Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Wolfram Sang]

Morimoto-san,

> > +   pm_runtime_enable(dev);
> > +   pm_runtime_get_sync(dev);
> > rcar_i2c_init(priv);
> > +   pm_runtime_put(dev);
> 
> Please correct me if I'm misunderstanding, but in my experience,
> above rcar_i2c_init() result can be removed if SoC has power-off feature,
> and if IP doesn't keep register value power-off case ?
> This case register doesn't keep myfunc_A's setting,
> because it calls pm_runtime_put()
> 
>  pm_runtime_get_sync()
>  myfunc_A()
>  pm_runtime_put()
>  ...
>  pm_runtime_get_sync()
>  myfunc_B()
>  pm_runtime_put()
> 
> It should be this ?
> 
>  pm_runtime_get_sync()
>  myfunc_A()
>  myfunc_B()
>  pm_runtime_put()

This is for power-off case, right? Wouldn't it be clearer then to add a
resume function to pm_ops of the I2C driver which reinit the registers?
Doing it before every transfer might be simpler but is also a bit
implicit or subtle, I'd think.

And for completeness: The above is only for the power-off case. In
module-standby (MSTP bits), register values are always retained.
Correct?

Regards,

   Wolfram



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Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Kuninori Morimoto]

Hi Wolfram

> >  pm_runtime_get_sync()
> >  myfunc_A()
> >  pm_runtime_put()
> >  ...
> >  pm_runtime_get_sync()
> >  myfunc_B()
> >  pm_runtime_put()
> > 
> > It should be this ?
> > 
> >  pm_runtime_get_sync()
> >  myfunc_A()
> >  myfunc_B()
> >  pm_runtime_put()
> 
> This is for power-off case, right? Wouldn't it be clearer then to add a
> resume function to pm_ops of the I2C driver which reinit the registers?
> Doing it before every transfer might be simpler but is also a bit
> implicit or subtle, I'd think.
> 
> And for completeness: The above is only for the power-off case. In
> module-standby (MSTP bits), register values are always retained.
> Correct?

I'm not sure detail of pm_runtime, but it depends on
power-domain support ?
On SH-Mobile case, it automatically power-off:ed if all driver
user was gone. This feature is not yet supported on R-Car case I think.
So, both case are not problem at this point, but 1st case will be
problem if power-domain was suppored.
(If my memory was correct...)
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Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Wolfram Sang]

> On SH-Mobile case, it automatically power-off:ed if all driver
> user was gone.

It does that without calling some callback?



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Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Kuninori Morimoto]

Hi Wolfram

> > On SH-Mobile case, it automatically power-off:ed if all driver
> > user was gone.
> 
> It does that without calling some callback?

Do you mean you can call init() in callback ?
I don't care detail of design. But my concern was that
register value might be disappear during many get/put if
power-domain was implemented

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Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Geert Uytterhoeven]

Hi Wolfram,

On Thu, Oct 29, 2015 at 8:19 PM, Wolfram Sang  wrote:
> From: Wolfram Sang 
>
> Reported-by: Kuninori Morimoto 
> Signed-off-by: Wolfram Sang 

Thanks for your patch!

I suspect this bug was also the cause of the spurious failures of the R-Car
Gen2 regulator quirk code I experienced sometimes during the last few
days.

> ---
>  drivers/i2c/busses/i2c-rcar.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
> index 616433d387cdb2..ef26e933b1e9cb 100644
> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -612,7 +612,10 @@ static int rcar_i2c_probe(struct platform_device *pdev)
> if (IS_ERR(priv->io))
> return PTR_ERR(priv->io);
>
> +   pm_runtime_enable(dev);
> +   pm_runtime_get_sync(dev);
> rcar_i2c_init(priv);
> +   pm_runtime_put(dev);
>
> irq = platform_get_irq(pdev, 0);
> init_waitqueue_head(>wait);
> @@ -634,7 +637,6 @@ static int rcar_i2c_probe(struct platform_device *pdev)
> return ret;

pm_runtime_disable() in error path?

> }

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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Re: [PATCH] i2c: rcar: make sure clocks are on when doing hw init

[Kuninori Morimoto]

Hi, Wolfram

> From: Wolfram Sang 
> 
> Reported-by: Kuninori Morimoto 
> Signed-off-by: Wolfram Sang 
> ---
>  drivers/i2c/busses/i2c-rcar.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
> index 616433d387cdb2..ef26e933b1e9cb 100644
> --- a/drivers/i2c/busses/i2c-rcar.c
> +++ b/drivers/i2c/busses/i2c-rcar.c
> @@ -612,7 +612,10 @@ static int rcar_i2c_probe(struct platform_device *pdev)
>   if (IS_ERR(priv->io))
>   return PTR_ERR(priv->io);
>  
> + pm_runtime_enable(dev);
> + pm_runtime_get_sync(dev);
>   rcar_i2c_init(priv);
> + pm_runtime_put(dev);

Please correct me if I'm misunderstanding, but in my experience,
above rcar_i2c_init() result can be removed if SoC has power-off feature,
and if IP doesn't keep register value power-off case ?
This case register doesn't keep myfunc_A's setting,
because it calls pm_runtime_put()

 pm_runtime_get_sync()
 myfunc_A()
 pm_runtime_put()
 ...
 pm_runtime_get_sync()
 myfunc_B()
 pm_runtime_put()

It should be this ?

 pm_runtime_get_sync()
 myfunc_A()
 myfunc_B()
 pm_runtime_put()
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