[PATCHv2] rtc: stmp3xxx: use devm_platform_ioremap_resource()

[PATCHv2] rtc: stmp3xxx: use devm_platform_ioremap_resource()

[Rosen Penev]

Replace the open-coded platform_get_resource() plus devm_ioremap()
sequence with a single devm_platform_ioremap_resource() call, which folds
the resource lookup and mapping into one step and returns an ERR_PTR on
failure, checked with IS_ERR() and propagated via PTR_ERR().

Move the mapping ahead of the devm_kzalloc() so that an error or deferred
probe is handled before the rtc_data allocation, avoiding needless work.

The fsl,stmp3xxx-rtc nodes in imx23.dtsi (reg = <0x8005c000 0x2000>) and
imx28.dtsi (reg = <0x80056000 0x2000>) each provide a single
non-overlapping IORESOURCE_MEM window, so the region reservation now
performed by devm_platform_ioremap_resource() introduces no conflict.

Remove irq_alarm from private struct. It's only used in _probe. Also add
check for platform_get_irq() errors.

Assisted-by: opencode:hy3-free
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: add platform_get_irq error check
 drivers/rtc/rtc-stmp3xxx.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/drivers/rtc/rtc-stmp3xxx.c b/drivers/rtc/rtc-stmp3xxx.c
index 7afcd14aeee5..e789458ba96a 100644
--- a/drivers/rtc/rtc-stmp3xxx.c
+++ b/drivers/rtc/rtc-stmp3xxx.c
@@ -56,7 +56,6 @@
 struct stmp3xxx_rtc_data {
 	struct rtc_device *rtc;
 	void __iomem *io;
-	int irq_alarm;
 };
 
 #if IS_ENABLED(CONFIG_STMP3XXX_RTC_WATCHDOG)
@@ -245,29 +244,25 @@ static void stmp3xxx_rtc_remove(struct platform_device *pdev)
 static int stmp3xxx_rtc_probe(struct platform_device *pdev)
 {
 	struct stmp3xxx_rtc_data *rtc_data;
-	struct resource *r;
+	void __iomem *io;
 	u32 rtc_stat;
 	u32 pers0_set, pers0_clr;
 	u32 crystalfreq = 0;
 	int err;
 
+	irq_alarm = platform_get_irq(pdev, 0);
+	if (irq_alarm < 0)
+		return irq_alarm;
+
+	io = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(io))
+		return PTR_ERR(io);
+
 	rtc_data = devm_kzalloc(&pdev->dev, sizeof(*rtc_data), GFP_KERNEL);
 	if (!rtc_data)
 		return -ENOMEM;
 
-	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!r) {
-		dev_err(&pdev->dev, "failed to get resource\n");
-		return -ENXIO;
-	}
-
-	rtc_data->io = devm_ioremap(&pdev->dev, r->start, resource_size(r));
-	if (!rtc_data->io) {
-		dev_err(&pdev->dev, "ioremap failed\n");
-		return -EIO;
-	}
-
-	rtc_data->irq_alarm = platform_get_irq(pdev, 0);
+	rtc_data->io = io;
 
 	rtc_stat = readl(rtc_data->io + STMP3XXX_RTC_STAT);
 	if (!(rtc_stat & STMP3XXX_RTC_STAT_RTC_PRESENT)) {
@@ -354,13 +349,10 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
 	if (IS_ERR(rtc_data->rtc))
 		return PTR_ERR(rtc_data->rtc);
 
-	err = devm_request_irq(&pdev->dev, rtc_data->irq_alarm,
+	err = devm_request_irq(&pdev->dev, irq_alarm,
 			stmp3xxx_rtc_interrupt, 0, "RTC alarm", &pdev->dev);
-	if (err) {
-		dev_err(&pdev->dev, "Cannot claim IRQ%d\n",
-			rtc_data->irq_alarm);
+	if (err)
 		return err;
-	}
 
 	rtc_data->rtc->ops = &stmp3xxx_rtc_ops;
 	rtc_data->rtc->range_max = U32_MAX;
-- 
2.55.0

Re: [PATCHv2] rtc: stmp3xxx: use devm_platform_ioremap_resource()

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

New issues:
- [Low] The local variable `irq_alarm` is used in `stmp3xxx_rtc_probe()` without being declared.

Pre-existing issues:
- [High] The dynamically registered child watchdog device is not unregistered when the RTC driver is unbound, leading to a NULL pointer dereference.
- [High] Incorrect devm cleanup order creates a race condition where a pending interrupt can trigger a Use-After-Free by re-queueing an already-canceled work object.
--

--- Patch [1]: [PATCHv2] rtc: stmp3xxx: use devm_platform_ioremap_resource() ---
commit 9966c4bcfecfb31f7bf74af8e9b176bb32e74820
Author: Rosen Penev <rosenp@gmail.com>

rtc: stmp3xxx: use devm_platform_ioremap_resource()

This patch refactors the driver to use devm_platform_ioremap_resource()
instead of open-coding the resource lookup and mapping. It moves the
mapping ahead of the data allocation to handle deferred probes earlier.
It also removes irq_alarm from the private struct and adds an error
check for platform_get_irq().

> diff --git a/drivers/rtc/rtc-stmp3xxx.c b/drivers/rtc/rtc-stmp3xxx.c
> index 7afcd14aeee56..e789458ba96a6 100644
> --- a/drivers/rtc/rtc-stmp3xxx.c
> +++ b/drivers/rtc/rtc-stmp3xxx.c
> @@ -245,29 +244,25 @@ static void stmp3xxx_rtc_remove(struct platform_device *pdev)
>  static int stmp3xxx_rtc_probe(struct platform_device *pdev)
>  {
>  	struct stmp3xxx_rtc_data *rtc_data;
> -	struct resource *r;
> +	void __iomem *io;
>  	u32 rtc_stat;
>  	u32 pers0_set, pers0_clr;
>  	u32 crystalfreq = 0;
>  	int err;
>  
> +	irq_alarm = platform_get_irq(pdev, 0);

[Severity: Low]
Does this regression introduce a build failure?

The variable irq_alarm was removed from the private struct stmp3xxx_rtc_data,
but it is used here without being declared as a local int variable first.

> +	if (irq_alarm < 0)
> +		return irq_alarm;
> +
> +	io = devm_platform_ioremap_resource(pdev, 0);

[ ... ]

> @@ -354,13 +349,10 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
>  	if (IS_ERR(rtc_data->rtc))
>  		return PTR_ERR(rtc_data->rtc);
>  
> -	err = devm_request_irq(&pdev->dev, rtc_data->irq_alarm,
> +	err = devm_request_irq(&pdev->dev, irq_alarm,
>  			stmp3xxx_rtc_interrupt, 0, "RTC alarm", &pdev->dev);

[Severity: High]
This isn't a bug introduced by this patch, but does this devm initialization
order create a use-after-free race condition during driver unbind?

The IRQ is requested via devm_request_irq() before the RTC device is
registered via devm_rtc_register_device() further down in probe.

During driver removal, devres cleans up in reverse order: the RTC device is
unregistered first (which cancels the irqwork), and the IRQ is freed second.

If a pending hardware interrupt fires in the window between these two steps,
could stmp3xxx_rtc_interrupt() unconditionally call rtc_update_irq(), which
re-queues the irqwork on an RTC device that is about to be freed?

> -	if (err) {
> -		dev_err(&pdev->dev, "Cannot claim IRQ%d\n",
> -			rtc_data->irq_alarm);
> +	if (err)
>  		return err;
> -	}
>  
>  	rtc_data->rtc->ops = &stmp3xxx_rtc_ops;
>  	rtc_data->rtc->range_max = U32_MAX;

[Severity: High]
This is a pre-existing issue, but does the dynamically registered watchdog
device leak on driver unbind?

Looking at stmp3xxx_wdt_register() called at the end of stmp3xxx_rtc_probe(),
the watchdog child device is manually added with platform_device_add(), but
stmp3xxx_rtc_remove() doesn't appear to call platform_device_unregister()
to clean this up.

If the RTC driver is unbound via sysfs, the parent device's drvdata is
cleared and devm resources are freed. Because the child watchdog device
remains active, could a subsequent access via stmp3xxx_wdt_set_timeout()
dereference the now-NULL parent drvdata and crash the system?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260728005303.574936-1-rosenp@gmail.com?part=1