2022-04-13 00:01:18

by Miaoqian Lin

[permalink] [raw]
Subject: [PATCH] drm/vc4: Fix pm_runtime_get_sync() error checking

If the device is already in a runtime PM enabled state
pm_runtime_get_sync() will return 1, so a test for negative
value should be used to check for errors.

Fixes: 4078f5757144 ("drm/vc4: Add DSI driver")
Signed-off-by: Miaoqian Lin <[email protected]>
---
drivers/gpu/drm/vc4/vc4_dsi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 752f921735c6..26aa7d1fa421 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -847,7 +847,7 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
int ret;

ret = pm_runtime_get_sync(dev);
- if (ret) {
+ if (ret < 0) {
DRM_ERROR("Failed to runtime PM enable on DSI%d\n", dsi->variant->port);
return;
}
--
2.17.1


2022-04-22 01:51:14

by Maxime Ripard

[permalink] [raw]
Subject: Re: [PATCH] drm/vc4: Fix pm_runtime_get_sync() error checking

Hi,

On Tue, Apr 12, 2022 at 07:04:57AM +0000, Miaoqian Lin wrote:
> If the device is already in a runtime PM enabled state
> pm_runtime_get_sync() will return 1, so a test for negative
> value should be used to check for errors.
>
> Fixes: 4078f5757144 ("drm/vc4: Add DSI driver")
> Signed-off-by: Miaoqian Lin <[email protected]>
> ---
> drivers/gpu/drm/vc4/vc4_dsi.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> index 752f921735c6..26aa7d1fa421 100644
> --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> @@ -847,7 +847,7 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
> int ret;
>
> ret = pm_runtime_get_sync(dev);
> - if (ret) {
> + if (ret < 0) {
> DRM_ERROR("Failed to runtime PM enable on DSI%d\n", dsi->variant->port);
> return;
> }

We also don't put back our reference after an error. I think a better
fix would be to switch to pm_runtime_resume_and_get.

Maxime

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2022-04-22 09:03:43

by Miaoqian Lin

[permalink] [raw]
Subject: [PATCH v2] drm/vc4: Fix pm_runtime_get_sync() usage

If the device is already in a runtime PM enabled state
pm_runtime_get_sync() will return 1, so a test for negative
value should be used to check for errors.

Also, we need to call pm_runtime_put_noidle() when pm_runtime_get_sync()
fails, so use pm_runtime_resume_and_get() instead. this function
will handle this.

Fixes: 4078f5757144 ("drm/vc4: Add DSI driver")
Signed-off-by: Miaoqian Lin <[email protected]>
---
change in v2:
- switch to pm_runtime_resume_and_get() to fix refcount leak.
---
drivers/gpu/drm/vc4/vc4_dsi.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 752f921735c6..9d7ffaf6bc70 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -846,8 +846,8 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
unsigned long phy_clock;
int ret;

- ret = pm_runtime_get_sync(dev);
- if (ret) {
+ ret = pm_runtime_resume_and_get(dev);
+ if (ret < 0) {
DRM_ERROR("Failed to runtime PM enable on DSI%d\n", dsi->variant->port);
return;
}
--
2.17.1