New subject: [bug report] coresight: etm4x: Change etm4_platform_driver driver for MMIO devices

3 Aug 2023

Hello Dan,
On 7/29/23 12:50, Dan Carpenter wrote:
...
Hello Anshuman Khandual,
The patch 73d779a03a76: "coresight: etm4x: Change
etm4_platform_driver driver for MMIO devices" from Jul 10, 2023
(linux-next), leads to the following Smatch static checker warning:
drivers/hwtracing/coresight/coresight-etm4x-core.c:2272 etm4_remove_platform_dev()
   error: we previously assumed 'drvdata' could be null (see line 2268)
drivers/hwtracing/coresight/coresight-etm4x-core.c
    2264 static int __exit etm4_remove_platform_dev(struct platform_device *pdev)
    2265 {
    2266         struct etmv4_drvdata *drvdata = dev_get_drvdata(&pdev->dev);
    2267 
    2268         if (drvdata)
This check can probably be removed, right?
etm4_remove_dev(drvdata) cannot be called if drvdata is NULL. But there
might be an implicit assumption that 'drvdata' could never be NULL in
this path.
...
2269                 etm4_remove_dev(drvdata);
2270         pm_runtime_disable(&pdev->dev);
2271 

--> 2272         if (drvdata->pclk)
Not checked here
We could either have the following change which ensures that 'drvdata'
is checked again before the clock is handled.

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 703b6fcbb6a5..9d186af81ea0 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -2267,11 +2267,13 @@ static int __exit etm4_remove_platform_dev(struct platform_device *pdev)
if (drvdata)
                etm4_remove_dev(drvdata);
-       pm_runtime_disable(&pdev->dev);
-       if (drvdata->pclk)
-               clk_put(drvdata->pclk);
+       pm_runtime_disable(&pdev->dev);
+       if (drvdata) {
+               if (drvdata->pclk && !IS_ERR(drvdata->pclk))
+                       clk_put(drvdata->pclk);
+       }
        return 0;
 }
OR remove the first drvdata check as suggested.
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 703b6fcbb6a5..6e1ffddbd4be 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -2265,11 +2265,9 @@ static int __exit etm4_remove_platform_dev(struct platform_device *pdev)
 {
        struct etmv4_drvdata *drvdata = dev_get_drvdata(&pdev->dev);
-       if (drvdata)
-               etm4_remove_dev(drvdata);
+       etm4_remove_dev(drvdata);
        pm_runtime_disable(&pdev->dev);
-
-       if (drvdata->pclk)
+       if (drvdata->pclk && !IS_ERR(drvdata->pclk)
                clk_put(drvdata->pclk);
return 0;
...
2273                 clk_put(drvdata->pclk);
2274 
2275         return 0;
2276 }

Also adding Suzuki and James for their input.
- Anshuman

    

Re: [bug report] coresight: etm4x: Change etm4_platform_driver driver for MMIO devices