linux-kernel - Re: [PATCH v4 1/2] hwrng: imx-rngc: Use optional clock

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Message-ID: <aSdjT9BLzGF3_5PB@akranes.kaiser.cx>
Date: Wed, 26 Nov 2025 21:30:07 +0100
From: Martin Kaiser <martin@...ser.cx>
To: Jean-Michel Hautbois via B4 Relay <devnull+jeanmichel.hautbois.yoseli.org@...nel.org>
Cc: Greg Ungerer <gerg@...ux-m68k.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Olivia Mackall <olivia@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-m68k@...ts.linux-m68k.org,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>,
	Frank Li <Frank.Li@....com>
Subject: Re: [PATCH v4 1/2] hwrng: imx-rngc: Use optional clock

Thus wrote Jean-Michel Hautbois via B4 Relay (devnull+jeanmichel.hautbois.yoseli.org@...nel.org):

> From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>

> Change devm_clk_get() to devm_clk_get_optional() to support platforms
> where the RNG clock is always enabled and not exposed via the clock
> framework (such as ColdFire MCF54418).

> Reviewed-by: Frank Li <Frank.Li@....com>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
> ---
>  drivers/char/hw_random/imx-rngc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c
> index 241664a9b5d9..d6a847e48339 100644
> --- a/drivers/char/hw_random/imx-rngc.c
> +++ b/drivers/char/hw_random/imx-rngc.c
> @@ -259,7 +259,7 @@ static int __init imx_rngc_probe(struct platform_device *pdev)
>  	if (IS_ERR(rngc->base))
>  		return PTR_ERR(rngc->base);

> -	rngc->clk = devm_clk_get(&pdev->dev, NULL);
> +	rngc->clk = devm_clk_get_optional(&pdev->dev, NULL);
>  	if (IS_ERR(rngc->clk))
>  		return dev_err_probe(&pdev->dev, PTR_ERR(rngc->clk), "Cannot get rng_clk\n");

The clock is not optional on a standard imx25 system. If it's missing in the
device tree, the rngb will not work and we should not load the driver.

Should we call devm_clk_get or devm_clk_get_optional, depending on the
detected device?

Best regards,
Martin