Re: [PATCH v4] drm/bridge: cdns-dsi: Replace deprecated UNIVERSAL_DEV_PM_OPS()

[Vitor Soares <ivitro@gmail.com>]

Hi Luca,

Thanks you for the feedback.

On Thu, 2026-04-30 at 10:10 +0200, Luca Ceresoli wrote:
> On Tue Apr 7, 2026 at 4:41 PM CEST, Vitor Soares wrote:
> > From: Vitor Soares <vitor.soares@toradex.com>
> > 
> > The deprecated UNIVERSAL_DEV_PM_OPS() macro uses the provided callbacks
> > for both runtime PM and system sleep. This causes the DSI clocks to be
> > disabled twice: once during runtime suspend and again during system
> > suspend, resulting in a WARN message from the clock framework when
> > attempting to disable already-disabled clocks.
> > 
> > [   84.384540] clk:231:5 already disabled
> > [   84.388314] WARNING: CPU: 2 PID: 531 at /drivers/clk/clk.c:1181
> > clk_core_disable+0xa4/0xac
> > ...
> > [   84.579183] Call trace:
> > [   84.581624]  clk_core_disable+0xa4/0xac
> > [   84.585457]  clk_disable+0x30/0x4c
> > [   84.588857]  cdns_dsi_suspend+0x20/0x58 [cdns_dsi]
> > [   84.593651]  pm_generic_suspend+0x2c/0x44
> > [   84.597661]  ti_sci_pd_suspend+0xbc/0x15c
> > [   84.601670]  dpm_run_callback+0x8c/0x14c
> > [   84.605588]  __device_suspend+0x1a0/0x56c
> > [   84.609594]  dpm_suspend+0x17c/0x21c
> > [   84.613165]  dpm_suspend_start+0xa0/0xa8
> > [   84.617083]  suspend_devices_and_enter+0x12c/0x634
> > [   84.621872]  pm_suspend+0x1fc/0x368
> > 
> > To address this issue, replace UNIVERSAL_DEV_PM_OPS() with
> > SET_RUNTIME_PM_OPS(), enabling suspend/resume handling through the
> 
> This is not what the patch does, the patch uses RUNTIME_PM_OPS.
> 

I missed changing it. I will send another version fixing the commit message
to RUNTIME_PM_OPS().

> > _enable()/_disable() hooks managed by the DRM framework for both
> > runtime and system-wide PM.
> > 
> > Cc: stable@vger.kernel.org # 6.1.x
> > Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
> > Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> > Signed-off-by: Vitor Soares <vitor.soares@toradex.com>
> > ---
> > v3 -> v4
> >  - Add Reviewed-by from Tomi Valkeinen
> >  - Rebase on top of drm-misc-fixes
> >  - Verified issue still present on current mainline
> > 
> > v2 -> v3
> >  - Fix warning: 'cdns_dsi_suspend' defined but not used [-Wunused-function]
> >  - Fix warning: 'cdns_dsi_resume' defined but not used [-Wunused-function]
> > 
> > v1 -> v2
> >  - Rely only on SET_RUNTIME_PM_OPS() for the PM.
> > 
> >  drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> > b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> > index 0dd85e26248c..e07a9892df4e 100644
> > --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> > +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> > @@ -1230,7 +1230,7 @@ static const struct mipi_dsi_host_ops cdns_dsi_ops = {
> >         .transfer = cdns_dsi_transfer,
> >  };
> > 
> > -static int __maybe_unused cdns_dsi_resume(struct device *dev)
> > +static int cdns_dsi_resume(struct device *dev)
> >  {
> >         struct cdns_dsi *dsi = dev_get_drvdata(dev);
> > 
> > @@ -1241,7 +1241,7 @@ static int __maybe_unused cdns_dsi_resume(struct
> > device *dev)
> >         return 0;
> >  }
> > 
> > -static int __maybe_unused cdns_dsi_suspend(struct device *dev)
> > +static int cdns_dsi_suspend(struct device *dev)
> >  {
> >         struct cdns_dsi *dsi = dev_get_drvdata(dev);
> > 
> > @@ -1251,8 +1251,9 @@ static int __maybe_unused cdns_dsi_suspend(struct
> > device *dev)
> >         return 0;
> >  }
> > 
> > -static UNIVERSAL_DEV_PM_OPS(cdns_dsi_pm_ops, cdns_dsi_suspend,
> > cdns_dsi_resume,
> > -                           NULL);
> > +static const struct dev_pm_ops cdns_dsi_pm_ops = {
> > +       RUNTIME_PM_OPS(cdns_dsi_suspend, cdns_dsi_resume, NULL)
> > +};
> 
> Not an expert here, but the docs [0] suggest using
> DEFINE_RUNTIME_DEV_PM_OPS(). Is there a good reason to not do so?
> 
> [0]
> https://elixir.bootlin.com/linux/v7.0.1/source/include/linux/pm.h#L455-L456
> 
> Luca
> 

In an earlier discussion [0], we concluded that bridges/panels should only deal
with runtime PM:

[0]
https://lore.kernel.org/all/a1cf67da-a0cb-46c5-b22b-10ecca8ab383@ideasonboard.com/

Best regards,
Vitor Soares