linux-kernel - [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

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Message-ID: <20251022030840.956589-1-Wenhua.Lin@unisoc.com>
Date: Wed, 22 Oct 2025 11:08:40 +0800
From: Wenhua Lin <Wenhua.Lin@...soc.com>
To: 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>
CC: 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>,
        Wenhua
 Lin <Wenhua.Lin@...soc.com>,
        Xiongpeng Wu <xiongpeng.wu@...soc.com>,
        Zhaochen
 Su <Zhaochen.Su@...soc.com>,
        Zhirong Qiu <Zhirong.Qiu@...soc.com>
Subject: [PATCH] serial: sprd: Return -EPROBE_DEFER when uart clock is not ready

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;
+
 		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