Re: [RFC PATCH v2 3/4] fpga: add fake FPGA region

From: Xu Yilun
Date: Sat Mar 25 2023 - 03:23:19 EST

On 2023-03-21 at 21:07:43 +0100, Marco Pagani wrote:
>
>
> On 2023-03-17 11:40, Xu Yilun wrote:
> > On 2023-03-10 at 18:04:11 +0100, Marco Pagani wrote:
> >> Add fake FPGA region platform driver with support functions. This
> >> module is part of the KUnit tests for the FPGA subsystem.
> >>
> >> Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
> >> ---
> >> drivers/fpga/tests/fake-fpga-region.c | 219 ++++++++++++++++++++++++++
> >> drivers/fpga/tests/fake-fpga-region.h | 38 +++++
> >> 2 files changed, 257 insertions(+)
> >> create mode 100644 drivers/fpga/tests/fake-fpga-region.c
> >> create mode 100644 drivers/fpga/tests/fake-fpga-region.h
> >>
> >> diff --git a/drivers/fpga/tests/fake-fpga-region.c b/drivers/fpga/tests/fake-fpga-region.c
> >> new file mode 100644
> >> index 000000000000..54d0e564728b
> >> --- /dev/null
> >> +++ b/drivers/fpga/tests/fake-fpga-region.c
> >> @@ -0,0 +1,219 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Driver for the fake FPGA region
> >> + *
> >> + * Copyright (C) 2023 Red Hat, Inc.
> >> + *
> >> + * Author: Marco Pagani <marpagan@xxxxxxxxxx>
> >> + */
> >> +
> >> +#include <linux/device.h>
> >> +#include <linux/list.h>
> >> +#include <linux/platform_device.h>
> >> +#include <linux/fpga/fpga-mgr.h>
> >> +#include <linux/fpga/fpga-region.h>
> >> +#include <linux/fpga/fpga-bridge.h>
> >> +#include <kunit/test.h>
> >> +
> >> +#include "fake-fpga-region.h"
> >> +
> >> +#define FAKE_FPGA_REGION_DEV_NAME "fake_fpga_region"
> >> +
> >> +struct fake_region_priv {
> >> + int id;
> >> + struct kunit *test;
> >> + struct list_head bridge_list;
> >> +};
> >> +
> >> +struct fake_region_data {
> >> + struct fpga_manager *mgr;
> >> + struct kunit *test;
> >> +};
> >> +
> >> +/**
> >> + * fake_fpga_region_register() - register a fake FPGA region.
> >> + * @region_ctx: fake FPGA region context data structure.
> >> + * @mgr: associated FPGA manager.
> >> + * @parent: parent device.
> >> + * @test: KUnit test context object.
> >> + *
> >> + * Return: 0 if registration succeeded, an error code otherwise.
> >> + */
> >> +int fake_fpga_region_register(struct fake_fpga_region *region_ctx,
> >> + struct fpga_manager *mgr, struct device *parent,
> >> + struct kunit *test)
> >> +{
> >> + struct fake_region_data pdata;
> >> + struct fake_region_priv *priv;
> >> + int ret;
> >> +
> >> + pdata.mgr = mgr;
> >> + pdata.test = test;
> >> +
> >> + region_ctx->pdev = platform_device_alloc(FAKE_FPGA_REGION_DEV_NAME,
> >> + PLATFORM_DEVID_AUTO);
> >> + if (IS_ERR(region_ctx->pdev)) {
> >> + pr_err("Fake FPGA region device allocation failed\n");
> >> + return -ENOMEM;
> >> + }
> >> +
> >> + region_ctx->pdev->dev.parent = parent;
> >> + platform_device_add_data(region_ctx->pdev, &pdata, sizeof(pdata));
> >> +
> >> + ret = platform_device_add(region_ctx->pdev);
> >> + if (ret) {
> >> + pr_err("Fake FPGA region device add failed\n");
> >> + platform_device_put(region_ctx->pdev);
> >> + return ret;
> >> + }
> >> +
> >> + region_ctx->region = platform_get_drvdata(region_ctx->pdev);
> >> +
> >> + if (test) {
> >> + priv = region_ctx->region->priv;
> >> + kunit_info(test, "Fake FPGA region %d registered\n", priv->id);
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +EXPORT_SYMBOL_GPL(fake_fpga_region_register);
> >> +
> >> +/**
> >> + * fake_fpga_region_unregister() - unregister a fake FPGA region.
> >> + * @region_ctx: fake FPGA region context data structure.
> >> + */
> >> +void fake_fpga_region_unregister(struct fake_fpga_region *region_ctx)
> >> +{
> >> + struct fake_region_priv *priv;
> >> + struct kunit *test;
> >> + int id;
> >> +
> >> + if (!region_ctx)
> >> + return;
> >> +
> >> + priv = region_ctx->region->priv;
> >> + test = priv->test;
> >> + id = priv->id;
> >> +
> >> + if (region_ctx->pdev) {
> >> + platform_device_unregister(region_ctx->pdev);
> >> + if (test)
> >> + kunit_info(test, "Fake FPGA region %d unregistered\n", id);
> >> + }
> >> +}
> >> +EXPORT_SYMBOL_GPL(fake_fpga_region_unregister);
> >> +
> >> +/**
> >> + * fake_fpga_region_add_bridge() - add a bridge to a fake FPGA region.
> >> + * @region_ctx: fake FPGA region context data structure.
> >> + * @bridge: FPGA bridge.
> >> + *
> >> + * Return: 0 if registration succeeded, an error code otherwise.
> >> + */
> >> +void fake_fpga_region_add_bridge(struct fake_fpga_region *region_ctx,
> >> + struct fpga_bridge *bridge)
> >> +{
> >> + struct fake_region_priv *priv;
> >> +
> >> + priv = region_ctx->region->priv;
> >> +
> >> + /* Add bridge to the list of bridges in the private context */
> >> + list_add(&bridge->node, &priv->bridge_list);
> >> +
> >> + if (priv->test)
> >> + kunit_info(priv->test, "Bridge added to fake FPGA region %d\n",
> >> + priv->id);
> >> +}
> >> +EXPORT_SYMBOL_GPL(fake_fpga_region_add_bridge);
> >> +
> >> +static int fake_region_get_bridges(struct fpga_region *region)
> >> +{
> >> + struct fake_region_priv *priv;
> >> + struct fpga_bridge *bridge, *tmp;
> >> + int ret;
> >> +
> >> + priv = region->priv;
> >> +
> >> + list_for_each_entry_safe(bridge, tmp, &priv->bridge_list, node) {
> >> + list_del(&bridge->node);
> >
> > I think the fake_fpga_region user just need to call
> > fake_fpga_region_add_bridge() once on init, and may call
> > fpga_bridges_put() at any time after fpga_region_program_fpga(), then
> > you may lose the track of the bridges, which breaks the next
> > fpga_region_program_fpga().
> >
> > Thanks,
> > Yilun
> >
>
> That's right, fake_fpga_region_add_bridge() is intended to be called once
> (for each bridge) just after registering the region. I should have added
> this to the kernel-doc description of the function.
>
> When a fake region is unregistered, its bridges are released using
> fpga_bridges_put() by the remove method of the platform driver.

Please check the kernel-doc:

/**
* fpga_region_program_fpga - program FPGA
*
* @region: FPGA region
*
* Program an FPGA using fpga image info (region->info).
* If the region has a get_bridges function, the exclusive reference for the
* bridges will be held if programming succeeds. This is intended to prevent
* reprogramming the region until the caller considers it safe to do so.
* The caller will need to call fpga_bridges_put() before attempting to
* reprogram the region.
*
* Return 0 for success or negative error code.
*/
int fpga_region_program_fpga(struct fpga_region *region)

That means the fpga test should call fpga_bridges_put() before a second
fpga_region_program_fpga().

>
> In the fpga_test_static_cfg test case, the base region is configured
> twice. Then, when the base region is unregistered by the exit method of
> the test suite, the base bridge is released.
>
> Here's the raw test output with dev_dbg() prints of the FPGA bridge
> enabled:
>
> # Subtest: fpga
> 1..2
> # fpga_test_static_cfg: Fake FPGA manager: state
> # fpga_test_static_cfg: Fake FPGA manager registered
> # fpga_test_static_cfg: Fake FPGA bridge 3 registered
> # fpga_test_static_cfg: Fake FPGA region 0 registered
> # fpga_test_static_cfg: Bridge added to fake FPGA region 0
> # fpga_test_static_cfg: FPGA base system built
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_show
> # fpga_test_static_cfg: FPGA image allocated in a buffer, size: 16384
> fpga_bridge br0: get <---
> fpga_bridge br0: disable
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_set: 0
> # fpga_test_static_cfg: Fake FPGA manager: parse_header
> # fpga_test_static_cfg: Fake FPGA manager: write_init
> # fpga_test_static_cfg: Fake FPGA manager: write
> # fpga_test_static_cfg: Fake FPGA manager: write_complete
> fpga_bridge br0: enable
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_set: 1
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_show
> # fpga_test_static_cfg: FPGA configuration completed using a buffer image
> # fpga_test_static_cfg: FPGA image allocated in a scatter gather table, size: 16384
> fpga_bridge br0: disable
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_set: 0
> # fpga_test_static_cfg: Fake FPGA manager: parse_header
> # fpga_test_static_cfg: Fake FPGA manager: write_init
> # fpga_test_static_cfg: Fake FPGA manager: write_sg
> # fpga_test_static_cfg: Fake FPGA manager: write_complete
> fpga_bridge br0: enable
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_set: 1
> # fpga_test_static_cfg: Fake FPGA bridge 3: enable_show
> # fpga_test_static_cfg: FPGA configuration completed using scatter gather table image
> fpga_bridge br0: put <---
> # fpga_test_static_cfg: Fake FPGA region 0 unregistered
> # fpga_test_static_cfg: Fake FPGA bridge: remove
> # fpga_test_static_cfg: Fake FPGA bridge 3 unregistered
> fpga_manager fpga0: fpga_mgr_unregister Fake FPGA Manager
> # fpga_test_static_cfg: Fake FPGA manager: remove
> # fpga_test_static_cfg: Fake FPGA manager unregistered
> ok 1 fpga_test_static_cfg
>
> In my understanding, of-region uses a similar approach by releasing
> bridges only when the overlay is removed.

The overlay removal is not equal to the of-fpga-region removal. Actually
the overlay could be applied & removed multiple times, and
fpga_region_program_fpga & fpga_bridges_put() are called each time.


Thanks,
Yilun

>
>
> >> + ret = fpga_bridge_get_to_list(bridge->dev.parent,
> >> + region->info,
> >> + &region->bridge_list);
> >> + if (ret)
> >> + break;
> >> + }
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static int fake_fpga_region_probe(struct platform_device *pdev)
> >> +{
> >> + struct device *dev;
> >> + struct fpga_region *region;
> >> + struct fpga_manager *mgr;
> >> + struct fake_region_data *pdata;
> >> + struct fake_region_priv *priv;
> >> + struct fpga_region_info info;
> >> + static int id_count;
> >> +
> >> + dev = &pdev->dev;
> >> + pdata = dev_get_platdata(dev);
> >> +
> >> + if (!pdata) {
> >> + dev_err(&pdev->dev, "Missing platform data\n");
> >> + return -EINVAL;
> >> + }
> >> +
> >> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> >> + if (!priv)
> >> + return -ENOMEM;
> >> +
> >> + mgr = fpga_mgr_get(pdata->mgr->dev.parent);
> >> + if (IS_ERR(mgr))
> >> + return PTR_ERR(mgr);
> >> +
> >> + INIT_LIST_HEAD(&priv->bridge_list);
> >> + priv->id = id_count++;
> >> + priv->test = pdata->test;
> >> +
> >> + memset(&info, 0, sizeof(info));
> >> + info.priv = priv;
> >> + info.mgr = mgr;
> >> + info.get_bridges = fake_region_get_bridges;
> >> +
> >> + region = fpga_region_register_full(dev, &info);
> >> + if (IS_ERR(region)) {
> >> + fpga_mgr_put(mgr);
> >> + return PTR_ERR(region);
> >> + }
> >> +
> >> + platform_set_drvdata(pdev, region);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int fake_fpga_region_remove(struct platform_device *pdev)
> >> +{
> >> + struct fpga_region *region = platform_get_drvdata(pdev);
> >> + struct fpga_manager *mgr = region->mgr;
> >> +
> >> + fpga_mgr_put(mgr);
> >> + fpga_bridges_put(&region->bridge_list);
> >> + fpga_region_unregister(region);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static struct platform_driver fake_fpga_region_drv = {
> >> + .driver = {
> >> + .name = FAKE_FPGA_REGION_DEV_NAME
> >> + },
> >> + .probe = fake_fpga_region_probe,
> >> + .remove = fake_fpga_region_remove,
> >> +};
> >> +
> >> +module_platform_driver(fake_fpga_region_drv);
> >> +
> >> +MODULE_AUTHOR("Marco Pagani <marpagan@xxxxxxxxxx>");
> >> +MODULE_DESCRIPTION("Fake FPGA Bridge");
> >> +MODULE_LICENSE("GPL v2");
> >> diff --git a/drivers/fpga/tests/fake-fpga-region.h b/drivers/fpga/tests/fake-fpga-region.h
> >> new file mode 100644
> >> index 000000000000..9268ca335662
> >> --- /dev/null
> >> +++ b/drivers/fpga/tests/fake-fpga-region.h
> >> @@ -0,0 +1,38 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +/*
> >> + * Header file for the fake FPGA region
> >> + *
> >> + * Copyright (C) 2023 Red Hat, Inc.
> >> + *
> >> + * Author: Marco Pagani <marpagan@xxxxxxxxxx>
> >> + */
> >> +
> >> +#ifndef __FPGA_FAKE_RGN_H
> >> +#define __FPGA_FAKE_RGN_H
> >> +
> >> +#include <linux/platform_device.h>
> >> +#include <kunit/test.h>
> >> +#include <linux/fpga/fpga-mgr.h>
> >> +#include <linux/fpga/fpga-bridge.h>
> >> +
> >> +/**
> >> + * struct fake_fpga_region - fake FPGA region context data structure
> >> + *
> >> + * @region: FPGA region.
> >> + * @pdev: platform device of the FPGA region.
> >> + */
> >> +struct fake_fpga_region {
> >> + struct fpga_region *region;
> >> + struct platform_device *pdev;
> >> +};
> >> +
> >> +int fake_fpga_region_register(struct fake_fpga_region *region_ctx,
> >> + struct fpga_manager *mgr, struct device *parent,
> >> + struct kunit *test);
> >> +
> >> +void fake_fpga_region_add_bridge(struct fake_fpga_region *region_ctx,
> >> + struct fpga_bridge *bridge);
> >> +
> >> +void fake_fpga_region_unregister(struct fake_fpga_region *region_ctx);
> >> +
> >> +#endif /* __FPGA_FAKE_RGN_H */
> >> --
> >> 2.39.2
> >>
> >
>
> Thanks,
> Marco
>