linux-kernel - Re: [PATCH 2/2] drm/bridge: fsl-ldb: make warning message more informative

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Message-ID: <47b0e1a1-1333-402e-b316-efc4dd9eee50@nxp.com>
Date: Mon, 10 Mar 2025 15:13:49 +0800
From: Liu Ying <victor.liu@....com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: 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>,
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/bridge: fsl-ldb: make warning message more
 informative

On 03/07/2025, Luca Ceresoli wrote:
> Hello Liu,

Hello Luca,

> 
> thanks for your reviews.
> 
> On Fri, 7 Mar 2025 14:33:37 +0800
> Liu Ying <victor.liu@....com> wrote:
> 
>> On 03/07/2025, Luca Ceresoli wrote:
>>> This warning notifies a clock was set to an inaccurate value. Modify the
>>> string to also show the clock name.
>>>
>>> While doing that also rewrap the entire function call.
>>>
>>> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
>>> ---
>>>  drivers/gpu/drm/bridge/fsl-ldb.c | 6 +++---
>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c
>>> index 0fc8a14fd80062248a43b8b93272101a7ca6158a..c7c899a9644bb827845fb3fe96a9695d79a91474 100644
>>> --- a/drivers/gpu/drm/bridge/fsl-ldb.c
>>> +++ b/drivers/gpu/drm/bridge/fsl-ldb.c
>>> @@ -181,9 +181,9 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge,
>>>  
>>>  	configured_link_freq = clk_get_rate(fsl_ldb->clk);
>>>  	if (configured_link_freq != requested_link_freq)
>>> -		dev_warn(fsl_ldb->dev, "Configured LDB clock (%lu Hz) does not match requested LVDS clock: %lu Hz\n",
>>> -			 configured_link_freq,
>>> -			 requested_link_freq);
>>> +		dev_warn(fsl_ldb->dev,
>>> +			 "Configured %pC clock (%lu Hz) does not match requested LVDS clock: %lu Hz\n",
>>> +			 fsl_ldb->clk, configured_link_freq, requested_link_freq);  
>>
>> Though this slightly changes the warning message userspace sees, I guess it is
>> acceptable.
>>
>> Does it make sense to s/%pC/%pCn/ so that the clock name is printed in lower
>> case instead of upper case, since it seems that all i.MX specific clock names
>> are in lower case?
> 
> %pC and %pCn print the same string, as I just discovered at
> https://elixir.bootlin.com/linux/v6.14-rc5/source/lib/vsprintf.c#L1972

Ack.

> 
> I've pondering for a moment about whether we should document %pC and
> %pCn produce the same output or rather %pCn. I decided to try the
> latter and just sent a patch to do it [0].
> 
> FYI in my case the printed value is (with both %pC and %pCn)
> "32ec0000.blk-ctrl:bridge@5c".

This is the LDB device name. The i.MX8MP LDB clock name is "media_ldb_root_clk".

Acked-by: Liu Ying <victor.liu@....com>

> 
> [0] https://lore.kernel.org/20250307-vsprintf-pcn-v1-0-df0b2ccf610f@bootlin.com
> 
> Luca
> 

-- 
Regards,
Liu Ying