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Date:   Wed, 3 Mar 2021 09:55:45 +0100
From:   Alexandre Belloni <alexandre.belloni@bootlin.com>
To:     Steen Hegelund <steen.hegelund@microchip.com>
Cc:     Philipp Zabel <p.zabel@pengutronix.de>,
        Andrew Lunn <andrew@lunn.ch>,
        Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 2/3] reset: mchp: sparx5: add switch reset driver
Message-ID: <YD9PEaC4qsahQpcZ@piout.net>
References: <20210303081158.684532-1-steen.hegelund@microchip.com>
 <20210303081158.684532-3-steen.hegelund@microchip.com>
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In-Reply-To: <20210303081158.684532-3-steen.hegelund@microchip.com>
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On 03/03/2021 09:11:57+0100, Steen Hegelund wrote:
> The Sparx5 Switch SoC has a number of components that can be reset
> indiviually, but at least the Switch Core needs to be in a well defined
> state at power on, when any of the Sparx5 drivers starts to access the
> Switch Core, this reset driver is available.
> 
> The reset driver is loaded early via the postcore_initcall interface, and
> will then be available for the other Sparx5 drivers (SGPIO, SwitchDev etc)
> that are loaded next, and the first of them to be loaded can perform the
> one-time Switch Core reset that is needed.
> 
> The driver has protection so that the system busses, DDR controller, PCI-E
> and ARM A53 CPU and a few other subsystems are not touched by the reset.
> 
> Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

> ---
>  drivers/reset/Kconfig                  |   8 ++
>  drivers/reset/Makefile                 |   1 +
>  drivers/reset/reset-microchip-sparx5.c | 146 +++++++++++++++++++++++++
>  3 files changed, 155 insertions(+)
>  create mode 100644 drivers/reset/reset-microchip-sparx5.c
> 
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index 4171c6f76385..c26798092ccf 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -111,6 +111,14 @@ config RESET_LPC18XX
>  	help
>  	  This enables the reset controller driver for NXP LPC18xx/43xx SoCs.
>  
> +config RESET_MCHP_SPARX5
> +	bool "Microchip Sparx5 reset driver"
> +	depends on HAS_IOMEM || COMPILE_TEST
> +	default y if SPARX5_SWITCH
> +	select MFD_SYSCON
> +	help
> +	  This driver supports switch core reset for the Microchip Sparx5 SoC.
> +
>  config RESET_MESON
>  	tristate "Meson Reset Driver"
>  	depends on ARCH_MESON || COMPILE_TEST
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 65a118a91b27..c1d6aa9b1b52 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o
>  obj-$(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_MESON) += reset-meson.o
>  obj-$(CONFIG_RESET_MESON_AUDIO_ARB) += reset-meson-audio-arb.o
>  obj-$(CONFIG_RESET_NPCM) += reset-npcm.o
> diff --git a/drivers/reset/reset-microchip-sparx5.c b/drivers/reset/reset-microchip-sparx5.c
> new file mode 100644
> index 000000000000..cff39a643a14
> --- /dev/null
> +++ b/drivers/reset/reset-microchip-sparx5.c
> @@ -0,0 +1,146 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/* Microchip Sparx5 Switch Reset driver
> + *
> + * Copyright (c) 2020 Microchip Technology Inc. and its subsidiaries.
> + *
> + * The Sparx5 Chip Register Model can be browsed at this location:
> + * https://github.com/microchip-ung/sparx-5_reginfo
> + */
> +#include <linux/mfd/syscon.h>
> +#include <linux/of_device.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/reset-controller.h>
> +
> +#define PROTECT_REG    0x84
> +#define PROTECT_BIT    BIT(10)
> +#define SOFT_RESET_REG 0x00
> +#define SOFT_RESET_BIT BIT(1)
> +
> +struct mchp_reset_context {
> +	struct regmap *cpu_ctrl;
> +	struct regmap *gcb_ctrl;
> +	struct reset_controller_dev rcdev;
> +};
> +
> +static struct regmap_config sparx5_reset_regmap_config = {
> +	.reg_bits	= 32,
> +	.val_bits	= 32,
> +	.reg_stride	= 4,
> +};
> +
> +static int sparx5_switch_reset(struct reset_controller_dev *rcdev,
> +			       unsigned long id)
> +{
> +	struct mchp_reset_context *ctx =
> +		container_of(rcdev, struct mchp_reset_context, rcdev);
> +	u32 val;
> +
> +	/* Make sure the core is PROTECTED from reset */
> +	regmap_update_bits(ctx->cpu_ctrl, PROTECT_REG, PROTECT_BIT, PROTECT_BIT);
> +
> +	/* Start soft reset */
> +	regmap_write(ctx->gcb_ctrl, SOFT_RESET_REG, SOFT_RESET_BIT);
> +
> +	/* Wait for soft reset done */
> +	return regmap_read_poll_timeout(ctx->gcb_ctrl, SOFT_RESET_REG, val,
> +					(val & SOFT_RESET_BIT) == 0,
> +					1, 100);
> +}
> +
> +static const struct reset_control_ops sparx5_reset_ops = {
> +	.reset = sparx5_switch_reset,
> +};
> +
> +static int mchp_sparx5_map_syscon(struct platform_device *pdev, char *name,
> +				  struct regmap **target)
> +{
> +	struct device_node *syscon_np;
> +	struct regmap *regmap;
> +	int err;
> +
> +	syscon_np = of_parse_phandle(pdev->dev.of_node, name, 0);
> +	if (!syscon_np)
> +		return -ENODEV;
> +	regmap = syscon_node_to_regmap(syscon_np);
> +	of_node_put(syscon_np);
> +	if (IS_ERR(regmap)) {
> +		err = PTR_ERR(regmap);
> +		dev_err(&pdev->dev, "No '%s' map: %d\n", name, err);
> +		return err;
> +	}
> +	*target = regmap;
> +	return 0;
> +}
> +
> +static int mchp_sparx5_map_io(struct platform_device *pdev, int index,
> +			      struct regmap **target)
> +{
> +	struct resource *res;
> +	struct regmap *map;
> +	void __iomem *mem;
> +
> +	mem = devm_platform_get_and_ioremap_resource(pdev, index, &res);
> +	if (!mem) {
> +		dev_err(&pdev->dev, "Could not map resource %d\n", index);
> +		return -ENXIO;
> +	}
> +	sparx5_reset_regmap_config.name = res->name;
> +	map = devm_regmap_init_mmio(&pdev->dev, mem, &sparx5_reset_regmap_config);
> +	if (IS_ERR(map))
> +		return PTR_ERR(map);
> +	*target = map;
> +	return 0;
> +}
> +
> +static int mchp_sparx5_reset_probe(struct platform_device *pdev)
> +{
> +	struct device_node *dn = pdev->dev.of_node;
> +	struct mchp_reset_context *ctx;
> +	int err;
> +
> +	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	err = mchp_sparx5_map_syscon(pdev, "cpu-syscon", &ctx->cpu_ctrl);
> +	if (err)
> +		return err;
> +	err = mchp_sparx5_map_io(pdev, 0, &ctx->gcb_ctrl);
> +	if (err)
> +		return err;
> +
> +	ctx->rcdev.owner = THIS_MODULE;
> +	ctx->rcdev.nr_resets = 1;
> +	ctx->rcdev.ops = &sparx5_reset_ops;
> +	ctx->rcdev.of_node = dn;
> +
> +	return devm_reset_controller_register(&pdev->dev, &ctx->rcdev);
> +}
> +
> +static const struct of_device_id mchp_sparx5_reset_of_match[] = {
> +	{
> +		.compatible = "microchip,sparx5-switch-reset",
> +	},
> +	{ }
> +};
> +
> +static struct platform_driver mchp_sparx5_reset_driver = {
> +	.probe = mchp_sparx5_reset_probe,
> +	.driver = {
> +		.name = "sparx5-switch-reset",
> +		.of_match_table = mchp_sparx5_reset_of_match,
> +	},
> +};
> +
> +static int __init mchp_sparx5_reset_init(void)
> +{
> +	return platform_driver_register(&mchp_sparx5_reset_driver);
> +}
> +
> +postcore_initcall(mchp_sparx5_reset_init);
> +
> +MODULE_DESCRIPTION("Microchip Sparx5 switch reset driver");
> +MODULE_AUTHOR("Steen Hegelund <steen.hegelund@microchip.com>");
> +MODULE_LICENSE("Dual MIT/GPL");
> -- 
> 2.30.1
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com