linux-kernel - Re: [PATCH v3 5/6] clk: samsung: Extract parent clock enabling to common function

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Date:   Mon, 6 Mar 2023 15:35:06 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     Tomasz Figa <tomasz.figa@...il.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Chanho Park <chanho61.park@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/6] clk: samsung: Extract parent clock enabling to
 common function

On 23/02/2023 05:19, Sam Protsenko wrote:
> Extract parent clock enabling from exynos_arm64_register_cmu() to
> dedicated function.
> 
> Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
> Changes in v3:
>   - Rebased on top of latest soc/for-next tree
>   - Added Marek's Acked-by tag
> 
> Changes in v2:
>   - Rebased on top of latest soc/for-next tree
>   - Improved English in kernel doc comment
>   - Added clk_prepare_enable() return value check
>   - Added exynos_arm64_enable_bus_clk() check in
>     exynos_arm64_register_cmu()
>   - Changed the commit message to reflect code changes
> 
>  drivers/clk/samsung/clk-exynos-arm64.c | 51 ++++++++++++++++++--------
>  1 file changed, 35 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/clk/samsung/clk-exynos-arm64.c b/drivers/clk/samsung/clk-exynos-arm64.c
> index b921b9a1134a..2aa3f0a5644e 100644
> --- a/drivers/clk/samsung/clk-exynos-arm64.c
> +++ b/drivers/clk/samsung/clk-exynos-arm64.c
> @@ -56,6 +56,37 @@ static void __init exynos_arm64_init_clocks(struct device_node *np,
>  	iounmap(reg_base);
>  }
>  
> +/**
> + * exynos_arm64_enable_bus_clk - Enable parent clock of specified CMU
> + *
> + * @dev:	Device object; may be NULL if this function is not being
> + *		called from platform driver probe function
> + * @np:		CMU device tree node
> + * @cmu:	CMU data
> + *
> + * Keep CMU parent clock running (needed for CMU registers access).
> + *
> + * Return: 0 on success or a negative error code on failure.
> + */
> +static int __init exynos_arm64_enable_bus_clk(struct device *dev,
> +		struct device_node *np, const struct samsung_cmu_info *cmu)
> +{
> +	struct clk *parent_clk;
> +
> +	if (!cmu->clk_name)
> +		return 0;
> +
> +	if (dev)
> +		parent_clk = clk_get(dev, cmu->clk_name);
> +	else
> +		parent_clk = of_clk_get_by_name(np, cmu->clk_name);
> +
> +	if (IS_ERR(parent_clk))
> +		return PTR_ERR(parent_clk);
> +
> +	return clk_prepare_enable(parent_clk);
> +}
> +
>  /**
>   * exynos_arm64_register_cmu - Register specified Exynos CMU domain
>   * @dev:	Device object; may be NULL if this function is not being
> @@ -72,23 +103,11 @@ static void __init exynos_arm64_init_clocks(struct device_node *np,
>  void __init exynos_arm64_register_cmu(struct device *dev,
>  		struct device_node *np, const struct samsung_cmu_info *cmu)
>  {
> -	/* Keep CMU parent clock running (needed for CMU registers access) */
> -	if (cmu->clk_name) {
> -		struct clk *parent_clk;
> -
> -		if (dev)
> -			parent_clk = clk_get(dev, cmu->clk_name);
> -		else
> -			parent_clk = of_clk_get_by_name(np, cmu->clk_name);
> -
> -		if (IS_ERR(parent_clk)) {
> -			pr_err("%s: could not find bus clock %s; err = %ld\n",
> -			       __func__, cmu->clk_name, PTR_ERR(parent_clk));
> -		} else {
> -			clk_prepare_enable(parent_clk);
> -		}
> -	}
> +	int err;
>  
> +	err = exynos_arm64_enable_bus_clk(dev, np, cmu);
> +	if (err)
> +		panic("%s: could not enable bus clock\n", __func__);

The error handling is changed and not equivalent. I would say that we
could still try to boot even if this failed, so kernel should not panic.
Maybe the parent clock is enabled by bootloader.

Best regards,
Krzysztof