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

[Luca Ceresoli]

On Tue Apr 7, 2026 at 4:41 PM CEST, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@xxxxxxxxxxx>
>
> 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.

> _enable()/_disable() hooks managed by the DRM framework for both
> runtime and system-wide PM.
>
> Cc: stable@xxxxxxxxxxxxxxx # 6.1.x
> Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
> Signed-off-by: Vitor Soares <vitor.soares@xxxxxxxxxxx>
> ---
> 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

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com