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

Luca Ceresoli
2025-03-07T11:22:23Z

Hello Liu,

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

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".

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

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering