[RFCv2 3/3] reset: reset-zynq: Adding support for Xilinx Zynq reset controller.

[Philipp Zabel]

Hi Moritz,

Am Freitag, den 24.07.2015, 17:21 -0700 schrieb Moritz Fischer:
> This adds a reset controller driver to control the Xilinx Zynq
> SoC's various resets.
> 
> Signed-off-by: Moritz Fischer <moritz.fischer at ettus.com>
> ---
>  drivers/reset/Makefile     |   1 +
>  drivers/reset/reset-zynq.c | 142 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 143 insertions(+)
>  create mode 100644 drivers/reset/reset-zynq.c
> 
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 157d421..3fe50e7 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.o
> diff --git a/drivers/reset/reset-zynq.c b/drivers/reset/reset-zynq.c
> new file mode 100644
> index 0000000..05e37f8
> --- /dev/null
> +++ b/drivers/reset/reset-zynq.c
> @@ -0,0 +1,142 @@
> +/*
> + * Copyright (c) 2015, National Instruments Corp.
> + *
> + * Xilinx Zynq Reset controller driver
> + *
> + * 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; version 2 of the License.
> + *
> + * 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_RST_CTRL_OFFSET	0x200 /* FPGA Software Reset Control */

Maybe get this value from the reg property? I'm not sure if this is ever
expected to change.

> +#define NBANKS	18

reg = <0x200 0x50> says there are two more registers, are those not used?

> +struct zynq_reset_data {
> +	struct regmap *slcr;
> +	struct reset_controller_dev rcdev;
> +};
> +
> +#define to_zynq_reset_data(p)		\
> +	container_of((p), struct zynq_reset_data, rcdev)
> +
> +static int zynq_reset_assert(struct reset_controller_dev *rcdev,
> +			     unsigned long id)
> +{
> +	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
> +
> +	int bank = id / BITS_PER_LONG;
> +	int offset = id % BITS_PER_LONG;
> +
> +	regmap_update_bits(priv->slcr,
> +			   SLCR_RST_CTRL_OFFSET + (bank * 4),
> +			   BIT(offset),
> +			   BIT(offset));
> +
> +	return 0;
> +}

Just "return regmap_update_bits(...)" here ...

> +static int zynq_reset_deassert(struct reset_controller_dev *rcdev,
> +			       unsigned long id)
> +{
> +	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
> +
> +	int bank = id / BITS_PER_LONG;
> +	int offset = id % BITS_PER_LONG;
> +
> +	regmap_update_bits(priv->slcr,
> +			   SLCR_RST_CTRL_OFFSET + (bank * 4),
> +			   BIT(offset),
> +			   ~BIT(offset));
> +
> +	return 0;
> +}

... and here.

> +static int zynq_reset_status(struct reset_controller_dev *rcdev,
> +			     unsigned long id)
> +{
> +	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
> +
> +	int bank = id / BITS_PER_LONG;
> +	int offset = id % BITS_PER_LONG;
> +	u32 reg;
> +
> +	regmap_read(priv->slcr, SLCR_RST_CTRL_OFFSET + (bank * 4), &reg);
> +
> +	return !(reg & BIT(offset));
> +}

Do I understand this correctly, you write 1 to assert the reset, but the
register reads 0 while the reset is asserted and 1 otherwise?
Also note that reset_status may return negative ERRNO, so for offset ==
31 you should not return (1<<31).

> +static const struct reset_control_ops zynq_reset_ops = {
> +	.assert		= zynq_reset_assert,
> +	.deassert	= zynq_reset_deassert,
> +	.status		= zynq_reset_status,
> +};
> +
> +static int zynq_reset_probe(struct platform_device *pdev)
> +{
> +	struct zynq_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");

I'd just use syscon_node_to_regmap(pdev->dev.of_node->parent) here,
which removes the need for the syscon phandle binding.

> +	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 = NBANKS * BITS_PER_LONG;
> +	priv->rcdev.ops = &zynq_reset_ops;
> +	priv->rcdev.of_node = pdev->dev.of_node;
> +	reset_controller_register(&priv->rcdev);
> +
> +	return 0;
> +}
> +
> +static int zynq_reset_remove(struct platform_device *pdev)
> +{
> +	struct zynq_reset_data *priv = platform_get_drvdata(pdev);
> +
> +	reset_controller_unregister(&priv->rcdev);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id zynq_reset_dt_ids[] = {
> +	{ .compatible = "xlnx,zynq-reset", },
> +	{ /* sentinel */ },
> +};
> +
> +static struct platform_driver zynq_reset_driver = {
> +	.probe	= zynq_reset_probe,
> +	.remove	= zynq_reset_remove,
> +	.driver = {
> +		.name		= "zynq-pl-reset",

Is -pl- a leftover?

> +		.of_match_table	= zynq_reset_dt_ids,
> +	},
> +};
> +module_platform_driver(zynq_reset_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Moritz Fischer <moritz.fischer at ettus.com>");
> +MODULE_DESCRIPTION("Zynq Reset Controller Driver");

regards
Philipp