linux-kernel - Re: [PATCH v4] drivers/soc/litex: Add restart handler

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Date:   Wed, 20 Jan 2021 21:46:13 +0000
From:   Joel Stanley <joel@....id.au>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Stafford Horne <shorne@...il.com>,
        Karol Gugala <kgugala@...micro.com>,
        Mateusz Holenko <mholenko@...micro.com>,
        Gabriel Somlo <gsomlo@...il.com>,
        linux-riscv@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] drivers/soc/litex: Add restart handler

On Tue, 19 Jan 2021 at 08:14, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Let the LiteX SoC Controller register a restart handler, which resets
> the LiteX SoC by writing 1 to CSR_CTRL_RESET_ADDR.
>
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Reviewed-by: Joel Stanley <joel@....id.au>

> ---
> v4:
>   - Drop bogus "a" from description,
>   - Get rid of static litex_soc_ctrl_device and litex_reset_nb
>     instances,
>   - Unregister handler on driver unbind,
>
> v3:
>   - Rebase on top of openrisc/for-next,
>
> v2:
>   - Rebase on top of v5.11-rc1,
>   - Change reset handler priority to recommended default value of 128
>     (was 192).
>
> (v1 was not sent to a mailing list)
> ---
>  drivers/soc/litex/litex_soc_ctrl.c | 42 +++++++++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/soc/litex/litex_soc_ctrl.c b/drivers/soc/litex/litex_soc_ctrl.c
> index da17ba56b7956c84..a7dd5be9fd5bd8ad 100644
> --- a/drivers/soc/litex/litex_soc_ctrl.c
> +++ b/drivers/soc/litex/litex_soc_ctrl.c
> @@ -15,6 +15,11 @@
>  #include <linux/module.h>
>  #include <linux/errno.h>
>  #include <linux/io.h>
> +#include <linux/reboot.h>
> +
> +/* reset register located at the base address */
> +#define RESET_REG_OFF           0x00
> +#define RESET_REG_VALUE         0x00000001
>
>  #define SCRATCH_REG_OFF         0x04
>  #define SCRATCH_REG_VALUE       0x12345678
> @@ -66,8 +71,19 @@ static int litex_check_csr_access(void __iomem *reg_addr)
>
>  struct litex_soc_ctrl_device {
>         void __iomem *base;
> +       struct notifier_block reset_nb;
>  };
>
> +static int litex_reset_handler(struct notifier_block *this, unsigned long mode,
> +                              void *cmd)
> +{
> +       struct litex_soc_ctrl_device *soc_ctrl_dev =
> +               container_of(this, struct litex_soc_ctrl_device, reset_nb);
> +
> +       litex_write32(soc_ctrl_dev->base + RESET_REG_OFF, RESET_REG_VALUE);
> +       return NOTIFY_DONE;
> +}
> +
>  static const struct of_device_id litex_soc_ctrl_of_match[] = {
>         {.compatible = "litex,soc-controller"},
>         {},
> @@ -78,6 +94,7 @@ MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
>  static int litex_soc_ctrl_probe(struct platform_device *pdev)
>  {
>         struct litex_soc_ctrl_device *soc_ctrl_dev;
> +       int error;
>
>         soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
>         if (!soc_ctrl_dev)
> @@ -87,7 +104,29 @@ static int litex_soc_ctrl_probe(struct platform_device *pdev)
>         if (IS_ERR(soc_ctrl_dev->base))
>                 return PTR_ERR(soc_ctrl_dev->base);
>
> -       return litex_check_csr_access(soc_ctrl_dev->base);
> +       error = litex_check_csr_access(soc_ctrl_dev->base);
> +       if (error)
> +               return error;
> +
> +       platform_set_drvdata(pdev, soc_ctrl_dev);
> +
> +       soc_ctrl_dev->reset_nb.notifier_call = litex_reset_handler;
> +       soc_ctrl_dev->reset_nb.priority = 128;
> +       error = register_restart_handler(&soc_ctrl_dev->reset_nb);
> +       if (error) {
> +               dev_warn(&pdev->dev, "cannot register restart handler: %d\n",
> +                        error);
> +       }
> +
> +       return 0;
> +}
> +
> +static int litex_soc_ctrl_remove(struct platform_device *pdev)
> +{
> +       struct litex_soc_ctrl_device *soc_ctrl_dev = platform_get_drvdata(pdev);
> +
> +       unregister_restart_handler(&soc_ctrl_dev->reset_nb);
> +       return 0;
>  }
>
>  static struct platform_driver litex_soc_ctrl_driver = {
> @@ -96,6 +135,7 @@ static struct platform_driver litex_soc_ctrl_driver = {
>                 .of_match_table = of_match_ptr(litex_soc_ctrl_of_match)
>         },
>         .probe = litex_soc_ctrl_probe,
> +       .remove = litex_soc_ctrl_remove,
>  };
>
>  module_platform_driver(litex_soc_ctrl_driver);
> --
> 2.25.1
>