[RFC 4/6] reset: add polarfire soc reset support

[Conor Dooley]

On 19/06/2022 17:49, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley at microchip.com>
> 
> Add support for the resets on Microchip's PolarFire SoC (MPFS).
> Reset control is a single register, wedged in between registers for
> clock control. To fit with existed DT etc, the reset controller is
> created using the aux device framework & set up in the clock driver.
> 
> Signed-off-by: Conor Dooley <conor.dooley at microchip.com>
> ---
>  drivers/reset/Kconfig      |   9 +++
>  drivers/reset/Makefile     |   2 +-
>  drivers/reset/reset-mpfs.c | 155 +++++++++++++++++++++++++++++++++++++
>  3 files changed, 165 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/reset/reset-mpfs.c
> 
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index 93c8d07ee328..8f7d7cda690d 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -122,6 +122,15 @@ config RESET_MCHP_SPARX5
>  	help
>  	  This driver supports switch core reset for the Microchip Sparx5 SoC.
>  
> +config RESET_POLARFIRE_SOC
> +	bool "Microchip PolarFire SoC (MPFS) Reset Driver"
> +	depends on AUXILIARY_BUS

(Correctly) According to lkp I screwed this up, needs to depend on
MCHP_CLK_MPFS.

> +	default MCHP_CLK_MPFS
> +	help
> +	  This driver supports switch core reset for the Microchip PolarFire SoC
> +
> +	  CONFIG_RESET_MPFS
> +
>  config RESET_MESON
>  	tristate "Meson Reset Driver"
>  	depends on ARCH_MESON || COMPILE_TEST
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index a80a9c4008a7..5fac3a753858 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -17,6 +17,7 @@ obj-$(CONFIG_RESET_K210) += reset-k210.o
>  obj-$(CONFIG_RESET_LANTIQ) += reset-lantiq.o
>  obj-$(CONFIG_RESET_LPC18XX) += reset-lpc18xx.o
>  obj-$(CONFIG_RESET_MCHP_SPARX5) += reset-microchip-sparx5.o
> +obj-$(CONFIG_RESET_POLARFIRE_SOC) += reset-mpfs.o
>  obj-$(CONFIG_RESET_MESON) += reset-meson.o
>  obj-$(CONFIG_RESET_MESON_AUDIO_ARB) += reset-meson-audio-arb.o
>  obj-$(CONFIG_RESET_NPCM) += reset-npcm.o
> @@ -38,4 +39,3 @@ obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
>  obj-$(CONFIG_RESET_UNIPHIER_GLUE) += reset-uniphier-glue.o
>  obj-$(CONFIG_RESET_ZYNQ) += reset-zynq.o
>  obj-$(CONFIG_ARCH_ZYNQMP) += reset-zynqmp.o
> -
> diff --git a/drivers/reset/reset-mpfs.c b/drivers/reset/reset-mpfs.c
> new file mode 100644
> index 000000000000..6c9c10cd9077
> --- /dev/null
> +++ b/drivers/reset/reset-mpfs.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * PolarFire SoC (MPFS) Peripheral Clock Reset Controller
> + *
> + * Author: Conor Dooley <conor.dooley at microchip.com>
> + * Copyright (c) 2022 Microchip Technology Inc. and its subsidiaries.
> + *
> + */
> +#include <linux/auxiliary_bus.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset-controller.h>
> +#include <dt-bindings/clock/microchip,mpfs-clock.h>
> +#include <soc/microchip/mpfs.h>
> +
> +/*
> + * The ENVM reset is the lowest bit in the register & I am using the CLK_FOO
> + * defines in the dt to make things easier to configure - so this is accounting
> + * for the offset of 3 there.
> + */
> +#define MPFS_PERIPH_OFFSET	CLK_ENVM
> +#define MPFS_NUM_RESETS		30u
> +
> +/*
> + * Peripheral clock resets
> + */
> +
> +static int mpfs_assert(struct reset_controller_dev *rcdev, unsigned long id)
> +{
> +	u32 reg;
> +
> +	reg = mpfs_reset_read(rcdev->dev);
> +	reg |= (1u << id);
> +	mpfs_reset_write(rcdev->dev, reg);
> +
> +	dev_dbg(rcdev->dev,
> +		"Asserting reset for device with REG_SUBBLK_RESET_CR index: %u\n",
> +		id);
> +	return 0;
> +}
> +
> +static int mpfs_deassert(struct reset_controller_dev *rcdev, unsigned long id)
> +{
> +	u32 reg, val;
> +
> +	reg = mpfs_reset_read(rcdev->dev);
> +	val = reg & ~(1u << id);
> +	mpfs_reset_write(rcdev->dev, val);
> +
> +	dev_dbg(rcdev->dev,
> +		"Deasserting device with REG_SUBBLK_RESET_CR index: %u\n",
> +		id);
> +
> +	return 0;
> +}
> +
> +static int mpfs_status(struct reset_controller_dev *rcdev, unsigned long id)
> +{
> +	u32 reg = mpfs_reset_read(rcdev->dev);
> +
> +	return (reg & (1u << id));
> +}
> +
> +static int mpfs_reset(struct reset_controller_dev *rcdev, unsigned long id)
> +{
> +	dev_dbg(rcdev->dev,
> +		"Resetting device with REG_SUBBLK_RESET_CR index: %u\n",
> +		id);
> +
> +	mpfs_assert(rcdev, id);
> +
> +	/* Value is stolen from the rcar reset driver, will need changing after RFC */
> +	udelay(35);
> +
> +	mpfs_deassert(rcdev, id);
> +
> +	return 0;
> +}
> +
> +static const struct reset_control_ops mpfs_reset_ops = {
> +	.reset = mpfs_reset,
> +	.assert = mpfs_assert,
> +	.deassert = mpfs_deassert,
> +	.status = mpfs_status,
> +};
> +
> +static int mpfs_reset_xlate(struct reset_controller_dev *rcdev,
> +			    const struct of_phandle_args *reset_spec)
> +{
> +	unsigned int index = reset_spec->args[0];
> +
> +	/*
> +	 * CLK_RESERVED does not map to a clock, but it does map to a reset,
> +	 * so it has to be accounted for here. It is the reset for the fabric,
> +	 * so if this reset gets called - do not reset it.
> +	 */
> +	if (index == CLK_RESERVED) {
> +		dev_err(rcdev->dev, "Resetting the fabric is not supported\n");
> +		return -EINVAL;
> +	}
> +
> +	if (index < MPFS_PERIPH_OFFSET || index >= (MPFS_PERIPH_OFFSET + rcdev->nr_resets)) {
> +		dev_err(rcdev->dev, "Invalid reset index %u\n", reset_spec->args[0]);
> +		return -EINVAL;
> +	}
> +
> +	return index - MPFS_PERIPH_OFFSET;
> +}
> +
> +static int mpfs_reset_probe(struct auxiliary_device *adev,
> +			    const struct auxiliary_device_id *id)
> +{
> +	struct device *dev = &adev->dev;
> +	struct reset_controller_dev *rcdev;
> +	int ret;
> +
> +	rcdev = devm_kzalloc(dev, sizeof(*rcdev), GFP_KERNEL);
> +	if (!rcdev)
> +		return -ENOMEM;
> +
> +	rcdev->dev = dev;
> +	rcdev->dev->parent = adev->dev.parent;
> +	rcdev->ops = &mpfs_reset_ops;
> +	rcdev->of_node = adev->dev.parent->of_node;
> +	rcdev->of_reset_n_cells = 1;
> +	rcdev->of_xlate = mpfs_reset_xlate;
> +	rcdev->nr_resets = MPFS_NUM_RESETS;
> +
> +	ret = devm_reset_controller_register(dev, rcdev);
> +	if (!ret)
> +		dev_info(dev, "Registered MPFS reset controller\n");
> +
> +	return ret;
> +}
> +
> +static const struct auxiliary_device_id mpfs_reset_ids[] = {
> +	{
> +		.name = "clk_mpfs.reset-mpfs",
> +	},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(auxiliary, mpfs_reset_ids);
> +
> +static struct auxiliary_driver mpfs_reset_driver = {
> +	.probe		= mpfs_reset_probe,
> +	.id_table	= mpfs_reset_ids,
> +};
> +
> +module_auxiliary_driver(mpfs_reset_driver);
> +
> +MODULE_DESCRIPTION("Microchip PolarFire SoC Reset Driver");
> +MODULE_AUTHOR("Conor Dooley <conor.dooley at microchip.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS(MCHP_CLK_MPFS);