linux-kernel - Re: [PATCH 1/3] reset: microchip-sparx5: issue a reset on startup

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Date:   Mon, 29 Aug 2022 11:14:18 +0200
From:   Steen Hegelund <steen.hegelund@...rochip.com>
To:     Michael Walle <michael@...le.cc>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Philipp Zabel <p.zabel@...gutronix.de>
CC:     <UNGLinuxDriver@...rochip.com>, <netdev@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] reset: microchip-sparx5: issue a reset on startup

Hi Michael,

On Fri, 2022-08-26 at 13:56 +0200, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Originally this was used in by the switch core driver to issue a reset.
> But it turns out, this isn't just a switch core reset but instead it
> will reset almost the complete SoC.
> 
> Instead of adding almost all devices of the SoC a shared reset line,
> issue the reset once early on startup. Keep the reset controller for
> backwards compatibility, but make the actual reset a noop.
> 
> Suggested-by: Philipp Zabel <p.zabel@...gutronix.de>
> Signed-off-by: Michael Walle <michael@...le.cc>
> ---
>  drivers/reset/reset-microchip-sparx5.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/reset/reset-microchip-sparx5.c b/drivers/reset/reset-microchip-sparx5.c
> index 00b612a0effa..f3528dd1d084 100644
> --- a/drivers/reset/reset-microchip-sparx5.c
> +++ b/drivers/reset/reset-microchip-sparx5.c
> @@ -33,11 +33,8 @@ static struct regmap_config sparx5_reset_regmap_config = {
>         .reg_stride     = 4,
>  };
> 
> -static int sparx5_switch_reset(struct reset_controller_dev *rcdev,
> -                              unsigned long id)
> +static int sparx5_switch_reset(struct mchp_reset_context *ctx)
>  {
> -       struct mchp_reset_context *ctx =
> -               container_of(rcdev, struct mchp_reset_context, rcdev);
>         u32 val;
> 
>         /* Make sure the core is PROTECTED from reset */
> @@ -54,8 +51,14 @@ static int sparx5_switch_reset(struct reset_controller_dev *rcdev,
>                                         1, 100);
>  }
> 
> +static int sparx5_reset_noop(struct reset_controller_dev *rcdev,
> +                            unsigned long id)
> +{
> +       return 0;
> +}
> +
>  static const struct reset_control_ops sparx5_reset_ops = {
> -       .reset = sparx5_switch_reset,
> +       .reset = sparx5_reset_noop,
>  };
> 
>  static int mchp_sparx5_map_syscon(struct platform_device *pdev, char *name,
> @@ -122,6 +125,11 @@ static int mchp_sparx5_reset_probe(struct platform_device *pdev)
>         ctx->rcdev.of_node = dn;
>         ctx->props = device_get_match_data(&pdev->dev);
> 
> +       /* Issue the reset very early, our actual reset callback is a noop. */
> +       err = sparx5_switch_reset(ctx);
> +       if (err)
> +               return err;
> +
>         return devm_reset_controller_register(&pdev->dev, &ctx->rcdev);
>  }
> 
> @@ -163,6 +171,10 @@ static int __init mchp_sparx5_reset_init(void)
>         return platform_driver_register(&mchp_sparx5_reset_driver);
>  }
> 
> +/*
> + * Because this is a global reset, keep this postcore_initcall() to issue the
> + * reset as early as possible during the kernel startup.
> + */
>  postcore_initcall(mchp_sparx5_reset_init);
> 
>  MODULE_DESCRIPTION("Microchip Sparx5 switch reset driver");
> --
> 2.30.2
> 

Tested-by: Steen Hegelund <Steen.Hegelund@...rochip.com> on Sparx5

BR
Steen