[U-Boot] [PATCH] sysreset: Add support for gpio-restart

[Simon Glass]

Hi Michal,

On 13 July 2018 at 03:15, Michal Simek <michal.simek at xilinx.com> wrote:
> The Linux kernel has binding for gpio-restart node.
> This patch is adding basic support without supporting any optional
> properties.
> This driver was tested on Microblaze system where gpio is connected to
> SoC reset logic.
> Output value is handled via gpios cells values.
>
> In gpio_reboot_request() set_value is writing 1 because
> dm_gpio_set_value() is capable to changing it when it is ACTIVE_LOW.
> ...
>         if (desc->flags & GPIOD_ACTIVE_LOW)
>                 value = !value;
> ...
>
> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> ---
>
>  drivers/sysreset/Kconfig         |  6 ++++
>  drivers/sysreset/Makefile        |  1 +
>  drivers/sysreset/sysreset_gpio.c | 59 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 66 insertions(+)
>  create mode 100644 drivers/sysreset/sysreset_gpio.c

Reviewed-by: Simon Glass <sjg at chromium.org>

But please see below.

>
> diff --git a/drivers/sysreset/Kconfig b/drivers/sysreset/Kconfig
> index a6d48e8a662c..1e228b97443a 100644
> --- a/drivers/sysreset/Kconfig
> +++ b/drivers/sysreset/Kconfig
> @@ -15,6 +15,12 @@ config SYSRESET
>
>  if SYSRESET
>
> +config SYSRESET_GPIO
> +       bool "Enable support for GPIO restart driver"
> +       select GPIO
> +       help
> +         Restart support via GPIO pin connected reset logic.

What does this mean? Please expand this to explain what it means.

Also, what is the difference between restart and reset? If there is no
difference please use the word 'reset'. If there is a difference,
please explain it here.

> +
>  config SYSRESET_PSCI
>         bool "Enable support for PSCI System Reset"
>         depends on ARM_PSCI_FW
> diff --git a/drivers/sysreset/Makefile b/drivers/sysreset/Makefile
> index 0da58a1cf6ad..ca533cfefaad 100644
> --- a/drivers/sysreset/Makefile
> +++ b/drivers/sysreset/Makefile
> @@ -3,6 +3,7 @@
>  # (C) Copyright 2016 Cadence Design Systems Inc.
>
>  obj-$(CONFIG_SYSRESET) += sysreset-uclass.o
> +obj-$(CONFIG_SYSRESET_GPIO) += sysreset_gpio.o
>  obj-$(CONFIG_SYSRESET_PSCI) += sysreset_psci.o
>  obj-$(CONFIG_SYSRESET_SYSCON) += sysreset_syscon.o
>  obj-$(CONFIG_SYSRESET_WATCHDOG) += sysreset_watchdog.o
> diff --git a/drivers/sysreset/sysreset_gpio.c b/drivers/sysreset/sysreset_gpio.c
> new file mode 100644
> index 000000000000..4c1c1510f285
> --- /dev/null
> +++ b/drivers/sysreset/sysreset_gpio.c
> @@ -0,0 +1,59 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2018 Xilinx, Inc. - Michal Simek
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <errno.h>
> +#include <sysreset.h>
> +#include <asm/gpio.h>
> +
> +struct gpio_reboot_priv {
> +       struct gpio_desc gpio;
> +};
> +
> +static int gpio_reboot_request(struct udevice *dev, enum sysreset_t type)
> +{
> +       struct gpio_reboot_priv *priv = dev_get_priv(dev);
> +
> +       /*
> +        * When debug log is enabled please make sure that chars won't end up
> +        * in output fifo. Or you can append udelay(); to get enough time
> +        * to HW to emit output fifo.
> +        */
> +       debug("GPIO restart\n");
> +
> +       /* 1 is just setting value - based on gpio->flags 0 or 1 is written */

Do you mean that it respects polarity (active high/low)? If so, it
might be less confusing to state that.

> +       return dm_gpio_set_value(&priv->gpio, 1);
> +}
> +
> +static struct sysreset_ops gpio_reboot_ops = {
> +       .request = gpio_reboot_request,
> +};
> +
> +int gpio_reboot_probe(struct udevice *dev)
> +{
> +       struct gpio_reboot_priv *priv = dev_get_priv(dev);
> +
> +       /*
> +        * Linux kernel DT binding contain others optional properties
> +        * which are not supported now
> +        */
> +
> +       return gpio_request_by_name(dev, "gpios", 0, &priv->gpio, GPIOD_IS_OUT);
> +}
> +
> +static const struct udevice_id led_gpio_ids[] = {
> +       { .compatible = "gpio-restart" },
> +       { }
> +};
> +
> +U_BOOT_DRIVER(gpio_reboot) = {
> +       .id = UCLASS_SYSRESET,
> +       .name = "gpio_restart",
> +       .of_match = led_gpio_ids,
> +       .ops = &gpio_reboot_ops,
> +       .priv_auto_alloc_size = sizeof(struct gpio_reboot_priv),
> +       .probe = gpio_reboot_probe,
> +};
> --
> 1.9.1
>

Regards,
Simon