RE: [PATCH 3/3] fpga: region: Adds runtime PM support

[Nava kishore Manne <navam@xxxxxxxxxx>]

Ping!

> -----Original Message-----
> From: Nava kishore Manne
> Sent: Monday, April 19, 2021 10:49 AM
> To: Moritz Fischer <mdf@xxxxxxxxxx>
> Cc: trix@xxxxxxxxxx; robh+dt@xxxxxxxxxx; Michal Simek
> <michals@xxxxxxxxxx>; linux-fpga@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> Subject: RE: [PATCH 3/3] fpga: region: Adds runtime PM support
> 
> Hi Moritz,
> 
> 	Please find my response inline.
> 
> > -----Original Message-----
> > From: Moritz Fischer <mdf@xxxxxxxxxx>
> > Sent: Saturday, April 10, 2021 3:01 AM
> > To: Nava kishore Manne <navam@xxxxxxxxxx>
> > Cc: mdf@xxxxxxxxxx; trix@xxxxxxxxxx; robh+dt@xxxxxxxxxx; Michal Simek
> > <michals@xxxxxxxxxx>; linux-fpga@xxxxxxxxxxxxxxx;
> > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> > kernel@xxxxxxxxxxxxxxxxxxx; git <git@xxxxxxxxxx>
> > Subject: Re: [PATCH 3/3] fpga: region: Adds runtime PM support
> >
> > On Fri, Apr 02, 2021 at 02:50:49PM +0530, Nava kishore Manne wrote:
> > > Adds support to handle FPGA/PL power domain. With this patch, the PL
> > > power domain will be turned on before loading the bitstream and
> > > turned off while removing/unloading the bitstream using overlays.
> > > This can be achieved by adding the runtime PM support.
> > >
> > > Signed-off-by: Nava kishore Manne <nava.manne@xxxxxxxxxx>
> > > ---
> > >  drivers/fpga/of-fpga-region.c | 18 +++++++++++++++++-
> > >  1 file changed, 17 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/fpga/of-fpga-region.c
> > > b/drivers/fpga/of-fpga-region.c index e405309baadc..35fc2f3d4bd8
> > > 100644
> > > --- a/drivers/fpga/of-fpga-region.c
> > > +++ b/drivers/fpga/of-fpga-region.c
> > > @@ -15,6 +15,7 @@
> > >  #include <linux/of_platform.h>
> > >  #include <linux/slab.h>
> > >  #include <linux/spinlock.h>
> > > +#include <linux/pm_runtime.h>
> > >
> > >  static const struct of_device_id fpga_region_of_match[] = {
> > >  	{ .compatible = "fpga-region", },
> > > @@ -302,6 +303,7 @@ static int
> > > of_fpga_region_notify_pre_apply(struct
> > fpga_region *region,
> > >  	}
> > >
> > >  	region->info = info;
> > > +	pm_runtime_get_sync(dev->parent);
> > >  	ret = fpga_region_program_fpga(region);
> > >  	if (ret) {
> > >  		/* error; reject overlay */
> > > @@ -324,10 +326,13 @@ static int
> > > of_fpga_region_notify_pre_apply(struct fpga_region *region,  static
> > > void
> > of_fpga_region_notify_post_remove(struct fpga_region *region,
> > >  					      struct of_overlay_notify_data
> > *nd)  {
> > > +	struct device *dev = &region->dev;
> > > +
> > >  	fpga_bridges_disable(&region->bridge_list);
> > >  	fpga_bridges_put(&region->bridge_list);
> > >  	fpga_image_info_free(region->info);
> > >  	region->info = NULL;
> > > +	pm_runtime_put(dev->parent);
> > >  }
> > >
> > >  /**
> > > @@ -411,9 +416,16 @@ static int of_fpga_region_probe(struct
> > platform_device *pdev)
> > >  		goto eprobe_mgr_put;
> > >  	}
> > >
> > > +	pm_runtime_enable(&pdev->dev);
> > > +	ret = pm_runtime_get_sync(&pdev->dev);
> > > +	if (ret < 0)
> > > +		goto err_pm;
> > > +
> > > +	pm_runtime_put(&pdev->dev);
> > > +
> > >  	ret = fpga_region_register(region);
> > >  	if (ret)
> > > -		goto eprobe_mgr_put;
> > > +		goto err_pm;
> > >
> > >  	of_platform_populate(np, fpga_region_of_match, NULL, &region-
> > >dev);
> > >  	platform_set_drvdata(pdev, region);  @@ -422,6 +434,9 @@ static
> > >int of_fpga_region_probe(struct  platform_device *pdev)
> > >
> > >  	return 0;
> > >
> > > +err_pm:
> > > +	pm_runtime_put(&pdev->dev);
> > > +	pm_runtime_disable(&pdev->dev);
> > >  eprobe_mgr_put:
> > >  	fpga_mgr_put(mgr);
> > >  	return ret;
> > > @@ -434,6 +449,7 @@ static int of_fpga_region_remove(struct
> > > platform_device *pdev)
> > >
> > >  	fpga_region_unregister(region);
> > >  	fpga_mgr_put(mgr);
> > > +	pm_runtime_disable(region->dev.parent);
> > >
> > >  	return 0;
> > >  }
> > > --
> > > 2.18.0
> > >
> >
> > Does this add a dependency on CONFIG_PM?
> >
> Yes, the newly added functionality has a dependency on CONFIG_PM if it's
> disabled the expected power domain (in our cases it's PL) will not powered
> ON/OFF dynamically at runtime and this is as an expected behavior. Other
> than this it will not impact the any of the driver existing functionality.
> 
> Regards,
> Navakishore.