Re: [PATCH v9 6/7] staging: add simple-fpga-bus

Moritz Fischer
2015-07-23T21:55:52Z

Hi Alan,

I saw that your socfpga driver doesn't support the partial reconfig
use case (not a big deal).
What I currently do for Zynq is if I'm doing a non-partial reconfig is
that I disable input
level shifters and assert *all* resets while reprogramming in my FPGA
manager .write_init() and .write_complete().
For a partial reconfig use case that obviously doesn't work, since I
don't want to
bring down the entire interconnect.
In a partial reconfiguration situation, would I have separate simple-fpga buses
for each of the parts that I swap out, each with it's own reset and
bitfile attached?

On Fri, Jul 17, 2015 at 8:51 AM, <atull@opensource.altera.com> wrote:
> From: Alan Tull <atull@opensource.altera.com>
>
> Add simple fpga bus. This is a bus that configures an fpga and its
> bridges before populating the devices below it. This is intended
> for use with device tree overlays.
>
> Note that FPGA bridges are seen as reset controllers so no special
> framework for FPGA bridges will need to be added.
>
> This supports fpga use where hardware blocks on a fpga will need
> drivers (as opposed to fpga used as an acceleration without drivers.)
>
> Signed-off-by: Alan Tull <atull@opensource.altera.com>
> ---
> drivers/staging/fpga/Kconfig | 11 ++
> drivers/staging/fpga/Makefile | 1 +
> drivers/staging/fpga/simple-fpga-bus.c | 323 ++++++++++++++++++++++++++++++++
> 3 files changed, 335 insertions(+)
> create mode 100644 drivers/staging/fpga/simple-fpga-bus.c
>
> diff --git a/drivers/staging/fpga/Kconfig b/drivers/staging/fpga/Kconfig
> index 8254ca0..8d003e3 100644
> --- a/drivers/staging/fpga/Kconfig
> +++ b/drivers/staging/fpga/Kconfig
> @@ -11,4 +11,15 @@ config FPGA
> kernel. The FPGA framework adds a FPGA manager class and FPGA
> manager drivers.
>
> +if FPGA
> +
> +config SIMPLE_FPGA_BUS
> + bool "Simple FPGA Bus"
> + depends on OF
> + help
> + Simple FPGA Bus allows loading FPGA images under control of
> + Device Tree.
> +
> +endif # FPGA
> +
> endmenu
> diff --git a/drivers/staging/fpga/Makefile b/drivers/staging/fpga/Makefile
> index 3313c52..6115213 100644
> --- a/drivers/staging/fpga/Makefile
> +++ b/drivers/staging/fpga/Makefile
> @@ -4,5 +4,6 @@
>
> # Core FPGA Manager Framework
> obj-$(CONFIG_FPGA) += fpga-mgr.o
> +obj-$(CONFIG_SIMPLE_FPGA_BUS) += simple-fpga-bus.o
>
> # FPGA Manager Drivers
> diff --git a/drivers/staging/fpga/simple-fpga-bus.c b/drivers/staging/fpga/simple-fpga-bus.c
> new file mode 100644
> index 0000000..bf178d8
> --- /dev/null
> +++ b/drivers/staging/fpga/simple-fpga-bus.c
> @@ -0,0 +1,323 @@
> +/*
> + * Simple FPGA Bus
> + *
> + * Copyright (C) 2013-2015 Altera Corporation
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/fpga/fpga-mgr.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/reset.h>
> +#include <linux/slab.h>
> +
> +/**
> + * struct simple_fpga_bus - simple fpga bus private data
> + * @dev: device from pdev
> + * @mgr: the fpga manager associated with this bus
> + * @bridges: an array of reset controls for controlling FPGA bridges
> + * associated with this bus
> + * @num_bridges: size of the bridges array
> + */
> +struct simple_fpga_bus {
> + struct device *dev;
> + struct fpga_manager *mgr;
> + struct reset_control **bridges;
> + int num_bridges;
> +};
> +
> +/**
> + * simple_fpga_bus_get_mgr - get associated fpga manager
> + * @priv: simple fpga bus private data
> + * pointer to fpga manager in priv->mgr on success
> + *
> + * Given a simple fpga bus, get a reference to its the fpga manager specified
> + * by its "fpga-mgr" device tree property.
> + *
> + * Return: 0 if success or if the fpga manager is not specified.
> + * Negative error code otherwise.
> + */
> +static int simple_fpga_bus_get_mgr(struct simple_fpga_bus *priv)
> +{
> + struct device *dev = priv->dev;
> + struct device_node *np = dev->of_node;
> + struct fpga_manager *mgr;
> + struct device_node *mgr_node;
> +
> + /*
> + * Return 0 (not an error) if fpga manager is not specified.
> + * This supports the case where fpga was already configured.
> + */
> + mgr_node = of_parse_phandle(np, "fpga-mgr", 0);
> + if (!mgr_node) {
> + dev_dbg(dev, "could not find fpga-mgr DT property\n");
> + return 0;
> + }
> +
> + mgr = of_fpga_mgr_get(mgr_node);
> + if (IS_ERR(mgr))
> + return PTR_ERR(mgr);
> +
> + priv->mgr = mgr;
> +
> + return 0;
> +}
> +
> +/**
> + * simple_fpga_bus_load_image - load an fpga image under device tree control
> + * @priv: simple fpga bus private data
> + *
> + * Given a simple fpga bus, load the fpga image specified in its device
> + * tree node.
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static int simple_fpga_bus_load_image(struct simple_fpga_bus *priv)
> +{
> + struct device *dev = priv->dev;
> + struct device_node *np = dev->of_node;
> + struct fpga_manager *mgr = priv->mgr;
> + u32 flags = 0;
> + const char *path;
> +
> + if (of_property_read_bool(np, "partial-reconfig"))
> + flags |= FPGA_MGR_PARTIAL_RECONFIG;
> +
> + /* If firmware image is specified in the DT, load it */
> + if (!of_property_read_string(np, "fpga-firmware", &path))
> + return fpga_mgr_firmware_load(mgr, flags, path);
> +
> + /*
> + * Here we can add other methods of getting ahold of a fpga image
> + * specified in the device tree and programming it.
> + */
> +
> + dev_info(dev, "No FPGA image to load.\n");
> +
> + /* Status is that we have a fpga manager but no image specified. */
> + return -EINVAL;
> +}
> +
> +/**
> + * simple_fpga_bus_bridge_enable - enable the fpga bridges
> + * @priv: simple fpga bus private data
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static int simple_fpga_bus_bridge_enable(struct simple_fpga_bus *priv)
> +{
> + int i, ret;
> +
> + for (i = 0; i < priv->num_bridges; i++) {
> + ret = reset_control_deassert(priv->bridges[i]);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * simple_fpga_bus_bridge_disable - disable the bridges
> + * @priv: simple fpga bus private data
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static int simple_fpga_bus_bridge_disable(struct simple_fpga_bus *priv)
> +{
> + int i, ret;
> +
> + for (i = 0; i < priv->num_bridges; i++) {
> + ret = reset_control_assert(priv->bridges[i]);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * simple_fpga_bus_get_bridges - get references for fpga bridges
> + * @priv: simple fpga bus private data
> + *
> + * Given a simple fpga bus, get references for its associated fpga bridges so
> + * that it can enable/disable the bridges. These are specified by "resets"
> + * and "reset-names" device tree properties.
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static int simple_fpga_bus_get_bridges(struct simple_fpga_bus *priv)
> +{
> + struct device *dev = priv->dev;
> + struct device_node *np = dev->of_node;
> + const char *reset_name;
> + struct reset_control **bridges;
> + int i, num_resets, num_names, ret;
> +
> + num_resets = of_count_phandle_with_args(np, "resets", "#reset-cells");
> + num_names = of_property_count_strings(np, "reset-names");
> + if (num_resets <= 0 || num_names <= 0) {
> + dev_info(dev, "No fpga bridge resets found\n");
> + return -EINVAL;
> + }
> + if (num_resets != num_names) {
> + dev_dbg(dev, "Number of resets and reset-names differ.");
> + return -EINVAL;
> + }
> +
> + bridges = kcalloc(num_resets, sizeof(struct reset_control *),
> + GFP_KERNEL);
> + if (!bridges)
> + return -ENOMEM;
> +
> + for (i = 0; i < num_resets; i++) {
> + ret = of_property_read_string_index(np, "reset-names", i,
> + &reset_name);
> + if (ret)
> + return ret;
> +
> + bridges[i] = of_reset_control_get(np, reset_name);
> + if (IS_ERR(bridges[i])) {
> + ret = PTR_ERR(bridges[i]);
> + goto err_free_bridges;
> + }
> + }
> +
> + priv->bridges = bridges;
> + priv->num_bridges = num_resets;
> +
> + return 0;
> +
> +err_free_bridges:
> + for (i = 0; i < num_resets; i++)
> + reset_control_put(priv->bridges[i]);
> +
> + kfree(bridges);
> + return ret;
> +}
> +
> +/**
> + * simple_fpga_bus_put_bridges - release references for the fpga bridges
> + * @priv: simple fpga bus private data
> + */
> +static void simple_fpga_bus_put_bridges(struct simple_fpga_bus *priv)
> +{
> + int i;
> +
> + for (i = 0; i < priv->num_bridges; i++)
> + reset_control_put(priv->bridges[i]);
> +
> + kfree(priv->bridges);
> + priv->num_bridges = 0;
> +}
> +
> +/**
> + * simple_fpga_bus_probe - Probe function for simple fpga bus.
> + * @pdev: platform device
> + *
> + * Do the necessary steps to program the FPGA and enable associated bridges.
> + * Then populate the device tree below this bus to get drivers probed for the
> + * hardware that is on the FPGA.
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +static int simple_fpga_bus_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device_node *np = dev->of_node;
> + struct simple_fpga_bus *priv;
> + int ret;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->dev = dev;
> +
> + ret = simple_fpga_bus_get_mgr(priv);
> + if (ret)
> + return ret;
> +
> + if (priv->mgr) {
> + ret = simple_fpga_bus_get_bridges(priv);
See below.
> + if (ret)
> + goto err_release_mgr;
> +
> + ret = simple_fpga_bus_load_image(priv);
> + if (ret)
> + goto err_release_br;
> +
> + ret = simple_fpga_bus_bridge_enable(priv);
In my tests I never saw an actual disable happen. This might be a bug
in my reset controller driver,
if that's the case please ignore my nit ;-) But wouldn't you want to
assert while reconfiguring?
> + if (ret)
> + goto err_release_br;
> + }
> +
> + of_platform_populate(np, of_default_bus_match_table, NULL, dev);
> +
> + platform_set_drvdata(pdev, priv);
> +
> + return 0;
> +
> +err_release_br:
> + simple_fpga_bus_put_bridges(priv);
> +err_release_mgr:
> + fpga_mgr_put(priv->mgr);
> +
> + return ret;
> +}
> +
> +static int simple_fpga_bus_remove(struct platform_device *pdev)
> +{
> + struct simple_fpga_bus *priv = platform_get_drvdata(pdev);
> +
> + simple_fpga_bus_bridge_disable(priv);
> + simple_fpga_bus_put_bridges(priv);
> + fpga_mgr_put(priv->mgr);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id simple_fpga_bus_of_match[] = {
> + { .compatible = "simple-fpga-bus", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, simple_fpga_bus_of_match);
> +
> +static struct platform_driver simple_fpga_bus_driver = {
> + .probe = simple_fpga_bus_probe,
> + .remove = simple_fpga_bus_remove,
> + .driver = {
> + .name = "simple-fpga-bus",
> + .owner = THIS_MODULE,
> + .of_match_table = of_match_ptr(simple_fpga_bus_of_match),
> + },
> +};
> +
> +static int __init simple_fpga_bus_init(void)
> +{
> + return platform_driver_register(&simple_fpga_bus_driver);
> +}
> +
> +static void __exit simple_fpga_bus_exit(void)
> +{
> + platform_driver_unregister(&simple_fpga_bus_driver);
> +}
> +
> +module_init(simple_fpga_bus_init);
> +module_exit(simple_fpga_bus_exit);
> +
> +MODULE_DESCRIPTION("Simple FPGA Bus");
> +MODULE_AUTHOR("Alan Tull <atull@opensource.altera.com>");
> +MODULE_LICENSE("GPL v2");
> --
> 1.7.9.5
>
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Cheers,

Moritz