[RFC 3/3] reset: reset-zynq-pl: Adding support for Xilinx Zynq PL reset.

[Sören Brinkmann]

Hi Moritz,

On Thu, 2015-07-23 at 03:51PM -0700, Moritz Fischer wrote:
> The Zynq PL reset controller allows to control the 4
> FCLK{0..3}_RESETN signals that can be used to reset custom IP in
> the PL.
> 
> Signed-off-by: Moritz Fischer <moritz.fischer at ettus.com>
> ---
>  drivers/reset/Makefile        |   1 +
>  drivers/reset/reset-zynq-pl.c | 142 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 143 insertions(+)
>  create mode 100644 drivers/reset/reset-zynq-pl.c
> 
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 157d421..5c86f92 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -3,3 +3,4 @@ obj-$(CONFIG_ARCH_SOCFPGA) += reset-socfpga.o
>  obj-$(CONFIG_ARCH_BERLIN) += reset-berlin.o
>  obj-$(CONFIG_ARCH_SUNXI) += reset-sunxi.o
>  obj-$(CONFIG_ARCH_STI) += sti/
> +obj-$(CONFIG_ARCH_ZYNQ) += reset-zynq-pl.o
> diff --git a/drivers/reset/reset-zynq-pl.c b/drivers/reset/reset-zynq-pl.c
> new file mode 100644
> index 0000000..3e04ab0
> --- /dev/null
> +++ b/drivers/reset/reset-zynq-pl.c
> @@ -0,0 +1,142 @@
> +/*
> + * Xilinx Zynq PL Reset Controller
> + *
> + * Copyright (c) 2015, National Instruments Corp.
> + * Author: Moritz Fischer <moritz.fischer at ettus.com>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation; either version 2 of
> + * the License, or (at your option) any later version.

Here you allow GPLv2 and later, whereas in the LICENSE macro you only
allow GPLv2. That should be in sync.

> + *
> + * This program is distributed in the hope that 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.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +
> +/* Offsets into SLCR regmap */
> +#define SLCR_FPGA_RST_CTRL_OFFSET	0x240 /* FPGA Software Reset Control */
> +
> +struct zynq_pl_reset_data {
> +	struct regmap *slcr;
> +	struct reset_controller_dev rcdev;
> +};
> +
> +static int zynq_pl_reset_assert(struct reset_controller_dev *rcdev,
> +				unsigned long id)
> +{
> +	struct zynq_pl_reset_data *priv = container_of(rcdev,
> +						struct zynq_pl_reset_data,
> +						rcdev);
> +
> +	int offset = id % BITS_PER_LONG;
> +
> +	regmap_update_bits(priv->slcr,
> +			   SLCR_FPGA_RST_CTRL_OFFSET,
> +			   BIT(offset),
> +			   BIT(offset));
> +
> +	return 0;
> +}
> +
> +static int zynq_pl_reset_deassert(struct reset_controller_dev *rcdev,
> +				  unsigned long id)
> +{
> +	struct zynq_pl_reset_data *priv = container_of(rcdev,
> +						struct zynq_pl_reset_data,
> +						rcdev);
> +
> +	int offset = id % BITS_PER_LONG;
> +
> +	regmap_update_bits(priv->slcr,
> +			   SLCR_FPGA_RST_CTRL_OFFSET,
> +			   BIT(offset),
> +			   ~BIT(offset));
> +
> +	return 0;
> +}
> +
> +static int zynq_pl_reset_status(struct reset_controller_dev *rcdev,
> +				unsigned long id)
> +{
> +	struct zynq_pl_reset_data *priv = container_of(rcdev,
> +						struct zynq_pl_reset_data,
> +						rcdev);
> +	int offset = id % BITS_PER_LONG;
> +	u32 reg;
> +
> +	regmap_read(priv->slcr, SLCR_FPGA_RST_CTRL_OFFSET, &reg);
> +
> +	return !(reg & BIT(offset));
> +}
> +
> +static const struct reset_control_ops zynq_pl_reset_ops = {
> +	.assert		= zynq_pl_reset_assert,
> +	.deassert	= zynq_pl_reset_deassert,
> +	.status		= zynq_pl_reset_status,
> +};
> +
> +static int zynq_pl_reset_probe(struct platform_device *pdev)
> +{
> +	struct zynq_pl_reset_data *priv;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +	platform_set_drvdata(pdev, priv);
> +
> +	priv->slcr = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
> +		"syscon");
> +	if (IS_ERR(priv->slcr)) {
> +		dev_err(&pdev->dev, "unable to get zynq-slcr regmap");
> +		return PTR_ERR(priv->slcr);
> +	}
> +
> +	priv->rcdev.owner = THIS_MODULE;
> +	priv->rcdev.nr_resets = BITS_PER_LONG;
> +	priv->rcdev.ops = &zynq_pl_reset_ops;
> +	priv->rcdev.of_node = pdev->dev.of_node;
> +	reset_controller_register(&priv->rcdev);
> +
> +	return 0;
> +}
> +
> +static int zynq_pl_reset_remove(struct platform_device *pdev)
> +{
> +	struct zynq_pl_reset_data *priv = platform_get_drvdata(pdev);
> +
> +	reset_controller_unregister(&priv->rcdev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id zynq_pl_reset_dt_ids[] = {
> +	{ .compatible = "xlnx,zynq-reset-pl", },
> +	{ /* sentinel */ },
> +};
> +
> +static struct platform_driver zynq_pl_reset_driver = {
> +	.probe	= zynq_pl_reset_probe,
> +	.remove	= zynq_pl_reset_remove,
> +	.driver = {
> +		.name		= "zynq-pl-reset",
> +		.of_match_table	= zynq_pl_reset_dt_ids,
> +	},
> +};
> +module_platform_driver(zynq_pl_reset_driver);
> +
> +MODULE_LICENSE("GPL v2");

GPLv2 or GPL?

> +MODULE_AUTHOR("Moritz Fischer <moritz.fischer at ettus.com>");
> +MODULE_DESCRIPTION("Zynq PL Reset Controller Driver");
> +MODULE_ALIAS("reset:zynq-pl");

There has been some discussion around the alias. I think in most cases
it turned out to not be necessary to have.

I think overall having a reset-manager is a good thing. But as already
mentioned in the other emails, why stop at the PL? I think this should
just become the Zynq reset controller and handle all the resets in the
SLCR.

	Thanks,
	Sören