rtc: mv: fix potential race condition

Since the driver allocates the IRQ using devm_request_irq(), this means the
IRQ is going to be automatically unregistered by devres after
mv_rtc_remove() returns.

However, mv_rtc_remove() explicitly disables the hardware clock before
devres teardown happens so the interrupt handler may run while the clock is
disabled leading to a possible bus hang when accessing registers.

Link: https://patch.msgid.link/20260625130202.1621692-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-mv.c b/drivers/rtc/rtc-mv.c
index f88976f..c0f1bcd 100644 (file)
--- a/drivers/rtc/rtc-mv.c
+++ b/drivers/rtc/rtc-mv.c
@@ -219,17 +219,15 @@ static int __init mv_rtc_probe(struct platform_device *pdev)
        if (IS_ERR(pdata->ioaddr))
                return PTR_ERR(pdata->ioaddr);
 
-       pdata->clk = devm_clk_get(&pdev->dev, NULL);
-       /* Not all SoCs require a clock.*/
-       if (!IS_ERR(pdata->clk))
-               clk_prepare_enable(pdata->clk);
+       pdata->clk = devm_clk_get_optional_prepared(&pdev->dev, NULL);
+       if (IS_ERR(pdata->clk))
+               return PTR_ERR(pdata->clk);
 
        /* make sure the 24 hour mode is enabled */
        rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
        if (rtc_time & RTC_HOURS_12H_MODE) {
                dev_err(&pdev->dev, "12 Hour mode is enabled but not supported.\n");
-               ret = -EINVAL;
-               goto out;
+               return  -EINVAL;
        }
 
        /* make sure it is actually functional */
@@ -238,8 +236,7 @@ static int __init mv_rtc_probe(struct platform_device *pdev)
                rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
                if (rtc_time == 0x01000000) {
                        dev_err(&pdev->dev, "internal RTC not ticking\n");
-                       ret = -ENODEV;
-                       goto out;
+                       return -ENODEV;
                }
        }
 
@@ -249,8 +246,7 @@ static int __init mv_rtc_probe(struct platform_device *pdev)
 
        pdata->rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(pdata->rtc)) {
-               ret = PTR_ERR(pdata->rtc);
-               goto out;
+               return PTR_ERR(pdata->rtc);
        }
 
        if (pdata->irq >= 0) {
@@ -275,9 +271,6 @@ static int __init mv_rtc_probe(struct platform_device *pdev)
        ret = devm_rtc_register_device(pdata->rtc);
        if (!ret)
                return 0;
-out:
-       if (!IS_ERR(pdata->clk))
-               clk_disable_unprepare(pdata->clk);
 
        return ret;
 }
@@ -288,9 +281,6 @@ static void __exit mv_rtc_remove(struct platform_device *pdev)
 
        if (pdata->irq >= 0)
                device_init_wakeup(&pdev->dev, false);
-
-       if (!IS_ERR(pdata->clk))
-               clk_disable_unprepare(pdata->clk);
 }
 
 #ifdef CONFIG_OF