linux-kernel - Re: [PATCH v1] drm/bridge: cdns-dsi: Replace deprecated UNIVERSAL_DEV_PM

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Message-ID: <fbde0659-78f3-46e4-98cf-d832f765a18b@ideasonboard.com>
Date: Tue, 29 Apr 2025 09:32:11 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Vitor Soares <ivitro@...il.com>
Cc: Vitor Soares <vitor.soares@...adex.com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
 Jayesh Choudhary <j-choudhary@...com>, stable@...r.kernel.org,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 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>,
 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>
Subject: Re: [PATCH v1] drm/bridge: cdns-dsi: Replace deprecated
 UNIVERSAL_DEV_PM_OPS()

Hi,

On 28/04/2025 12:40, Vitor Soares wrote:
> From: Vitor Soares <vitor.soares@...adex.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
> DEFINE_RUNTIME_DEV_PM_OPS(), which avoids redundant suspend/resume calls
> by checking if the device is already runtime suspended.
> 
> Cc: <stable@...r.kernel.org> # 6.1.x
> Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
> Signed-off-by: Vitor Soares <vitor.soares@...adex.com>
> ---
>   drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 10 +++++-----
>   1 file changed, 5 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 b022dd6e6b6e..62179e55e032 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
> @@ -1258,7 +1258,7 @@ 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);
>   
> @@ -1269,7 +1269,7 @@ 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);
>   
> @@ -1279,8 +1279,8 @@ 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 DEFINE_RUNTIME_DEV_PM_OPS(cdns_dsi_pm_ops, cdns_dsi_suspend,
> +				 cdns_dsi_resume, NULL);

I'm not sure if this, or the UNIVERSAL_DEV_PM_OPS, is right here. When 
the system is suspended, the bridge drivers will get a call to the 
*_disable() hook, which then disables the device. If the bridge driver 
would additionally do something in its system suspend hook, it would 
conflict with normal disable path.

I think bridges/panels should only deal with runtime PM.

  Tomi