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

[Nava kishore Manne]

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.