Re: [PATCH v1 03/23] drm: Discard pm_runtime_put() return value

[Liviu Dudau <liviu.dudau@arm.com>]

On Mon, Dec 22, 2025 at 08:57:35PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> 
> Multiple DRM drivers use the pm_runtime_put() return value for printing
> debug or even error messages and all of those messages are at least
> somewhat misleading.
> 
> Returning an error code from pm_runtime_put() merely means that it has
> not queued up a work item to check whether or not the device can be
> suspended and there are many perfectly valid situations in which that
> can happen, like after writing "on" to the devices' runtime PM "control"
> attribute in sysfs for one example.  It also happens when the kernel
> has been configured with CONFIG_PM unset.
> 
> For this reason, modify all of those drivers to simply discard the
> pm_runtime_put() return value which is what they should be doing.
> 
> This will facilitate a planned change of the pm_runtime_put() return
> type to void in the future.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> 
> This patch is part of a series, but it doesn't depend on anything else
> in that series.  The last patch in the series depends on it.
> 
> It can be applied by itself and if you decide to do so, please let me
> know.
> 
> Otherwise, an ACK or equivalent will be appreciated, but also the lack
> of specific criticism will be eventually regarded as consent.
> 
> ---
>  drivers/gpu/drm/arm/malidp_crtc.c                   |    6 +-----

For the malidp_crtc.c:

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

Best regards,
Liviu

>  drivers/gpu/drm/bridge/imx/imx8qm-ldb.c             |    4 +---
>  drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c            |    4 +---
>  drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c |    5 +----
>  drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c        |    5 +----
>  drivers/gpu/drm/imx/dc/dc-crtc.c                    |   12 +++---------
>  drivers/gpu/drm/vc4/vc4_hdmi.c                      |    5 +----
>  drivers/gpu/drm/vc4/vc4_vec.c                       |   12 ++----------
>  8 files changed, 11 insertions(+), 42 deletions(-)
> 
> --- a/drivers/gpu/drm/arm/malidp_crtc.c
> +++ b/drivers/gpu/drm/arm/malidp_crtc.c
> @@ -77,7 +77,6 @@ static void malidp_crtc_atomic_disable(s
>  									 crtc);
>  	struct malidp_drm *malidp = crtc_to_malidp_device(crtc);
>  	struct malidp_hw_device *hwdev = malidp->dev;
> -	int err;
>  
>  	/* always disable planes on the CRTC that is being turned off */
>  	drm_atomic_helper_disable_planes_on_crtc(old_state, false);
> @@ -87,10 +86,7 @@ static void malidp_crtc_atomic_disable(s
>  
>  	clk_disable_unprepare(hwdev->pxlclk);
>  
> -	err = pm_runtime_put(crtc->dev->dev);
> -	if (err < 0) {
> -		DRM_DEBUG_DRIVER("Failed to disable runtime power management: %d\n", err);
> -	}
> +	pm_runtime_put(crtc->dev->dev);
>  }
>  
>  static const struct gamma_curve_segment {
> --- a/drivers/gpu/drm/bridge/imx/imx8qm-ldb.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qm-ldb.c
> @@ -280,9 +280,7 @@ static void imx8qm_ldb_bridge_atomic_dis
>  	clk_disable_unprepare(imx8qm_ldb->clk_bypass);
>  	clk_disable_unprepare(imx8qm_ldb->clk_pixel);
>  
> -	ret = pm_runtime_put(dev);
> -	if (ret < 0)
> -		DRM_DEV_ERROR(dev, "failed to put runtime PM: %d\n", ret);
> +	pm_runtime_put(dev);
>  }
>  
>  static const u32 imx8qm_ldb_bus_output_fmts[] = {
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> @@ -282,9 +282,7 @@ static void imx8qxp_ldb_bridge_atomic_di
>  	if (is_split && companion)
>  		companion->funcs->atomic_disable(companion, state);
>  
> -	ret = pm_runtime_put(dev);
> -	if (ret < 0)
> -		DRM_DEV_ERROR(dev, "failed to put runtime PM: %d\n", ret);
> +	pm_runtime_put(dev);
>  }
>  
>  static const u32 imx8qxp_ldb_bus_output_fmts[] = {
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pixel-combiner.c
> @@ -181,11 +181,8 @@ static void imx8qxp_pc_bridge_atomic_dis
>  {
>  	struct imx8qxp_pc_channel *ch = bridge->driver_private;
>  	struct imx8qxp_pc *pc = ch->pc;
> -	int ret;
>  
> -	ret = pm_runtime_put(pc->dev);
> -	if (ret < 0)
> -		DRM_DEV_ERROR(pc->dev, "failed to put runtime PM: %d\n", ret);
> +	pm_runtime_put(pc->dev);
>  }
>  
>  static const u32 imx8qxp_pc_bus_output_fmts[] = {
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> @@ -127,11 +127,8 @@ static void imx8qxp_pxl2dpi_bridge_atomi
>  						  struct drm_atomic_state *state)
>  {
>  	struct imx8qxp_pxl2dpi *p2d = bridge->driver_private;
> -	int ret;
>  
> -	ret = pm_runtime_put(p2d->dev);
> -	if (ret < 0)
> -		DRM_DEV_ERROR(p2d->dev, "failed to put runtime PM: %d\n", ret);
> +	pm_runtime_put(p2d->dev);
>  
>  	if (p2d->companion)
>  		p2d->companion->funcs->atomic_disable(p2d->companion, state);
> --- a/drivers/gpu/drm/imx/dc/dc-crtc.c
> +++ b/drivers/gpu/drm/imx/dc/dc-crtc.c
> @@ -300,7 +300,7 @@ dc_crtc_atomic_disable(struct drm_crtc *
>  				drm_atomic_get_new_crtc_state(state, crtc);
>  	struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev);
>  	struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
> -	int idx, ret;
> +	int idx;
>  
>  	if (!drm_dev_enter(crtc->dev, &idx))
>  		goto out;
> @@ -313,16 +313,10 @@ dc_crtc_atomic_disable(struct drm_crtc *
>  	dc_fg_disable_clock(dc_crtc->fg);
>  
>  	/* request pixel engine power-off as plane is off too */
> -	ret = pm_runtime_put(dc_drm->pe->dev);
> -	if (ret)
> -		dc_crtc_err(crtc, "failed to put DC pixel engine RPM: %d\n",
> -			    ret);
> +	pm_runtime_put(dc_drm->pe->dev);
>  
>  	/* request display engine power-off when CRTC is disabled */
> -	ret = pm_runtime_put(dc_crtc->de->dev);
> -	if (ret < 0)
> -		dc_crtc_err(crtc, "failed to put DC display engine RPM: %d\n",
> -			    ret);
> +	pm_runtime_put(dc_crtc->de->dev);
>  
>  	drm_dev_exit(idx);
>  
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -848,7 +848,6 @@ static void vc4_hdmi_encoder_post_crtc_p
>  	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
>  	struct drm_device *drm = vc4_hdmi->connector.dev;
>  	unsigned long flags;
> -	int ret;
>  	int idx;
>  
>  	mutex_lock(&vc4_hdmi->mutex);
> @@ -867,9 +866,7 @@ static void vc4_hdmi_encoder_post_crtc_p
>  	clk_disable_unprepare(vc4_hdmi->pixel_bvb_clock);
>  	clk_disable_unprepare(vc4_hdmi->pixel_clock);
>  
> -	ret = pm_runtime_put(&vc4_hdmi->pdev->dev);
> -	if (ret < 0)
> -		drm_err(drm, "Failed to release power domain: %d\n", ret);
> +	pm_runtime_put(&vc4_hdmi->pdev->dev);
>  
>  	drm_dev_exit(idx);
>  
> --- a/drivers/gpu/drm/vc4/vc4_vec.c
> +++ b/drivers/gpu/drm/vc4/vc4_vec.c
> @@ -542,7 +542,7 @@ static void vc4_vec_encoder_disable(stru
>  {
>  	struct drm_device *drm = encoder->dev;
>  	struct vc4_vec *vec = encoder_to_vc4_vec(encoder);
> -	int idx, ret;
> +	int idx;
>  
>  	if (!drm_dev_enter(drm, &idx))
>  		return;
> @@ -556,17 +556,9 @@ static void vc4_vec_encoder_disable(stru
>  
>  	clk_disable_unprepare(vec->clock);
>  
> -	ret = pm_runtime_put(&vec->pdev->dev);
> -	if (ret < 0) {
> -		drm_err(drm, "Failed to release power domain: %d\n", ret);
> -		goto err_dev_exit;
> -	}
> +	pm_runtime_put(&vec->pdev->dev);
>  
>  	drm_dev_exit(idx);
> -	return;
> -
> -err_dev_exit:
> -	drm_dev_exit(idx);
>  }
>  
>  static void vc4_vec_encoder_enable(struct drm_encoder *encoder,
> 
> 
>