Re: [PATCH 6/8] power: reset: at91-reset: add reset_controller_dev support

[Philipp Zabel <p.zabel@pengutronix.de>]

Hi Claudiu,

On Di, 2022-04-05 at 14:27 +0300, Claudiu Beznea wrote:
> SAMA7G5 reset controller has 5 extra lines that goes to different
> devices
> (3 lines to USB PHYs, 1 line to DDR controller, one line DDR PHY
> controller). These reset lines could be requested by different
> controller
> drivers (e.g. USB PHY driver) and these controllers' drivers could
> assert/deassert these lines when necessary. Thus add support for
> reset_controller_dev which brings this functionality.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
>  drivers/power/reset/at91-reset.c | 92
> ++++++++++++++++++++++++++++++--
>  1 file changed, 88 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/power/reset/at91-reset.c
> b/drivers/power/reset/at91-reset.c
> index 0d721e27f545..b04df54c15d2 100644
> --- a/drivers/power/reset/at91-reset.c
> +++ b/drivers/power/reset/at91-reset.c
> @@ -17,6 +17,7 @@
>  #include <linux/of_address.h>
>  #include <linux/platform_device.h>
>  #include <linux/reboot.h>
> +#include <linux/reset-controller.h>
>  
>  #include <soc/at91/at91sam9_ddrsdr.h>
>  #include <soc/at91/at91sam9_sdramc.h>
> @@ -53,12 +54,16 @@ enum reset_type {
>  struct at91_reset {
>         void __iomem *rstc_base;
>         void __iomem *ramc_base[2];
> +       void __iomem *dev_base;
> +       struct reset_controller_dev rcdev;
>         struct clk *sclk;
>         struct notifier_block nb;
>         u32 args;
>         u32 ramc_lpr;
>  };
>  
> +#define to_at91_reset(r)       container_of(r, struct at91_reset, rcdev)
> +
>  struct at91_reset_data {
>         u32 reset_args;
>         u32 n_device_reset;
> @@ -191,6 +196,79 @@ static const struct of_device_id
> at91_reset_of_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, at91_reset_of_match);
>  
> +static int at91_reset_update(struct reset_controller_dev *rcdev,
> +                            unsigned long id, bool assert)
> +{
> +       struct at91_reset *reset = to_at91_reset(rcdev);
> +       u32 val;
> +
> +       val = readl_relaxed(reset->dev_base);
> +       if (assert)
> +               val |= BIT(id);
> +       else
> +               val &= ~BIT(id);
> +       writel_relaxed(val, reset->dev_base);

This read-modify-update should be protected by a spinlock.

> +
> +       return 0;
> +}
> +
> +static int at91_reset_assert(struct reset_controller_dev *rcdev,
> +                            unsigned long id)
> +{
> +       return at91_reset_update(rcdev, id, true);
> +}
> +
> +static int at91_reset_deassert(struct reset_controller_dev *rcdev,
> +                              unsigned long id)
> +{
> +       return at91_reset_update(rcdev, id, false);
> +}
> +
> +static int at91_reset_dev_status(struct reset_controller_dev *rcdev,
> +                                unsigned long id)
> +{
> +       struct at91_reset *reset = to_at91_reset(rcdev);
> +       u32 val;
> +
> +       val = readl_relaxed(reset->dev_base);
> +
> +       return !!(val & BIT(id));
> +}
> +
> +static const struct reset_control_ops at91_reset_ops = {
> +       .assert = at91_reset_assert,
> +       .deassert = at91_reset_deassert,
> +       .status = at91_reset_dev_status,
> +};
> +
> +static int at91_reset_of_xlate(struct reset_controller_dev *rcdev,
> +                              const struct of_phandle_args *reset_spec)
> +{
> +       return reset_spec->args[0];
> +}

For 1:1 mappings there is no need for a custom of_xlate handler. Just
leave of_xlate and of_reset_n_cells empty.

> +
> +static int at91_rcdev_init(struct at91_reset *reset,
> +                          const struct at91_reset_data *data,
> +                          struct platform_device *pdev)
> +{
> +       if (!data->n_device_reset)
> +               return 0;
> +
> +       reset->dev_base = devm_of_iomap(&pdev->dev, pdev->dev.of_node, 1,
> +                                       NULL);
> +       if (IS_ERR(reset->rstc_base))

Should check reset->dev_base here.

> +               return -ENODEV;
> +
> +       reset->rcdev.ops = &at91_reset_ops;
> +       reset->rcdev.owner = THIS_MODULE;
> +       reset->rcdev.of_node = pdev->dev.of_node;
> +       reset->rcdev.nr_resets = data->n_device_reset;
> +       reset->rcdev.of_reset_n_cells = 1;
> +       reset->rcdev.of_xlate = at91_reset_of_xlate;
> +
> +       return devm_reset_controller_register(&pdev->dev, &reset->rcdev);
> +}
> +
>  static int __init at91_reset_probe(struct platform_device *pdev)
>  {
>         const struct of_device_id *match;
> @@ -244,6 +322,10 @@ static int __init at91_reset_probe(struct
> platform_device *pdev)
>  
>         platform_set_drvdata(pdev, reset);
>  
> +       ret = at91_rcdev_init(reset, data, pdev);
> +       if (ret)
> +               goto disable_clk;
> +
>         if (of_device_is_compatible(pdev->dev.of_node,
> "microchip,sam9x60-rstc")) {
>                 u32 val = readl(reset->rstc_base + AT91_RSTC_MR);
>  
> @@ -252,14 +334,16 @@ static int __init at91_reset_probe(struct
> platform_device *pdev)
>         }
>  
>         ret = register_restart_handler(&reset->nb);
> -       if (ret) {
> -               clk_disable_unprepare(reset->sclk);
> -               return ret;
> -       }
> +       if (ret)
> +               goto disable_clk;
>  
>         at91_reset_status(pdev, reset->rstc_base);
>  
>         return 0;
> +
> +disable_clk:
> +       clk_disable_unprepare(reset->sclk);
> +       return ret;
>  }
>  
>  static int __exit at91_reset_remove(struct platform_device *pdev)

regards
Philipp