Re: [PATCH 2/2] drm/rockchip: dsi: Don't log errors on deferred dphy

[Dragan Simic]

Hello Sebastian,

On 2024-11-08 15:08, Sebastian Reichel wrote:
> On Fri, Nov 08, 2024 at 02:53:58PM +0100, Dragan Simic wrote:
> > Deferred driver probing shouldn't result in errors or warnings being 
> > logged,
> > because their presence in the kernel log provides no value and may 
> > actually
> > cause false impression that some issues exist.  Thus, let's no longer 
> > produce
> > error messages when getting the dphy results in deferred probing.
> >
> > This prevents misleading error messages like the following one, which 
> > was
> > observed on a Pine64 PineTab2, from appearing in the kernel log.  To 
> > make
> > matters worse, the following error message was observed appearing 
> > multiple
> > times in the kernel log of a single PineTab2 boot:
> >
> >   dw-mipi-dsi-rockchip fe060000.dsi: [drm:dw_mipi_dsi_rockchip_probe \
> >   [rockchipdrm]] *ERROR* failed to get mipi dphy: -517
> >
> > At the same time, make the adjusted logged message a bit more 
> > consistent with
> > the other logged messages by capitalizing its first word.
> >
> > Reported-by: Diederik de Haas <didi.debian@xxxxxxxxx>
> > Signed-off-by: Dragan Simic <dsimic@xxxxxxxxxxx>
> > ---
>
> From include/drm/drm_print.h:
>
>  * DRM_DEV_ERROR() - Error output.
>  *
>  * NOTE: this is deprecated in favor of drm_err() or dev_err().
>
> The recommended way to do this nowadays looks like this:
>
> return dev_err_probe(dev, PTR_ERR(dsi->phy), "Failed to get mipi 
> dphy");
>
> That will not print anything for -EPROBE_DEFER, but capture
> the reason and make it available through
> /sys/kernel/debug/devices_deferred if the device never probes.

Thanks for your quick response!  As already discussed with Heiko,
I'll move forward with implementing a complete file-level conversion.
At first, I thought that a partial bugfix would be beneficial, [1]
but now I agree that performing a complete file-level coversion is
the way to go. [2]

I've got to admit, I love seeing that DRM_DEV_ERROR() is deprecated,
because I've never been a big fan of the format of the messages
it produces.

[1] 
https://lore.kernel.org/dri-devel/3734f6a5424e3537d717c587a058fc85@xxxxxxxxxxx/
[2] 
https://lore.kernel.org/dri-devel/047164cc6e88dcbc7701cb0e28d564db@xxxxxxxxxxx/

> >  drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c 
> > b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> > index f451e70efbdd..ffa7f2bc640d 100644
> > --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> > +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> > @@ -1387,7 +1387,8 @@ static int dw_mipi_dsi_rockchip_probe(struct 
> > platform_device *pdev)
> >  	dsi->phy = devm_phy_optional_get(dev, "dphy");
> >  	if (IS_ERR(dsi->phy)) {
> >  		ret = PTR_ERR(dsi->phy);
> > -		DRM_DEV_ERROR(dev, "failed to get mipi dphy: %d\n", ret);
> > +		if (ret != -EPROBE_DEFER)
> > +			DRM_DEV_ERROR(dev, "Failed to get mipi dphy: %d\n", ret);
> >  		return ret;
> >  	}