linux-kernel - Re: [PATCH] serial: sprd: Return -EPROBE

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Message-ID: <aSb5Q0Giq8p43n_o@black.igk.intel.com>
Date: Wed, 26 Nov 2025 13:57:39 +0100
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Wenhua Lin <Wenhua.Lin@...soc.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Orson Zhai <orsonzhai@...il.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	Chunyan Zhang <zhang.lyra@...il.com>,
	Cixi Geng <cixi.geng@...ux.dev>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, wenhua lin <wenhua.lin1994@...il.com>,
	Xiongpeng Wu <xiongpeng.wu@...soc.com>,
	Zhaochen Su <Zhaochen.Su@...soc.com>,
	Zhirong Qiu <Zhirong.Qiu@...soc.com>
Subject: Re: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is
 not ready

On Wed, Oct 22, 2025 at 11:08:40AM +0800, Wenhua Lin wrote:
> In sprd_clk_init(), when devm_clk_get() returns -EPROBE_DEFER
> for either uart or source clock, we should propagate the
> error instead of just warning and continuing with NULL clocks.
> 
> Currently the driver only emits a warning when clock acquisition
> fails and proceeds with NULL clock pointers. This can lead to
> issues later when the clocks are actually needed. More importantly,
> when the clock provider is not ready yet and returns -EPROBE_DEFER,
> we should return this error to allow deferred probing.
> 
> This change adds explicit checks for -EPROBE_DEFER after both:
> 1. devm_clk_get(uport->dev, uart)
> 2. devm_clk_get(uport->dev, source)
> 
> When -EPROBE_DEFER is encountered, the function now returns
> -EPROBE_DEFER to let the driver framework retry probing
> later when the clock dependencies are resolved.

...

>  	clk_uart = devm_clk_get(uport->dev, "uart");
>  	if (IS_ERR(clk_uart)) {
> +		if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +
>  		dev_warn(uport->dev, "uart%d can't get uart clock\n",
>  			 uport->line);
>  		clk_uart = NULL;

AFAICS this still ignores other issues, what should be done here is to
replace devm_clk_get() by devm_clk_get_optional() and drop this NULL
assignment.

...

>  	clk_parent = devm_clk_get(uport->dev, "source");
>  	if (IS_ERR(clk_parent)) {
> +		if (PTR_ERR(clk_parent) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +
>  		dev_warn(uport->dev, "uart%d can't get source clock\n",
>  			 uport->line);
>  		clk_parent = NULL;

Ditto.

-- 
With Best Regards,
Andy Shevchenko