Message-ID: <Z0fIiQPCS69O2d/n@yilunxu-OptiPlex-7050>
Date: Thu, 28 Nov 2024 09:34:01 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: Marco Pagani <marpagan@...hat.com>
Cc: Nava kishore Manne <nava.kishore.manne@....com>, git@....com,
	mdf@...nel.org, hao.wu@...el.com, yilun.xu@...el.com,
	trix@...hat.com, robh@...nel.org, saravanak@...gle.com,
	linux-kernel@...r.kernel.org, linux-fpga@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [RFC v2 1/1] fpga-region: Add generic IOCTL interface for
 runtime FPGA programming

On Mon, Nov 25, 2024 at 12:26:06PM +0100, Marco Pagani wrote:
> 
> 
> On 2024-11-19 05:14, Xu Yilun wrote:
> > On Tue, Oct 29, 2024 at 02:47:34PM +0530, Nava kishore Manne wrote:
> >> Introduces an IOCTL interface within the fpga-region subsystem,
> >> providing a generic and standardized mechanism for configuring (or)
> >> reprogramming FPGAs during runtime. The newly added interface supports
> >> both OF (Open Firmware) and non-OF devices, leveraging vendor-specific
> >> callbacks (e.g., configuration + enumeration, removal, and status) to
> >> accommodate a wide range of device specific configurations.
> >>
> >> The IOCTL interface ensures compatibility with both OF and non-OF
> >> devices, allowing for seamless FPGA reprogramming across diverse
> >> platforms.
> >>
> >> Vendor-specific callbacks are integrated into the interface, enabling
> >> custom FPGA configuration + enumeration, removal, and status reporting
> >> mechanisms, ensuring flexibility for vendor implementations.
> >>
> >> This solution enhances FPGA runtime management, supporting various device
> >> types and vendors, while ensuring compatibility with the current FPGA
> >> configuration flow.
> >>
> >> Signed-off-by: Nava kishore Manne <nava.kishore.manne@....com>
> >> ---
> >> Changes for v2:
> >>  - As discussed with Yilun, the implementation has been modified to utilize a
> >>  callback approach, enabling seamless handling of both OF and non-OF devices.
> >>
> >>  - As suggested by Yilun in the POC code, we have moved away from using  void *args
> >>  as a parameter for ICOTL inputs to obtain the required user inputs. Instead, we are
> >>  utilizing the fpga_region_config_info structure to gather user inputs. Currently,
> >>  this structure is implemented to support only OF devices, but we intend to extend
> >>  it by incorporating new members to accommodate non-OF devices in the future.
> >>
> >>  drivers/fpga/fpga-region.c       | 110 +++++++++++++++++++++++++++++++
> >>  drivers/fpga/of-fpga-region.c    |  91 ++++++++++++++++++++++++-
> >>  include/linux/fpga/fpga-region.h |  32 +++++++++
> >>  include/uapi/linux/fpga-region.h |  51 ++++++++++++++
> >>  4 files changed, 283 insertions(+), 1 deletion(-)
> >>  create mode 100644 include/uapi/linux/fpga-region.h
> >>
> >> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> >> index 753cd142503e..c6bea3c99a69 100644
> >> --- a/drivers/fpga/fpga-region.c
> >> +++ b/drivers/fpga/fpga-region.c
> >> @@ -8,6 +8,7 @@
> >>  #include <linux/fpga/fpga-bridge.h>
> >>  #include <linux/fpga/fpga-mgr.h>
> >>  #include <linux/fpga/fpga-region.h>
> >> +#include <linux/fpga-region.h>
> >>  #include <linux/idr.h>
> >>  #include <linux/kernel.h>
> >>  #include <linux/list.h>
> >> @@ -180,6 +181,67 @@ static struct attribute *fpga_region_attrs[] = {
> >>  };
> >>  ATTRIBUTE_GROUPS(fpga_region);
> >>  
> >> +static int fpga_region_device_open(struct inode *inode, struct file *file)
> >> +{
> >> +	struct miscdevice *miscdev = file->private_data;
> >> +	struct fpga_region *region = container_of(miscdev, struct fpga_region, miscdev);
> >> +
> >> +	file->private_data = region;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static int fpga_region_device_release(struct inode *inode, struct file *file)
> >> +{
> >> +	return 0;
> >> +}
> >> +
> >> +static long fpga_region_device_ioctl(struct file *file, unsigned int cmd,
> >> +				     unsigned long arg)
> >> +{
> >> +	int err;
> >> +	void __user *argp = (void __user *)arg;
> >> +	struct fpga_region_config_info config_info;
> >> +	struct fpga_region *region =  (struct fpga_region *)(file->private_data);
> >> +
> >> +	switch (cmd) {
> >> +	case FPGA_REGION_IOCTL_LOAD:
> >> +		if (copy_from_user(&config_info, argp, sizeof(struct fpga_region_config_info)))
> >> +			return -EFAULT;
> >> +
> >> +		err = region->region_ops->region_config_enumeration(region, &config_info);
> >> +
> >> +		break;
> >> +	case FPGA_REGION_IOCTL_REMOVE:
> >> +		if (copy_from_user(&config_info, argp, sizeof(struct fpga_region_config_info)))
> >> +			return -EFAULT;
> >> +
> >> +		err = region->region_ops->region_remove(region, &config_info);
> >> +
> >> +		break;
> >> +	case FPGA_REGION_IOCTL_STATUS:
> >> +		unsigned int status;
> >> +
> >> +		status = region->region_ops->region_status(region);
> >> +
> >> +		if (copy_to_user((void __user *)arg, &status, sizeof(status)))
> >> +			err = -EFAULT;
> >> +		break;
> >> +	default:
> >> +		err = -ENOTTY;
> >> +	}
> >> +
> >> +	return err;
> >> +}
> >> +
> >> +static const struct file_operations fpga_region_fops = {
> >> +	.owner		= THIS_MODULE,
> >> +	.open		= fpga_region_device_open,
> >> +	.release	= fpga_region_device_release,
> >> +	.unlocked_ioctl	= fpga_region_device_ioctl,
> >> +	.compat_ioctl	= fpga_region_device_ioctl,
> >> +};
> >> +
> >>  /**
> >>   * __fpga_region_register_full - create and register an FPGA Region device
> >>   * @parent: device parent
> >> @@ -229,8 +291,21 @@ __fpga_region_register_full(struct device *parent, const struct fpga_region_info
> >>  	if (ret)
> >>  		goto err_remove;
> >>  
> >> +	if (info->region_ops) {
> >> +		region->region_ops = info->region_ops;
> >> +		region->miscdev.minor = MISC_DYNAMIC_MINOR;
> >> +		region->miscdev.name = kobject_name(&region->dev.kobj);
> >> +		region->miscdev.fops = &fpga_region_fops;
> >> +		ret = misc_register(&region->miscdev);
> >> +		if (ret) {
> >> +			pr_err("fpga-region: failed to register misc device.\n");
> >> +			goto err_remove;
> >> +		}
> >> +	}
> >> +
> >>  	ret = device_register(&region->dev);
> >>  	if (ret) {
> >> +		misc_deregister(&region->miscdev);
> >>  		put_device(&region->dev);
> >>  		return ERR_PTR(ret);
> >>  	}
> >> @@ -272,6 +347,40 @@ __fpga_region_register(struct device *parent, struct fpga_manager *mgr,
> >>  }
> >>  EXPORT_SYMBOL_GPL(__fpga_region_register);
> >>  
> >> +/**
> >> + * __fpga_region_register_with_ops - create and register an FPGA Region device
> >> + * with user interface call-backs.
> >> + * @parent: device parent
> >> + * @mgr: manager that programs this region
> >> + * @region_ops: ops for low level FPGA region for device enumeration/removal
> >> + * @priv: of-fpga-region private data
> >> + * @get_bridges: optional function to get bridges to a list
> >> + * @owner: module containing the get_bridges function
> >> + *
> >> + * This simple version of the register function should be sufficient for most users.
> >> + * The fpga_region_register_full() function is available for users that need to
> >> + * pass additional, optional parameters.
> >> + *
> >> + * Return: struct fpga_region or ERR_PTR()
> >> + */
> >> +struct fpga_region *
> >> +__fpga_region_register_with_ops(struct device *parent, struct fpga_manager *mgr,
> >> +				const struct fpga_region_ops *region_ops,
> >> +				void *priv,
> >> +				int (*get_bridges)(struct fpga_region *),
> >> +				struct module *owner)
> >> +{
> >> +	struct fpga_region_info info = { 0 };
> >> +
> >> +	info.mgr = mgr;
> >> +	info.priv = priv;
> >> +	info.get_bridges = get_bridges;
> >> +	info.region_ops = region_ops;
> >> +
> >> +	return __fpga_region_register_full(parent, &info, owner);
> >> +}
> >> +EXPORT_SYMBOL_GPL(__fpga_region_register_with_ops);
> >> +
> >>  /**
> >>   * fpga_region_unregister - unregister an FPGA region
> >>   * @region: FPGA region
> >> @@ -280,6 +389,7 @@ EXPORT_SYMBOL_GPL(__fpga_region_register);
> >>   */
> >>  void fpga_region_unregister(struct fpga_region *region)
> >>  {
> >> +	misc_deregister(&region->miscdev);
> >>  	device_unregister(&region->dev);
> >>  }
> >>  EXPORT_SYMBOL_GPL(fpga_region_unregister);
> >> diff --git a/drivers/fpga/of-fpga-region.c b/drivers/fpga/of-fpga-region.c
> >> index 8526a5a86f0c..63fe56e0466f 100644
> >> --- a/drivers/fpga/of-fpga-region.c
> >> +++ b/drivers/fpga/of-fpga-region.c
> >> @@ -8,6 +8,8 @@
> >>  #include <linux/fpga/fpga-bridge.h>
> >>  #include <linux/fpga/fpga-mgr.h>
> >>  #include <linux/fpga/fpga-region.h>
> >> +#include <linux/firmware.h>
> >> +#include <linux/fpga-region.h>
> >>  #include <linux/idr.h>
> >>  #include <linux/kernel.h>
> >>  #include <linux/list.h>
> >> @@ -18,6 +20,20 @@
> >>  #include <linux/slab.h>
> >>  #include <linux/spinlock.h>
> >>  
> >> +/**
> >> + * struct of_fpga_region_priv - Private data structure
> >> + * image.
> >> + * @dev:	Device data structure
> >> + * @fw:		firmware of coeff table.
> >> + * @path:	path of FPGA overlay image firmware file.
> >> + * @ovcs_id:	overlay changeset id.
> >> + */
> >> +struct of_fpga_region_priv {
> >> +	struct device *dev;
> >> +	const struct firmware *fw;
> >> +	int ovcs_id;
> >> +};
> >> +
> >>  static const struct of_device_id fpga_region_of_match[] = {
> >>  	{ .compatible = "fpga-region", },
> >>  	{},
> >> @@ -394,20 +410,93 @@ static struct notifier_block fpga_region_of_nb = {
> >>  	.notifier_call = of_fpga_region_notify,
> >>  };
> >>  
> >> +static int of_fpga_region_status(struct fpga_region *region)
> >> +{
> >> +	struct of_fpga_region_priv *ovcs = region->priv;
> >> +
> >> +	if (ovcs->ovcs_id)
> >> +		return FPGA_REGION_HAS_PL;
> > 
> > Could you help specify what is PL?
> > 
> >> +
> >> +	return FPGA_REGION_EMPTY;
> >> +}
> >> +
> >> +static int of_fpga_region_config_enumeration(struct fpga_region *region,
> >> +					     struct fpga_region_config_info *config_info)
> >> +{
> >> +	struct of_fpga_region_priv *ovcs = region->priv;
> >> +	int err;
> >> +
> >> +	/* if it's set do not allow changes */
> >> +	if (ovcs->ovcs_id)
> >> +		return -EPERM;
> >> +
> >> +	err = request_firmware(&ovcs->fw, config_info->firmware_name, NULL);
> >> +	if (err != 0)
> >> +		goto out_err;
> >> +
> >> +	err = of_overlay_fdt_apply((void *)ovcs->fw->data, ovcs->fw->size,
> >> +				   &ovcs->ovcs_id, NULL);
> >> +	if (err < 0) {
> >> +		pr_err("%s: Failed to create overlay (err=%d)\n",
> >> +		       __func__, err);
> >> +		release_firmware(ovcs->fw);
> >> +		goto out_err;
> >> +	}
> >> +
> >> +	return 0;
> >> +
> >> +out_err:
> >> +	ovcs->ovcs_id = 0;
> >> +	ovcs->fw = NULL;
> >> +
> >> +	return err;
> >> +}
> >> +
> >> +static int of_fpga_region_config_remove(struct fpga_region *region,
> >> +					struct fpga_region_config_info *config_info)
> >> +{
> >> +	struct of_fpga_region_priv *ovcs = region->priv;
> >> +
> >> +	if (!ovcs->ovcs_id)
> >> +		return -EPERM;
> >> +
> >> +	of_overlay_remove(&ovcs->ovcs_id);
> >> +	release_firmware(ovcs->fw);
> >> +
> >> +	ovcs->ovcs_id = 0;
> >> +	ovcs->fw = NULL;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static const struct fpga_region_ops region_ops = {
> >> +	.region_status = of_fpga_region_status,
> >> +	.region_config_enumeration = of_fpga_region_config_enumeration,
> >> +	.region_remove = of_fpga_region_config_remove,
> >> +};
> >> +
> >>  static int of_fpga_region_probe(struct platform_device *pdev)
> >>  {
> >>  	struct device *dev = &pdev->dev;
> >>  	struct device_node *np = dev->of_node;
> >> +	struct of_fpga_region_priv *priv;
> >>  	struct fpga_region *region;
> >>  	struct fpga_manager *mgr;
> >>  	int ret;
> >>  
> >> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >> +	if (!priv)
> >> +		return -ENOMEM;
> >> +
> >> +	priv->dev = dev;
> >> +
> >>  	/* Find the FPGA mgr specified by region or parent region. */
> >>  	mgr = of_fpga_region_get_mgr(np);
> >>  	if (IS_ERR(mgr))
> >>  		return -EPROBE_DEFER;
> >>  
> >> -	region = fpga_region_register(dev, mgr, of_fpga_region_get_bridges);
> >> +	region = fpga_region_register_with_ops(dev, mgr, &region_ops, priv,
> >> +					       of_fpga_region_get_bridges);
> >>  	if (IS_ERR(region)) {
> >>  		ret = PTR_ERR(region);
> >>  		goto eprobe_mgr_put;
> >> diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
> >> index 5fbc05fe70a6..3a3ba6dbb5e1 100644
> >> --- a/include/linux/fpga/fpga-region.h
> >> +++ b/include/linux/fpga/fpga-region.h
> >> @@ -6,15 +6,35 @@
> >>  #include <linux/device.h>
> >>  #include <linux/fpga/fpga-mgr.h>
> >>  #include <linux/fpga/fpga-bridge.h>
> >> +#include <linux/fpga-region.h>
> >> +#include <linux/miscdevice.h>
> >>  
> >>  struct fpga_region;
> >>  
> >> +/**
> >> + * struct fpga_region_ops - ops for low level FPGA region ops for device
> >> + * enumeration/removal
> >> + * @region_status: returns the FPGA region status
> >> + * @region_config_enumeration: Configure and enumerate the FPGA region.
> >> + * @region_remove: Remove all devices within the FPGA region
> >> + * (which are added as part of the enumeration).
> >> + */
> >> +struct fpga_region_ops {
> >> +	int (*region_status)(struct fpga_region *region);
> >> +	int (*region_config_enumeration)(struct fpga_region *region,
> >> +					 struct fpga_region_config_info *config_info);
> > 
> > My current concern is still about this combined API, it just offloads
> > all work to low level, but we have some common flows. That's why we
> > introduce a common FPGA reprograming API.
> > 
> > I didn't see issue about the vendor specific pre configuration. They
> > are generally needed to initialize the struct fpga_image_info, which
> > is a common structure for fpga_region_program_fpga().
> > 
> > For port IDs(AFU) inputs for DFL, I think it could also be changed
> > (Don't have to be implemented in this patchset). Previously DFL
> > provides an uAPI for the whole device, so it needs a port_id input to
> > position which fpga_region within the device for programming. But now,
> > we are introducing a per fpga_region programming interface, IIUC port_id
> > should not be needed anymore.
> > 
> > The combined API is truly simple for leveraging the existing
> > of-fpga-region overlay apply mechanism. But IMHO that flow doesn't fit
> > our new uAPI well. That flow is to adapt the generic configfs overlay
> > interface, which comes to a dead end as you mentioned.
> > 
> > My gut feeling for the generic programing flow should be:
> > 
> >  1. Program the image to HW.
> >  2. Enumerate the programmed image (apply the DT overlay)
> > 
> > Why we have to:
> > 
> >  1. Start enumeration.
> >  2. On pre enumeration, programe the image.
> >  3. Real enumeration.
> 
> I'm currently working on an RFC to propose a rework of the fpga
> subsystem in order to make it more aligned with the device model. One of
> the ideas I'm experimenting with is having a bus (struct bus_type) for
> fpga regions (devices) so that we can have region drivers that could
> handle internal device enumeration/management whenever a new region is
> configured on the fabric. Does this make sense in your opinions?

mm.. I didn't fully understand the need to have a region driver, what's
the issue to solve?

Thanks,
Yilun

> 
> Concerning the reconfiguration, wouldn't it be cleaner to use a
> per-region sysfs interface at fpga-region level? It would still work
> for both OF & non-OF cases.
> 
> Thanks,
> Marco
> 
> 

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