On Thu, Feb 16, 2017 at 12:23:18PM -0500, Chris Brandt wrote:
> Some Renesas SoCs do not have a reset register and the only way to do a SW
> controlled reset is to use the watchdog timer. Additionally, since all the
> WDT timeout options are so quick, a system reset is about the only thing
> it's good for.
>
> Signed-off-by: Chris Brandt <chris.brandt@xxxxxxxxxxx>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Wondering - why not use the watchdog driver and the infrastructure
provided by the watchdog core (ie the restart callback) instead ?
> ---
> v2:
> * changed DT bindings from 'wdt-reset' to 'rza-wdt'
> * changed hard coded register values to defines
> * added msleep to while(1) loop
Sure you can sleep here ?
Guenter
> * removed unnecessary #include files
> * added Reviewed-by: Geert Uytterhoeven
> ---
> drivers/power/reset/Kconfig | 9 +++
> drivers/power/reset/Makefile | 1 +
> drivers/power/reset/renesas-reset.c | 112 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 122 insertions(+)
> create mode 100644 drivers/power/reset/renesas-reset.c
>
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index b8caccc..e3100c9 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -130,6 +130,15 @@ config POWER_RESET_QNAP
>
> Say Y if you have a QNAP NAS.
>
> +config POWER_RESET_RENESAS
> + tristate "Renesas WDT reset driver"
> + depends on ARCH_RENESAS || COMPILE_TEST
> + depends on HAS_IOMEM
> + help
> + Reboot support for Renesas SoCs with WDT reset.
> + Some Renesas SoCs do not have a reset register and the only way
> + to do a SW controlled reset is to use the watchdog timer.
> +
> config POWER_RESET_RESTART
> bool "Restart power-off driver"
> help
> diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
> index 11dae3b..a78a56c 100644
> --- a/drivers/power/reset/Makefile
> +++ b/drivers/power/reset/Makefile
> @@ -13,6 +13,7 @@ obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
> obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o
> obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
> obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
> +obj-$(CONFIG_POWER_RESET_RENESAS) += renesas-reset.o
> obj-$(CONFIG_POWER_RESET_RESTART) += restart-poweroff.o
> obj-$(CONFIG_POWER_RESET_ST) += st-poweroff.o
> obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o
> diff --git a/drivers/power/reset/renesas-reset.c b/drivers/power/reset/renesas-reset.c
> new file mode 100644
> index 0000000..812cee0
> --- /dev/null
> +++ b/drivers/power/reset/renesas-reset.c
> @@ -0,0 +1,112 @@
> +/*
> + * Renesas WDT Reset Driver
> + *
> + * Copyright (C) 2017 Renesas Electronics America, Inc.
> + * Copyright (C) 2017 Chris Brandt
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *
> + * based on rmobile-reset.c
> + *
> + */
> +
> +#include <linux/platform_device.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/reboot.h>
> +#include <linux/delay.h>
> +
> +/* Watchdog Timer Registers */
> +#define WTCSR 0
> +#define WTCSR_MAGIC 0xA500
> +#define WTSCR_WT (1<<6)
> +#define WTSCR_TME (1<<5)
> +
> +#define WTCNT 2
> +#define WTCNT_MAGIC 0x5A00
> +
> +#define WRCSR 4
> +#define WRCSR_MAGIC 0x5A00
> +#define WRCSR_RSTE (1<<6)
> +#define WRCSR_CLEAR_WOVF 0xA500 /* special value */
> +
> +static void __iomem *base;
> +
> +static int wdt_reset_handler(struct notifier_block *this,
> + unsigned long mode, void *cmd)
> +{
> + pr_debug("%s %lu\n", __func__, mode);
> +
> + /* Dummy read (must read WRCSR:WOVF at least once before clearing) */
> + readb(base + WRCSR);
> +
> + writew(WRCSR_CLEAR_WOVF, base + WRCSR); /* Clear WOVF */
> + writew(WRCSR_MAGIC | WRCSR_RSTE, base + WRCSR); /* Reset Enable */
> + writew(WTCNT_MAGIC, base + WTCNT); /* Counter to 00 */
> +
> + /* Start timer */
> + writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, base + WTCSR);
> +
> + /* Wait for WDT overflow (reset) */
> + while (1)
> + msleep(1);
> +
> + return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block wdt_reset_nb = {
> + .notifier_call = wdt_reset_handler,
> + .priority = 192,
> +};
> +
> +static int wdt_reset_probe(struct platform_device *pdev)
> +{
> + int error;
> +
> + base = of_iomap(pdev->dev.of_node, 0);
> + if (!base)
> + return -ENODEV;
> +
> + error = register_restart_handler(&wdt_reset_nb);
> + if (error) {
> + dev_err(&pdev->dev,
> + "cannot register restart handler (err=%d)\n", error);
> + goto fail_unmap;
> + }
> +
> + return 0;
> +
> +fail_unmap:
> + iounmap(base);
> + return error;
> +}
> +
> +static int wdt_reset_remove(struct platform_device *pdev)
> +{
> + unregister_restart_handler(&wdt_reset_nb);
> + iounmap(base);
> + return 0;
> +}
> +
> +static const struct of_device_id wdt_reset_of_match[] = {
> + { .compatible = "renesas,rza-wdt", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, wdt_reset_of_match);
> +
> +static struct platform_driver wdt_reset_driver = {
> + .probe = wdt_reset_probe,
> + .remove = wdt_reset_remove,
> + .driver = {
> + .name = "wdt_reset",
> + .of_match_table = wdt_reset_of_match,
> + },
> +};
> +
> +module_platform_driver(wdt_reset_driver);
> +
> +MODULE_DESCRIPTION("Renesas WDT Reset Driver");
> +MODULE_AUTHOR("Chris Brandt <chris.brandt@xxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");
> --
> 2.10.1
>
>
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