[PATCH 1/2] drm/arm/malidp: fix ignored clk_prepare_enable() in runtime PM resume

[PATCH 1/2] drm/arm/malidp: fix ignored clk_prepare_enable() in runtime PM resume

[Gustavo Kenji Mendonça Kaneko]

malidp_runtime_pm_resume() calls clk_prepare_enable() three times
without checking the return value. If any clock fails to enable, the
driver silently proceeds with unclocked hardware, leading to undefined
behavior.

Use clk_bulk_prepare_enable() which atomically enables all clocks and
automatically rolls back successfully enabled clocks on failure. This
is consistent with how the suspend path already uses
clk_bulk_disable_unprepare() in malidp_runtime_pm_suspend().

This issue was found by code review without access to Mali DP hardware.

Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@pm.me>
---
 drivers/gpu/drm/arm/malidp_drv.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
index b765f6c9eea4..1e4336c3a2fa 100644
--- a/drivers/gpu/drm/arm/malidp_drv.c
+++ b/drivers/gpu/drm/arm/malidp_drv.c
@@ -689,10 +689,17 @@ static int malidp_runtime_pm_resume(struct device *dev)
 	struct drm_device *drm = dev_get_drvdata(dev);
 	struct malidp_drm *malidp = drm_to_malidp(drm);
 	struct malidp_hw_device *hwdev = malidp->dev;
+	struct clk_bulk_data clks[] = {
+		{ .clk = hwdev->pclk },
+		{ .clk = hwdev->aclk },
+		{ .clk = hwdev->mclk },
+	};
+	int err;
+
+	err = clk_bulk_prepare_enable(ARRAY_SIZE(clks), clks);
+	if (err)
+		return err;
 
-	clk_prepare_enable(hwdev->pclk);
-	clk_prepare_enable(hwdev->aclk);
-	clk_prepare_enable(hwdev->mclk);
 	hwdev->pm_suspended = false;
 	malidp_de_irq_hw_init(hwdev);
 	malidp_se_irq_hw_init(hwdev);
-- 
2.54.0

[PATCH 2/2] drm/arm/komeda: fix ignored clk_prepare_enable() return value in resume

[Gustavo Kenji Mendonça Kaneko]

komeda_dev_resume() calls clk_prepare_enable() without checking the
return value. If the clock fails to enable, the function returns 0
(success) while IRQs are enabled and IOMMU is connected on potentially
unclocked hardware, causing undefined behavior on resume.

Propagate the error from clk_prepare_enable() and return early on
failure to prevent hardware access without a valid clock.

This issue was found by code review without access to Komeda hardware.

Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@pm.me>
---
 drivers/gpu/drm/arm/display/komeda/komeda_dev.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
index 5ba62e637a61..9aad1d1d28ec 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
@@ -313,7 +313,11 @@ void komeda_dev_destroy(struct komeda_dev *mdev)
 
 int komeda_dev_resume(struct komeda_dev *mdev)
 {
-	clk_prepare_enable(mdev->aclk);
+	int err;
+
+	err = clk_prepare_enable(mdev->aclk);
+	if (err)
+		return err;
 
 	mdev->funcs->enable_irq(mdev);
 
-- 
2.54.0

Re: [PATCH 1/2] drm/arm/malidp: fix ignored clk_prepare_enable() in runtime PM resume

[Liviu Dudau]

On Sun, May 31, 2026 at 05:29:57AM +0000, Gustavo Kenji Mendonça Kaneko wrote:
> malidp_runtime_pm_resume() calls clk_prepare_enable() three times
> without checking the return value. If any clock fails to enable, the
> driver silently proceeds with unclocked hardware, leading to undefined
> behavior.
> 
> Use clk_bulk_prepare_enable() which atomically enables all clocks and
> automatically rolls back successfully enabled clocks on failure. This
> is consistent with how the suspend path already uses
> clk_bulk_disable_unprepare() in malidp_runtime_pm_suspend().
> 
> This issue was found by code review without access to Mali DP hardware.
> 
> Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@pm.me>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/arm/malidp_drv.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
> index b765f6c9eea4..1e4336c3a2fa 100644
> --- a/drivers/gpu/drm/arm/malidp_drv.c
> +++ b/drivers/gpu/drm/arm/malidp_drv.c
> @@ -689,10 +689,17 @@ static int malidp_runtime_pm_resume(struct device *dev)
>  	struct drm_device *drm = dev_get_drvdata(dev);
>  	struct malidp_drm *malidp = drm_to_malidp(drm);
>  	struct malidp_hw_device *hwdev = malidp->dev;
> +	struct clk_bulk_data clks[] = {
> +		{ .clk = hwdev->pclk },
> +		{ .clk = hwdev->aclk },
> +		{ .clk = hwdev->mclk },
> +	};
> +	int err;
> +
> +	err = clk_bulk_prepare_enable(ARRAY_SIZE(clks), clks);
> +	if (err)
> +		return err;
>  
> -	clk_prepare_enable(hwdev->pclk);
> -	clk_prepare_enable(hwdev->aclk);
> -	clk_prepare_enable(hwdev->mclk);
>  	hwdev->pm_suspended = false;
>  	malidp_de_irq_hw_init(hwdev);
>  	malidp_se_irq_hw_init(hwdev);
> -- 
> 2.54.0
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

Re: [PATCH 2/2] drm/arm/komeda: fix ignored clk_prepare_enable() return value in resume

[Liviu Dudau]

On Sun, May 31, 2026 at 05:30:02AM +0000, Gustavo Kenji Mendonça Kaneko wrote:
> komeda_dev_resume() calls clk_prepare_enable() without checking the
> return value. If the clock fails to enable, the function returns 0
> (success) while IRQs are enabled and IOMMU is connected on potentially
> unclocked hardware, causing undefined behavior on resume.
> 
> Propagate the error from clk_prepare_enable() and return early on
> failure to prevent hardware access without a valid clock.
> 
> This issue was found by code review without access to Komeda hardware.

Hello,

There is nothing wrong with the content of this patch, but I would like
if anyone wants to fix these kind of problems to at least be thorough.

komeda_dev_suspend() is also ignoring the errors coming from
clk_disable_unprepare() and both fuctions before this patch always return 0,
so in komeda_drv.c we can sometimes ignore the return value. If we add
an extended version of this patch then we should also do proper error
handling in komeda_drv.c

Best regards,
Liviu


> 
> Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@pm.me>
> ---
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> index 5ba62e637a61..9aad1d1d28ec 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.c
> @@ -313,7 +313,11 @@ void komeda_dev_destroy(struct komeda_dev *mdev)
>  
>  int komeda_dev_resume(struct komeda_dev *mdev)
>  {
> -	clk_prepare_enable(mdev->aclk);
> +	int err;
> +
> +	err = clk_prepare_enable(mdev->aclk);
> +	if (err)
> +		return err;
>  
>  	mdev->funcs->enable_irq(mdev);
>  
> -- 
> 2.54.0
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

Re: [PATCH 1/2] drm/arm/malidp: fix ignored clk_prepare_enable() in runtime PM resume

[Liviu Dudau]

On Sun, May 31, 2026 at 05:29:57AM +0000, Gustavo Kenji Mendonça Kaneko wrote:
> malidp_runtime_pm_resume() calls clk_prepare_enable() three times
> without checking the return value. If any clock fails to enable, the
> driver silently proceeds with unclocked hardware, leading to undefined
> behavior.
> 
> Use clk_bulk_prepare_enable() which atomically enables all clocks and
> automatically rolls back successfully enabled clocks on failure. This
> is consistent with how the suspend path already uses
> clk_bulk_disable_unprepare() in malidp_runtime_pm_suspend().

I can't see where you can find other calls to clk_buld_xxxx() in the malidp
code. What sort of code review have you done here?

Best regards,
Liviu

> 
> This issue was found by code review without access to Mali DP hardware.
> 
> Signed-off-by: Gustavo Kenji Mendonça Kaneko <kaneko.dev@pm.me>
> ---
>  drivers/gpu/drm/arm/malidp_drv.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/malidp_drv.c b/drivers/gpu/drm/arm/malidp_drv.c
> index b765f6c9eea4..1e4336c3a2fa 100644
> --- a/drivers/gpu/drm/arm/malidp_drv.c
> +++ b/drivers/gpu/drm/arm/malidp_drv.c
> @@ -689,10 +689,17 @@ static int malidp_runtime_pm_resume(struct device *dev)
>  	struct drm_device *drm = dev_get_drvdata(dev);
>  	struct malidp_drm *malidp = drm_to_malidp(drm);
>  	struct malidp_hw_device *hwdev = malidp->dev;
> +	struct clk_bulk_data clks[] = {
> +		{ .clk = hwdev->pclk },
> +		{ .clk = hwdev->aclk },
> +		{ .clk = hwdev->mclk },
> +	};
> +	int err;
> +
> +	err = clk_bulk_prepare_enable(ARRAY_SIZE(clks), clks);
> +	if (err)
> +		return err;
>  
> -	clk_prepare_enable(hwdev->pclk);
> -	clk_prepare_enable(hwdev->aclk);
> -	clk_prepare_enable(hwdev->mclk);
>  	hwdev->pm_suspended = false;
>  	malidp_de_irq_hw_init(hwdev);
>  	malidp_se_irq_hw_init(hwdev);
> -- 
> 2.54.0
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯