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

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Message-ID: <CAAfSe-uq6GszSLgtM+UBuwJ6V1Bt0_1Ard8cb6e9MMCsdpJPqw@mail.gmail.com>
Date: Wed, 22 Oct 2025 14:55:17 +0800
From: Chunyan Zhang <zhang.lyra@...il.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>, 
	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, 22 Oct 2025 at 11:09, Wenhua Lin <Wenhua.Lin@...soc.com> 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.
>
> Signed-off-by: Wenhua Lin <Wenhua.Lin@...soc.com>
> ---
>  drivers/tty/serial/sprd_serial.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> index 8c9366321f8e..092755f35683 100644
> --- a/drivers/tty/serial/sprd_serial.c
> +++ b/drivers/tty/serial/sprd_serial.c
> @@ -1133,6 +1133,9 @@ static int sprd_clk_init(struct uart_port *uport)
>
>         clk_uart = devm_clk_get(uport->dev, "uart");
>         if (IS_ERR(clk_uart)) {
> +               if (PTR_ERR(clk_uart) == -EPROBE_DEFER)
> +                       return -EPROBE_DEFER;
> +

You are making this clock mandatory, sprd_serial driver could work as
serial ports for logs output without this "uart" clock.

>                 dev_warn(uport->dev, "uart%d can't get uart clock\n",
>                          uport->line);
>                 clk_uart = NULL;
> @@ -1140,6 +1143,9 @@ static int sprd_clk_init(struct uart_port *uport)
>
>         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;
> --
> 2.34.1
>