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

Liu Ying
2025-03-10T07:12:41Z

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@nxp.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@bootlin.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@nxp.com>

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

--
Regards,
Liu Ying