[PATCH v3 15/21] reset: add driver for generic reset controllers

[Manivannan Sadhasivam]

On Sat, Jan 25, 2020 at 05:52:57PM +0530, Amit Singh Tomar wrote:
> The simplest and most generic form of a reset controller just exposes
> multiple MMIO registers, where each bit toggles a separate reset line.
> Add a generic driver to describe this kind of reset controller.
> 
> This is used on the Action Semi S700, for instance, but also by other
> SoCs.
> 

Why not name it as reset-simple as linux kernel?

> Signed-off-by: Amit Singh Tomar <amittomer25 at gmail.com>
> [Andre: make more generic, let it cover multiple registers, slight rework]
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
> Changes since v2:
>         * Newly added patch, not there in v2/v1.
> ---
>  drivers/reset/Kconfig         |   6 +++
>  drivers/reset/Makefile        |   1 +
>  drivers/reset/reset-generic.c | 111 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 118 insertions(+)
>  create mode 100644 drivers/reset/reset-generic.c
> 
> diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
> index 75ccd65..1cdc159 100644
> --- a/drivers/reset/Kconfig
> +++ b/drivers/reset/Kconfig
> @@ -12,6 +12,12 @@ config DM_RESET
>  	  although driving such reset isgnals using GPIOs may be more
>  	  appropriate in this case.
>  
> +config GENERIC_RESET
> +        bool "Generic Reset controller driver"
> +        depends on DM_RESET
> +        help
> +          Support Generic reset controller.
> +
>  config SANDBOX_RESET
>  	bool "Enable the sandbox reset test driver"
>  	depends on DM_MAILBOX && SANDBOX
> diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
> index 0a044d5..5e027a1 100644
> --- a/drivers/reset/Makefile
> +++ b/drivers/reset/Makefile
> @@ -4,6 +4,7 @@
>  #
>  
>  obj-$(CONFIG_DM_RESET) += reset-uclass.o
> +obj-$(CONFIG_GENERIC_RESET) += reset-generic.o
>  obj-$(CONFIG_SANDBOX_MBOX) += sandbox-reset.o
>  obj-$(CONFIG_SANDBOX_MBOX) += sandbox-reset-test.o
>  obj-$(CONFIG_STI_RESET) += sti-reset.o
> diff --git a/drivers/reset/reset-generic.c b/drivers/reset/reset-generic.c
> new file mode 100644
> index 0000000..9c45087
> --- /dev/null
> +++ b/drivers/reset/reset-generic.c
> @@ -0,0 +1,111 @@
> +/*
> + * Copyright (C) 2017 Amit Singh Tomar <amittomer25 at gmail.com>
> + *
> + * SPDX-License-Identifier:	GPL-2.0+
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <errno.h>
> +#include <reset-uclass.h>
> +#include <linux/bitops.h>
> +#include <linux/io.h>
> +#include <linux/sizes.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +struct generic_reset_priv {
> +	void __iomem *membase;
> +	int max_reset;
> +};
> +
> +#define BITS_PER_BYTE 8
> +static int generic_reset_toggle(struct reset_ctl *rst, bool assert)
> +{
> +	struct generic_reset_priv *priv = dev_get_priv(rst->dev);
> +	int reg_width = sizeof(u32);
> +	int bank, offset;
> +	u32 reg;
> +
> +	if (rst->id >= priv->max_reset)
> +		return -EINVAL;
> +
> +	bank = rst->id / (reg_width * BITS_PER_BYTE);
> +	offset = rst->id % (reg_width * BITS_PER_BYTE);
> +
> +	reg = readl(priv->membase + (bank * reg_width));
> +	if (assert)
> +		writel(reg & ~BIT(offset), priv->membase + (bank * reg_width));
> +	else
> +		writel(reg | BIT(offset), priv->membase + (bank * reg_width));
> +
> +	return 0;
> +}
> +
> +static int generic_reset_assert(struct reset_ctl *rst)
> +{
> +	return generic_reset_toggle(rst, true);
> +}
> +
> +static int generic_reset_deassert(struct reset_ctl *rst)
> +{
> +	return generic_reset_toggle(rst, false);
> +}
> +
> +static int generic_reset_free(struct reset_ctl *rst)
> +{
> +	return 0;
> +}
> +
> +static int generic_reset_request(struct reset_ctl *rst)
> +{
> +	struct generic_reset_priv *priv = dev_get_priv(rst->dev);
> +
> +	if (rst->id >= priv->max_reset)
> +		return -EINVAL;
> +
> +	return generic_reset_assert(rst);
> +}
> +
> +struct reset_ops generic_reset_reset_ops = {
> +	.free = generic_reset_free,
> +	.request = generic_reset_request,
> +	.rst_assert = generic_reset_assert,
> +	.rst_deassert = generic_reset_deassert,
> +};
> +
> +static const struct udevice_id generic_reset_ids[] = {
> +	{ .compatible = "generic-reset" },
> +	{ .compatible = "actions,s700-reset" },

No need of S700 specific compatible here. Linux kernel dts also doesn't
require it.

Thanks,
Mani

> +	{ }
> +};
> +
> +static int generic_reset_probe(struct udevice *dev)
> +{
> +	struct generic_reset_priv *priv = dev_get_priv(dev);
> +	fdt_addr_t addr;
> +	fdt_size_t size;
> +
> +	addr = devfdt_get_addr_size_index(dev, 0, &size);
> +	if (addr == FDT_ADDR_T_NONE)
> +		return -EINVAL;
> +
> +	priv->max_reset = dev_read_u32_default(dev, "num-resets", -1);
> +	if (priv->max_reset == -1)
> +		priv->max_reset = size * BITS_PER_BYTE;
> +
> +	priv->membase = devm_ioremap(dev, addr, size);
> +	if (!priv->membase)
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
> +U_BOOT_DRIVER(generic_reset) = {
> +	.name = "generic_reset",
> +	.id = UCLASS_RESET,
> +	.of_match = generic_reset_ids,
> +	.ops = &generic_reset_reset_ops,
> +	.probe = generic_reset_probe,
> +	.priv_auto_alloc_size = sizeof(struct generic_reset_priv),
> +};
> -- 
> 2.7.4
>