loads.
> 
> I thought I had proposed a solution for this issue, which was this
> sequence:
> 
>         omap_device_enable(dev);
>         pm_runtime_set_active(dev);
>         pm_runtime_enable(dev);
> 
> Yes, I can understand people not liking the omap_device_enable()
> there, but I also notice that the email suggesting that never got a
> reply either - not even a "I tried this and it doesn't work" or "it
> does work".
> 
> Sorry for the late reply on this. I tried this sequence and it worked perfectly fine on
> panda and beagle. 
> 
> As such, it seems this issue isn't making any progress as we had
> already established that merely doing a "pm_runtime_set_active()"
> before "pm_runtime_enable()" was going to break other platforms.
> 
>  I was  trying to analyse your explanations on this and since
> omap_device_enable is not generally recommended,  I was trying to see
> if anything else can be done to get around this.

Right, so what you need is explanation about why I believe the above
sequence to be necessary.

What is happening is that we're starting from a device in unknown state.
We don't know whether it is enabled or disabled.  We don't know the
state of the clocks or the power domain.

PM runtime state is initialized at device creation in the "device is
suspended" state.  If we merely enable PM runtime from that state, we
are telling the PM runtime subsystem that the device is _indeed_
suspended (disabled) at boot time.

So, that causes the first pm_runtime_get() call to resume the device.
Due to the OMAP runtime PM hooks at the bus layer, this causes
_od_runtime_resume() to be called.

_od_runtime_resume() does two things.  It calls omap_device_enable()
to ensure that the device is woken up (such as, ensuring that the
power domain is on, and turning on the clocks etc.)  It then goes on
to call the device PM layers to call the driver specific runtime PM
resume hook.

So, in summary, what this sequence does is:

        pm_runtime_enable(&pdev->dev);
        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_set_autosuspend_delay(&pdev->dev,
                        omap_up_info->autosuspend_timeout);

        pm_runtime_irq_safe(&pdev->dev);
        pm_runtime_get_sync(&pdev->dev);

is, at the last call, it calls:

		_od_runtime_resume()
			omap_device_enable()
			serial_omap_runtime_resume()

Your original patch at the head of this thread says that the driver
specific runtime resume call causes a problem for N800 - because the
device is already enabled and setup.

Okay, so the initial device state does not match the runtime PM state.

So, what happens if we _do_ make it match your state - as required by
the runtime PM documentation - by adding a call before the sequence:

	pm_runtime_set_active(&pdev->dev);
        pm_runtime_enable(&pdev->dev);
        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_set_autosuspend_delay(&pdev->dev,
                        omap_up_info->autosuspend_timeout);

        pm_runtime_irq_safe(&pdev->dev);
        pm_runtime_get_sync(&pdev->dev);

Right, now runtime PM knows that the device is enabled and alive prior
to that pm_runtime_get_sync() call, and it will _not_ call the runtime
resume hooks.

However, this breaks beaglebone, because the device is disabled when
this driver probes.  So, we have exactly the opposite problem here -
the device is disabled, but runtime PM thinks it is enabled.

The _two_ problems are precisely the same problem: the runtime PM state
does not accurately reflect the actual hardware state - again, as required
by the runtime PM documentation.  The only sane solution to this is to
ensure that the hardware _is_ in a known state prior to enabling runtime
PM.

How do we do that?  Well, the clue is in the bus layer runtime resume
handler - that's what is missing from the beaglebone situation.

Calling this before calling pm_runtime_set_active() gets the hardware
into a known state (enabled), and we then tell the runtime PM code
that the harware _is_ enabled.  Now, runtime PM can be sure what the
initial state is, and everything works.

What's the longer term answer?

Well, I _bet_ all OMAP drivers are doing something along the lines of:

	pm_runtime_enable(dev);
	pm_runtime_get(dev);

in their probe functions.

PCI already solved this problem - partly because it has far too many drivers
to convert.  I took that solution over to the AMBA bus layer, because I
didn't want to have a flag day for all the drivers to convert over in one
massive patch.  What is this solution?

You get the bus layer to handle the initial setup of runtime PM state like
this - in OMAP's case:

	omap_device_enable(pdev);
	pm_runtime_get_noresume(&pdev->dev);
	pm_runtime_set_active(&pdev->dev);
	pm_runtime_enable(&pdev->dev);

You do this prior to calling the device probe function.  If the device
probe fails, then you can undo those actions.  You also need to undo them
when the device is unbound from the driver:

	pm_runtime_disable(&pdev->dev);
	pm_runtime_set_suspended(&pdev->dev);
	pm_runtime_put_noidle(&pdev->dev);

(It is probably dangerous to call omap_device_disable() here for certain
devices...)

This gets rid of all that driver specific runtime PM initialization, with
questionable starting state.  It also means that your devices all get
runtime PM support in so far as if they're bound to a driver, they will
be runtime PM resumed, and when unbound, they will be runtime PM suspended.

However, it means that the driver has to do something to make runtime PM
work.  In the probe function, just before it returns success, it has to
'put' that pm_runtime_get_noresume() reference to allow the device to
enter runtime PM states.  And more importantly, on a remove call, it
_must_ balance that 'put' in the probe with an appropriate 'get' - no
exceptions to that.

And that is how we get to a sane state over runtime PM here, which will
work in every situation on every device, without throwing calls to
omap_device_enable() into every OMAP device driver.

This also has another advantage - by doing that, the OMAP specific
omap_device_enable() call ends up being in bus layer code, not driver
layer, which is the right place for it to be - after all, it's the
bus layer which is already handling that stuff in its runtime PM support
code.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Russell King - ARM Linux]

On Fri, Oct 12, 2012 at 10:59:22AM -0700, Kevin Hilman wrote:
> Russell King - ARM Linux <linux@arm.linux.org.uk> writes:
> 
> > On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
> >> Sourav <sourav.poddar@ti.com> writes:
> >> > diff --git a/drivers/tty/serial/omap-serial.c
> >> > b/drivers/tty/serial/omap-serial.c
> >> > index 6ede6fd..3fbc7f7 100644
> >> > --- a/drivers/tty/serial/omap-serial.c
> >> > +++ b/drivers/tty/serial/omap-serial.c
> >> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
> >> > platform_device *pdev)
> >> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
> >> >
> >> >         platform_set_drvdata(pdev, up);
> >> > +       pm_runtime_set_active(&pdev->dev);
> >> 
> >> NAK.
> >> 
> >> This will obviously break platforms where the UARTs are not active
> >> before driver loads.
> >
> > I thought I had proposed a solution for this issue, which was this
> > sequence:
> >
> >         omap_device_enable(dev);                                                
> >         pm_runtime_set_active(dev);                                             
> >         pm_runtime_enable(dev);                                                 
> >
> > Yes, I can understand people not liking the omap_device_enable()
> > there, but I also notice that the email suggesting that never got a
> > reply either - not even a "I tried this and it doesn't work" or "it
> > does work".
> 
> Yes, that solution would work (though I didn't actually try it.)
> 
> However, we can't use omap_device_enable() in the driver.  We're trying
> to clean all the drivers of OMAP-specific APIs.  That being said,
> something similar could be done in the device/board init code to ensure
> the UART HW is in the state that the driver is expecting it, but again,
> that would just mask the real problem which is that a (re)init of the
> console UART on 2420/n800 is causing output to disappear.

See my more expansive suggestion just posted.

Whatever way, this discrepancy between runtime PM state and actual device
state is what is biting you, and it is that which needs fixing.  It's
fairly easy to fix given the right design, one which several other bus
types are already using.

Given the route that OMAP went down when adopting runtime PM, it's going
to be a big change across many drivers, because there's no way to gradually
transition them, but that's unfortunately one of the results of ignoring
requirements of the layers being used.  Sooner or later the oversights
come back to haunt.  Just make sure it's not the ghost of Jaws.

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Kevin Hilman]

Russell King - ARM Linux <linux@arm.linux.org.uk> writes:

> On Fri, Oct 12, 2012 at 10:59:22AM -0700, Kevin Hilman wrote:
>> Russell King - ARM Linux <linux@arm.linux.org.uk> writes:
>> 
>> > On Fri, Oct 12, 2012 at 09:35:54AM -0700, Kevin Hilman wrote:
>> >> Sourav <sourav.poddar@ti.com> writes:
>> >> > diff --git a/drivers/tty/serial/omap-serial.c
>> >> > b/drivers/tty/serial/omap-serial.c
>> >> > index 6ede6fd..3fbc7f7 100644
>> >> > --- a/drivers/tty/serial/omap-serial.c
>> >> > +++ b/drivers/tty/serial/omap-serial.c
>> >> > @@ -1414,6 +1414,7 @@ static int __devinit serial_omap_probe(struct
>> >> > platform_device *pdev)
>> >> >         INIT_WORK(&up->qos_work, serial_omap_uart_qos_work);
>> >> >
>> >> >         platform_set_drvdata(pdev, up);
>> >> > +       pm_runtime_set_active(&pdev->dev);
>> >> 
>> >> NAK.
>> >> 
>> >> This will obviously break platforms where the UARTs are not active
>> >> before driver loads.
>> >
>> > I thought I had proposed a solution for this issue, which was this
>> > sequence:
>> >
>> >         omap_device_enable(dev);                                                
>> >         pm_runtime_set_active(dev);                                             
>> >         pm_runtime_enable(dev);                                                 
>> >
>> > Yes, I can understand people not liking the omap_device_enable()
>> > there, but I also notice that the email suggesting that never got a
>> > reply either - not even a "I tried this and it doesn't work" or "it
>> > does work".
>> 
>> Yes, that solution would work (though I didn't actually try it.)
>> 
>> However, we can't use omap_device_enable() in the driver.  We're trying
>> to clean all the drivers of OMAP-specific APIs.  That being said,
>> something similar could be done in the device/board init code to ensure
>> the UART HW is in the state that the driver is expecting it, but again,
>> that would just mask the real problem which is that a (re)init of the
>> console UART on 2420/n800 is causing output to disappear.
>
> See my more expansive suggestion just posted.
>
> Whatever way, this discrepancy between runtime PM state and actual device
> state is what is biting you, and it is that which needs fixing.  

I'm not conviced (yet) that a mismatch is the root cause.  Yes, that's
what the author of $SUBJECT patch assumed and stated, but I'm not
pursuaded.  

If it's an improperly configured mux issue, then the UART will break
whenever the device is actually omap_device_enable'd, whether in the
driver or in the bus layer.

Kevin

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Tony Lindgren]

* Kevin Hilman <khilman@deeprootsystems.com> [121012 13:34]:
>
> I'm not conviced (yet) that a mismatch is the root cause.  Yes, that's
> what the author of $SUBJECT patch assumed and stated, but I'm not
> pursuaded.  
> 
> If it's an improperly configured mux issue, then the UART will break
> whenever the device is actually omap_device_enable'd, whether in the
> driver or in the bus layer.

I tried booting n800 here with CONFIG_OMAP_MUX disabled, and no
change. Serial console output stops right when the console initializes.

Regards,

Tony

Re: [RFT/PATCH] serial: omap: prevent resume if device is not suspended.

[Kevin Hilman]

Tony Lindgren <tony@atomide.com> writes:

> * Kevin Hilman <khilman@deeprootsystems.com> [121012 13:34]:
>>
>> I'm not conviced (yet) that a mismatch is the root cause.  Yes, that's
>> what the author of $SUBJECT patch assumed and stated, but I'm not
>> pursuaded.  
>> 
>> If it's an improperly configured mux issue, then the UART will break
>> whenever the device is actually omap_device_enable'd, whether in the
>> driver or in the bus layer.
>
> I tried booting n800 here with CONFIG_OMAP_MUX disabled, and no
> change. Serial console output stops right when the console initializes.

OK, since it's not mux, and since those who actually maintain this
driver don't seem to be taking care of this, I did some digging today.

Russell is right.  It's a mismatch between assumed runtime PM state
(disabled) and actual HW state.

During init, all omap_devices are idled by default, so that they are
correctly in the state that the runtime PM framework will later expect
them to be.  That is, all devices *except* the console UART.  For that
one, we use the special hwmod flag to not idle/reset the UART since that
will cause problems during earlyprintk usage, and the switch between
the earlyprintk console and the real console driver.

Since the console uart was left enabled during init, it needs to be
fully enabled and the runtime PM status set accordingly.

The patch below does this, and works fine on 2420/n810, as well as on
3530/Overo, 3730/OveroSTORM, 3730/Beagle-XM and 4430/PandaES.

Will send patch with a proper changelog shortly,

Kevin

diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
index 0405c81..37b5dbe 100644
--- a/arch/arm/mach-omap2/serial.c
+++ b/arch/arm/mach-omap2/serial.c
@@ -327,6 +327,11 @@ void __init omap_serial_init_port(struct omap_board_data *bdata,
 	if ((console_uart_id == bdata->id) && no_console_suspend)
 		omap_device_disable_idle_on_suspend(pdev);
 
+	if (console_uart_id == bdata->id) {
+		omap_device_enable(pdev);
+		pm_runtime_set_active(&pdev->dev);
+	}
+
 	oh->mux = omap_hwmod_mux_init(bdata->pads, bdata->pads_cnt);
 
 	oh->dev_attr = uart;