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

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On 6/2/21 3:48 AM, Nava kishore Manne wrote:
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.

This looks like a general change for a specific board.

Why can't this be done at the board level ?

Tom


Regards,
Navakishore.




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