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

Tom Rix
2021-06-02T20:39:18Z

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@kernel.org>
>> Cc: trix@redhat.com; robh+dt@kernel.org; Michal Simek
>> <michals@xilinx.com>; linux-fpga@vger.kernel.org;
>> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-
>> kernel@lists.infradead.org; git <git@xilinx.com>
>> Subject: RE: [PATCH 3/3] fpga: region: Adds runtime PM support
>>
>> Hi Moritz,
>>
>> Please find my response inline.
>>
>>> -----Original Message-----
>>> From: Moritz Fischer <mdf@kernel.org>
>>> Sent: Saturday, April 10, 2021 3:01 AM
>>> To: Nava kishore Manne <navam@xilinx.com>
>>> Cc: mdf@kernel.org; trix@redhat.com; robh+dt@kernel.org; Michal Simek
>>> <michals@xilinx.com>; linux-fpga@vger.kernel.org;
>>> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-
>>> kernel@lists.infradead.org; git <git@xilinx.com>
>>> 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@xilinx.com>
>>>> ---
>>>> 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.