Re: [RESEND][PATCH v1] drm: Discard pm_runtime_put() return value

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

On Wed, Jan 14, 2026 at 01:03:25PM +0100, Rafael J. Wysocki wrote:
> On Thu, Jan 8, 2026 at 4:38 PM Rafael J. Wysocki <rafael@kernel.org> 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>
> > Acked-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> > Acked-by: Liviu Dudau <liviu.dudau@arm.com>
> > ---
> >
> > This patch is requisite for converting pm_runtime_put() into a void
> > function.
> >
> > If you decide to pick it up, 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.
> >
> > Originally posted here:
> >
> > https://lore.kernel.org/linux-pm/3045480.e9J7NaK4W3@rafael.j.wysocki/
> 
> This is the last patch from the "discard pm_runtime_put() return
> values" lot that has not been applied yet, AFAICS, so this is the last
> call for objections or concerns related to it.

I think you can go ahead and apply it, I don't see how the imx8 driver will
be affected by the lack of debug messages.

Best regards,
Liviu

> 
> > ---
> >  drivers/gpu/drm/arm/malidp_crtc.c                   |    6 +-----
> >  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,
> >
> >
> >
> >