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Date:   Tue, 12 Apr 2022 23:39:50 +0100
From:   Paul Cercueil <paul@crapouillou.net>
Subject: Re: [PATCH v5 2/2] clk: ingenic-tcu: Fix missing TCU clock for X1000
 SoCs
To:     Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Cc:     robh+dt@kernel.org, krzk+dt@kernel.org, tsbogend@alpha.franken.de,
        mturquette@baylibre.com, sboyd@kernel.org,
        linux-mips@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
        dan.carpenter@oracle.com
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        <20220412122750.279058-3-aidanmacdonald.0x0@gmail.com>
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Hi,

Le mar., avril 12 2022 at 13:27:50 +0100, Aidan MacDonald=20
<aidanmacdonald.0x0@gmail.com> a =E9crit :
> The TCU clock gate on X1000 wasn't requested by the driver and could
> be gated automatically later on in boot, which prevents timers from
> running and breaks PWM.
>=20
> Add a workaround to support old device trees that don't specify the
> "tcu" clock gate. In this case the kernel will print a warning and
> attempt to continue without the clock, which is wrong, but it could
> work if "clk_ignore_unused" is in the kernel arguments.
>=20
> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>

Reviewed-by: Paul Cercueil <paul@crapouillou.net>

Cheers,
-Paul

> ---
>  drivers/clk/ingenic/tcu.c | 35 +++++++++++++++++++++++++----------
>  1 file changed, 25 insertions(+), 10 deletions(-)
>=20
> diff --git a/drivers/clk/ingenic/tcu.c b/drivers/clk/ingenic/tcu.c
> index 77acfbeb4830..201bf6e6b6e0 100644
> --- a/drivers/clk/ingenic/tcu.c
> +++ b/drivers/clk/ingenic/tcu.c
> @@ -31,6 +31,7 @@ struct ingenic_soc_info {
>  	unsigned int num_channels;
>  	bool has_ost;
>  	bool has_tcu_clk;
> +	bool allow_missing_tcu_clk;
>  };
>=20
>  struct ingenic_tcu_clk_info {
> @@ -320,7 +321,8 @@ static const struct ingenic_soc_info=20
> jz4770_soc_info =3D {
>  static const struct ingenic_soc_info x1000_soc_info =3D {
>  	.num_channels =3D 8,
>  	.has_ost =3D false, /* X1000 has OST, but it not belong TCU */
> -	.has_tcu_clk =3D false,
> +	.has_tcu_clk =3D true,
> +	.allow_missing_tcu_clk =3D true,
>  };
>=20
>  static const struct of_device_id __maybe_unused=20
> ingenic_tcu_of_match[] __initconst =3D {
> @@ -355,14 +357,27 @@ static int __init ingenic_tcu_probe(struct=20
> device_node *np)
>  		tcu->clk =3D of_clk_get_by_name(np, "tcu");
>  		if (IS_ERR(tcu->clk)) {
>  			ret =3D PTR_ERR(tcu->clk);
> -			pr_crit("Cannot get TCU clock\n");
> -			goto err_free_tcu;
> -		}
>=20
> -		ret =3D clk_prepare_enable(tcu->clk);
> -		if (ret) {
> -			pr_crit("Unable to enable TCU clock\n");
> -			goto err_put_clk;
> +			/*
> +			 * Old device trees for some SoCs did not include the
> +			 * TCU clock because this driver (incorrectly) didn't
> +			 * use it. In this case we complain loudly and attempt
> +			 * to continue without the clock, which might work if
> +			 * booting with workarounds like "clk_ignore_unused".
> +			 */
> +			if (tcu->soc_info->allow_missing_tcu_clk && ret =3D=3D -EINVAL) {
> +				pr_warn("TCU clock missing from device tree, please update your=20
> device tree\n");
> +				tcu->clk =3D NULL;
> +			} else {
> +				pr_crit("Cannot get TCU clock from device tree\n");
> +				goto err_free_tcu;
> +			}
> +		} else {
> +			ret =3D clk_prepare_enable(tcu->clk);
> +			if (ret) {
> +				pr_crit("Unable to enable TCU clock\n");
> +				goto err_put_clk;
> +			}
>  		}
>  	}
>=20
> @@ -432,10 +447,10 @@ static int __init ingenic_tcu_probe(struct=20
> device_node *np)
>  			clk_hw_unregister(tcu->clocks->hws[i]);
>  	kfree(tcu->clocks);
>  err_clk_disable:
> -	if (tcu->soc_info->has_tcu_clk)
> +	if (tcu->clk)
>  		clk_disable_unprepare(tcu->clk);
>  err_put_clk:
> -	if (tcu->soc_info->has_tcu_clk)
> +	if (tcu->clk)
>  		clk_put(tcu->clk);
>  err_free_tcu:
>  	kfree(tcu);
> --
> 2.35.1
>=20