[PATCH] rtc: m41t80: use devm for the square wave clock provider

[PATCH] rtc: m41t80: use devm for the square wave clock provider

[Wentao Liang]

m41t80_sqw_register_clk() registers the square wave clock with
clk_register() and publishes it with of_clk_add_provider(), but neither is
ever torn down again: m41t80_remove() only unregisters the watchdog.

The provider therefore keeps a reference to the device node and points at
m41t80->sqw, which lives in devm-allocated driver data that is freed when
the device is unbound. Resolving the clock afterwards dereferences freed
memory.

Switch to devm_clk_hw_register() and devm_of_clk_add_hw_provider() so that
the clock and its provider are released with the device. The function no
longer returns a struct clk pointer, so make it return an int instead.

Fixes: 1373e77b4f10 ("rtc: m41t80: add clock provider support")
Cc: stable@vger.kernel.org
Assisted-by: DeepSeek-V4.1-Flash and OpenAI Codex
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
 drivers/rtc/rtc-m41t80.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 1385cb43864b..c20b8734cb66 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -563,13 +563,12 @@ static const struct clk_ops m41t80_sqw_ops = {
 	.set_rate = m41t80_sqw_set_rate,
 };
 
-static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
+static int m41t80_sqw_register_clk(struct m41t80_data *m41t80)
 {
 	struct i2c_client *client = m41t80->client;
 	struct device_node *node = client->dev.of_node;
 	struct device_node *fixed_clock;
 	struct clk_init_data init = {};
-	struct clk *clk;
 	int ret;
 
 	fixed_clock = of_get_child_by_name(node, "clock");
@@ -580,17 +579,17 @@ static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
 		 * registered automatically when being referenced.
 		 */
 		of_node_put(fixed_clock);
-		return NULL;
+		return 0;
 	}
 
 	/* First disable the clock */
 	ret = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_MON);
 	if (ret < 0)
-		return ERR_PTR(ret);
+		return ret;
 	ret = i2c_smbus_write_byte_data(client, M41T80_REG_ALARM_MON,
 					ret & ~(M41T80_ALMON_SQWE));
 	if (ret < 0)
-		return ERR_PTR(ret);
+		return ret;
 
 	init.name = "m41t80-sqw";
 	init.ops = &m41t80_sqw_ops;
@@ -604,11 +603,12 @@ static struct clk *m41t80_sqw_register_clk(struct m41t80_data *m41t80)
 	of_property_read_string(node, "clock-output-names", &init.name);
 
 	/* register the clock */
-	clk = clk_register(&client->dev, &m41t80->sqw);
-	if (!IS_ERR(clk))
-		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+	ret = devm_clk_hw_register(&client->dev, &m41t80->sqw);
+	if (ret)
+		return ret;
 
-	return clk;
+	return devm_of_clk_add_hw_provider(&client->dev, of_clk_hw_simple_get,
+					   &m41t80->sqw);
 }
 #endif
 
-- 
2.34.1

Re: [PATCH] rtc: m41t80: use devm for the square wave clock provider

[sashiko-bot]

> m41t80_sqw_register_clk() registers the square wave clock with
> clk_register() and publishes it with of_clk_add_provider(), but neither is
> ever torn down again: m41t80_remove() only unregisters the watchdog.
> 
> The provider therefore keeps a reference to the device node and points at
> m41t80->sqw, which lives in devm-allocated driver data that is freed when
> the device is unbound. Resolving the clock afterwards dereferences freed
> memory.
> 
> Switch to devm_clk_hw_register() and devm_of_clk_add_hw_provider() so that
> the clock and its provider are released with the device. The function no
> longer returns a struct clk pointer, so make it return an int instead.
> 
> Fixes: 1373e77b4f10 ("rtc: m41t80: add clock provider support")
> Cc: stable@vger.kernel.org
> Assisted-by: DeepSeek-V4.1-Flash and OpenAI Codex
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261103105808.1395292-1-vulab@iscas.ac.cn?part=1