Re: [PATCH 2/2] drm/msm/dpu: don't play tricks with debug macros

[Abhinav Kumar]

On 7/10/2024 12:40 AM, Dmitry Baryshkov wrote:
> On Tue, 9 Jul 2024 at 22:39, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
> > On 7/9/2024 6:48 AM, Dmitry Baryshkov wrote:
> > > DPU debugging macros need to be converted to a proper drm_debug_*
> > > macros, however this is a going an intrusive patch, not suitable for a
> > > fix. Wire DPU_DEBUG and DPU_DEBUG_DRIVER to always use DRM_DEBUG_DRIVER
> > > to make sure that DPU debugging messages always end up in the drm debug
> > > messages and are controlled via the usual drm.debug mask.
> >
> > These macros have been deprecated, is this waht you meant by the
> > conversion to proper drm_debug_*?
>
> Yes. Drop the driver-specific wrappers where they don't make sense.
> Use sensible format strings in the cases where it actually does (like
> VIDENC or _PLANE)

Ack but we need to not just drop the wrappers but drop the usage of 
these macros as well because it is documented that they are deprecated.

So I assume you want to get this in and do that as a follow up change?

> > /* NOTE: this is deprecated in favor of drm_dbg(NULL, ...). */
> > #define DRM_DEBUG_DRIVER(fmt, ...)                                      \
> >           __drm_dbg(DRM_UT_DRIVER, fmt, ##__VA_ARGS__)
> >
> > I think all that this macro was doing was to have appropriate DRM_UT_*
> > macros enabled before calling the corresponding DRM_DEBUG_* macros. But
> > I think what was incorrect here is for DPU_DEBUG, we could have used
> > DRM_UT_CORE instead of DRM_UT_KMS.
>
> It pretty much tries to overplay the existing drm debugging mechanism
> by either sending the messages to the DRM channel or just using
> pr_debug. With DYNAMIC_DEBUG being disabled pr_debug is just an empty
> macro, so all the messages can end up in /dev/null. We should not be
> trying to be too smart, using standard DRM_DEBUG_DRIVER should be
> enough. This way all driver-related messages are controlled by
> drm.debug including or excluding the 0x02 bit.
>
>
> > And DRM_DEBUG_DRIVER should have been used instead of DRM_ERROR.
> >
> > Was this causing the issue of the prints not getting enabled?
>
> I pretty much think so.

Alright, I am okay with the approach, just one minor suggestion, to keep 
the behavior intact, previously the code wanted DPU_DEBUG to be 
controlled by DRM_UT_KMS and DPU_DEBUG_DRIVER controlled by DRM_UT_DRIVER.

Keeping that intact, we need to use DRM_DEBUG_KMS for DPU_DEBUG?

> > > Fixes: 25fdd5933e4c ("drm/msm: Add SDM845 DPU support")
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h | 14 ++------------
> > >    1 file changed, 2 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> > > index e2adc937ea63..935ff6fd172c 100644
> > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.h
> > > @@ -31,24 +31,14 @@
> > >     * @fmt: Pointer to format string
> > >     */
> > >    #define DPU_DEBUG(fmt, ...)                                                \
> > > -     do {                                                               \
> > > -             if (drm_debug_enabled(DRM_UT_KMS))                         \
> > > -                     DRM_DEBUG(fmt, ##__VA_ARGS__); \
> > > -             else                                                       \
> > > -                     pr_debug(fmt, ##__VA_ARGS__);                      \
> > > -     } while (0)
> > > +     DRM_DEBUG_DRIVER(fmt, ##__VA_ARGS__)
> > >
> > >    /**
> > >     * DPU_DEBUG_DRIVER - macro for hardware driver logging
> > >     * @fmt: Pointer to format string
> > >     */
> > >    #define DPU_DEBUG_DRIVER(fmt, ...)                                         \
> > > -     do {                                                               \
> > > -             if (drm_debug_enabled(DRM_UT_DRIVER))                      \
> > > -                     DRM_ERROR(fmt, ##__VA_ARGS__); \
> > > -             else                                                       \
> > > -                     pr_debug(fmt, ##__VA_ARGS__);                      \
> > > -     } while (0)
> > > +     DRM_DEBUG_DRIVER(fmt, ##__VA_ARGS__)
> > >
> > >    #define DPU_ERROR(fmt, ...) pr_err("[dpu error]" fmt, ##__VA_ARGS__)
> > >    #define DPU_ERROR_RATELIMITED(fmt, ...) pr_err_ratelimited("[dpu error]" fmt, ##__VA_ARGS__)