linux-kernel - Re: [PATCHv3 6/8] serial: imx: add runtime pm support

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Date:	Fri, 14 Aug 2015 18:20:35 -0700
From:	Eduardo Valentin <edubezval@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.com>, Fabio Estevam <festevam@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Linux PM <linux-pm@...r.kernel.org>,
	linux-serial@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv3 6/8] serial: imx: add runtime pm support

On Fri, Aug 14, 2015 at 05:23:12PM -0700, Greg Kroah-Hartman wrote:
> On Tue, Aug 11, 2015 at 10:21:25AM -0700, Eduardo Valentin wrote:
> > This change introduces the runtime pm support on imx serial
> > driver. The objective is to be able to idle the uart
> > port whenever it is not in use while still being able
> > to wake it up when needed. The key changes in this patch are:
> > 1. Move the clock handling to runtime pm. Both, ipg and per,
> > are now handled in the suspend and resume callbacks. Only
> > enabling and disabling the clocks are handled in runtime
> > suspend and resume, so we are able to use runtime pm
> > in IRQ context.
> > 2. Clocks are prepared in probe and unprepared in remove,
> > so we do not need to prepare (may sleep) in runtime pm.
> > 3. We mark the device activity based on uart and console
> > callbacks. Whenever the device is needed and we want to
> > access registers, we runtime_pm_get and then mark its
> > last usage when we are done. This is done also across
> > IRQs and DMA callbacks.
> > 4. We reuse the infrastructure in place for suspend and
> > resume, so we do not need to redo wakeup configuration,
> > or context save and restore.
> > 
> > After this change, the clocks are still sane, in the sense
> > of having balanced clock prepare and enable.
> > 
> > Cc: Fabio Estevam <festevam@...il.com>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Jiri Slaby <jslaby@...e.com>
> > Cc: linux-serial@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Signed-off-by: Eduardo Valentin <edubezval@...il.com>
> > ---
> >  drivers/tty/serial/imx.c | 224 +++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 178 insertions(+), 46 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> > index 50abb60..9447a55 100644
> > --- a/drivers/tty/serial/imx.c
> > +++ b/drivers/tty/serial/imx.c
> > @@ -39,6 +39,9 @@
> >  #include <linux/of_device.h>
> >  #include <linux/io.h>
> >  #include <linux/dma-mapping.h>
> > +#include <linux/pm.h>
> > +#include <linux/pm_runtime.h>
> > +#include <linux/pm_wakeup.h>
> >  
> >  #include <asm/irq.h>
> >  #include <linux/platform_data/serial-imx.h>
> > @@ -219,6 +222,7 @@ struct imx_port {
> >  	unsigned int            saved_reg[10];
> >  	bool			context_saved;
> >  
> > +	struct device		*dev;
> 
> Do you really need this pointer?  Can't you get it from the platform
> device that you have access to that sport is the data?

Actually, not really. I can change the code to the one in sport. I will
be resending soon.

> 
> thanks,
> 
> greg k-h

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