[PATCH] drm/loongson: clean up KMS polling on probe failure

[PATCH] drm/loongson: clean up KMS polling on probe failure

[Myeonghun Pak]

lsdc_pci_probe() initializes KMS polling before setting up vblank support,
requesting the IRQ and registering the DRM device. If any of those later
steps fails, probe returns without finalizing polling. The remove path has
the same lifetime gap when tearing down a successfully registered device.

Route those probe failures through a poll cleanup label. Also finalize
polling from remove before unregistering the DRM device.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: f39db26c5428 ("drm: Add kms driver for loongson display controller")
Cc: stable@vger.kernel.org
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
 drivers/gpu/drm/loongson/lsdc_drv.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/loongson/lsdc_drv.c b/drivers/gpu/drm/loongson/lsdc_drv.c
index abf5bf68ee..3db1f8690a 100644
--- a/drivers/gpu/drm/loongson/lsdc_drv.c
+++ b/drivers/gpu/drm/loongson/lsdc_drv.c
@@ -297,7 +297,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (loongson_vblank) {
 		ret = drm_vblank_init(ddev, descp->num_of_crtc);
 		if (ret)
-			return ret;
+			goto err_poll_fini;
 
 		ret = devm_request_irq(&pdev->dev, pdev->irq,
 				       descp->funcs->irq_handler,
@@ -305,7 +305,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 				       dev_name(&pdev->dev), ddev);
 		if (ret) {
 			drm_err(ddev, "Failed to register interrupt: %d\n", ret);
-			return ret;
+			goto err_poll_fini;
 		}
 
 		drm_info(ddev, "registered irq: %u\n", pdev->irq);
@@ -313,17 +313,22 @@ static int lsdc_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 
 	ret = drm_dev_register(ddev, 0);
 	if (ret)
-		return ret;
+		goto err_poll_fini;
 
 	drm_client_setup(ddev, NULL);
 
 	return 0;
+
+err_poll_fini:
+	drm_kms_helper_poll_fini(ddev);
+	return ret;
 }
 
 static void lsdc_pci_remove(struct pci_dev *pdev)
 {
 	struct drm_device *ddev = pci_get_drvdata(pdev);
 
+	drm_kms_helper_poll_fini(ddev);
 	drm_dev_unregister(ddev);
 	drm_atomic_helper_shutdown(ddev);
 }
-- 
2.47.1

Re: [PATCH] drm/loongson: clean up KMS polling on probe failure

[Icenowy Zheng]

在 2026-05-12二的 02:01 +0900，Myeonghun Pak写道：
> lsdc_pci_probe() initializes KMS polling before setting up vblank
> support,
> requesting the IRQ and registering the DRM device. If any of those
> later
> steps fails, probe returns without finalizing polling. The remove
> path has
> the same lifetime gap when tearing down a successfully registered
> device.
> 
> Route those probe failures through a poll cleanup label. Also
> finalize
> polling from remove before unregistering the DRM device.

Interesting, but it looks like a `drmm_kms_helper_poll_init` function
exists (while rarely used).

Maybe it's better to switch to this? Or maybe there's some reason not
to use this?

Thanks,
Icenowy

> 
> This issue was identified during our ongoing static-analysis research
> while
> reviewing kernel code.
> 
> Fixes: f39db26c5428 ("drm: Add kms driver for loongson display
> controller")
> Cc: stable@vger.kernel.org
> Co-developed-by: Ijae Kim <ae878000@gmail.com>
> Signed-off-by: Ijae Kim <ae878000@gmail.com>
> Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
> ---
>  drivers/gpu/drm/loongson/lsdc_drv.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/loongson/lsdc_drv.c
> b/drivers/gpu/drm/loongson/lsdc_drv.c
> index abf5bf68ee..3db1f8690a 100644
> --- a/drivers/gpu/drm/loongson/lsdc_drv.c
> +++ b/drivers/gpu/drm/loongson/lsdc_drv.c
> @@ -297,7 +297,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  	if (loongson_vblank) {
>  		ret = drm_vblank_init(ddev, descp->num_of_crtc);
>  		if (ret)
> -			return ret;
> +			goto err_poll_fini;
>  
>  		ret = devm_request_irq(&pdev->dev, pdev->irq,
>  				       descp->funcs->irq_handler,
> @@ -305,7 +305,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  				       dev_name(&pdev->dev), ddev);
>  		if (ret) {
>  			drm_err(ddev, "Failed to register interrupt:
> %d\n", ret);
> -			return ret;
> +			goto err_poll_fini;
>  		}
>  
>  		drm_info(ddev, "registered irq: %u\n", pdev->irq);
> @@ -313,17 +313,22 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
> const struct pci_device_id *ent)
>  
>  	ret = drm_dev_register(ddev, 0);
>  	if (ret)
> -		return ret;
> +		goto err_poll_fini;
>  
>  	drm_client_setup(ddev, NULL);
>  
>  	return 0;
> +
> +err_poll_fini:
> +	drm_kms_helper_poll_fini(ddev);
> +	return ret;
>  }
>  
>  static void lsdc_pci_remove(struct pci_dev *pdev)
>  {
>  	struct drm_device *ddev = pci_get_drvdata(pdev);
>  
> +	drm_kms_helper_poll_fini(ddev);
>  	drm_dev_unregister(ddev);
>  	drm_atomic_helper_shutdown(ddev);
>  }

Re: [PATCH] drm/loongson: clean up KMS polling on probe failure

[Thomas Zimmermann]

Hi

Am 11.05.26 um 19:22 schrieb Icenowy Zheng:
> 在 2026-05-12二的 02:01 +0900，Myeonghun Pak写道：
>> lsdc_pci_probe() initializes KMS polling before setting up vblank
>> support,
>> requesting the IRQ and registering the DRM device. If any of those
>> later
>> steps fails, probe returns without finalizing polling. The remove
>> path has
>> the same lifetime gap when tearing down a successfully registered
>> device.
>>
>> Route those probe failures through a poll cleanup label. Also
>> finalize
>> polling from remove before unregistering the DRM device.
> Interesting, but it looks like a `drmm_kms_helper_poll_init` function
> exists (while rarely used).
>
> Maybe it's better to switch to this? Or maybe there's some reason not
> to use this?

Agreed. DRM drivers are advised to use managed cleanup for their data 
structures. So rather switch to drmm_kms_helper_poll_init(). That also 
resolves the problem that loongson never calls poll_fini on regular 
removals.

Best regards
Thomas

>
> Thanks,
> Icenowy
>
>> This issue was identified during our ongoing static-analysis research
>> while
>> reviewing kernel code.
>>
>> Fixes: f39db26c5428 ("drm: Add kms driver for loongson display
>> controller")
>> Cc: stable@vger.kernel.org
>> Co-developed-by: Ijae Kim <ae878000@gmail.com>
>> Signed-off-by: Ijae Kim <ae878000@gmail.com>
>> Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
>> ---
>>   drivers/gpu/drm/loongson/lsdc_drv.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/loongson/lsdc_drv.c
>> b/drivers/gpu/drm/loongson/lsdc_drv.c
>> index abf5bf68ee..3db1f8690a 100644
>> --- a/drivers/gpu/drm/loongson/lsdc_drv.c
>> +++ b/drivers/gpu/drm/loongson/lsdc_drv.c
>> @@ -297,7 +297,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
>> const struct pci_device_id *ent)
>>   	if (loongson_vblank) {
>>   		ret = drm_vblank_init(ddev, descp->num_of_crtc);
>>   		if (ret)
>> -			return ret;
>> +			goto err_poll_fini;
>>   
>>   		ret = devm_request_irq(&pdev->dev, pdev->irq,
>>   				       descp->funcs->irq_handler,
>> @@ -305,7 +305,7 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
>> const struct pci_device_id *ent)
>>   				       dev_name(&pdev->dev), ddev);
>>   		if (ret) {
>>   			drm_err(ddev, "Failed to register interrupt:
>> %d\n", ret);
>> -			return ret;
>> +			goto err_poll_fini;
>>   		}
>>   
>>   		drm_info(ddev, "registered irq: %u\n", pdev->irq);
>> @@ -313,17 +313,22 @@ static int lsdc_pci_probe(struct pci_dev *pdev,
>> const struct pci_device_id *ent)
>>   
>>   	ret = drm_dev_register(ddev, 0);
>>   	if (ret)
>> -		return ret;
>> +		goto err_poll_fini;
>>   
>>   	drm_client_setup(ddev, NULL);
>>   
>>   	return 0;
>> +
>> +err_poll_fini:
>> +	drm_kms_helper_poll_fini(ddev);
>> +	return ret;
>>   }
>>   
>>   static void lsdc_pci_remove(struct pci_dev *pdev)
>>   {
>>   	struct drm_device *ddev = pci_get_drvdata(pdev);
>>   
>> +	drm_kms_helper_poll_fini(ddev);
>>   	drm_dev_unregister(ddev);
>>   	drm_atomic_helper_shutdown(ddev);
>>   }

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)