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Message-ID: <aWjbPpkDd_SORcfC@e142607>
Date: Thu, 15 Jan 2026 12:19:10 +0000
From: Liviu Dudau <liviu.dudau@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Linux PM <linux-pm@...r.kernel.org>, imx@...ts.linux.dev,
LKML <linux-kernel@...r.kernel.org>,
Ulf Hansson <ulf.hansson@...aro.org>,
Brian Norris <briannorris@...omium.org>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Neil Armstrong <neil.armstrong@...aro.org>,
Robert Foss <rfoss@...nel.org>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
Jonas Karlman <jonas@...boo.se>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
Dave Stevenson <dave.stevenson@...pberrypi.com>,
Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>,
Maíra Canal <mcanal@...lia.com>,
dri-devel@...ts.freedesktop.org
Subject: Re: [RESEND][PATCH v1] drm: Discard pm_runtime_put() return value
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@...nel.org> wrote:
> >
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.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@...el.com>
> > Acked-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> > Acked-by: Liviu Dudau <liviu.dudau@....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,
> >
> >
> >
> >
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