Re: [PATCH v2 5/5] drm/i915/display: Cover all possible pipes in TP_printk()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Sep 23, 2024 at 05:06:00PM -0300, Gustavo Sousa wrote:
> Quoting Ville Syrjälä (2024-09-23 16:23:27-03:00)
> >On Mon, Sep 23, 2024 at 04:02:54PM -0300, Gustavo Sousa wrote:
> >> Tracepoints that display frame and scanline counters for all pipes were
> >> added with commit 1489bba82433 ("drm/i915: Add cxsr toggle tracepoint")
> >> and commit 0b2599a43ca9 ("drm/i915: Add pipe enable/disable
> >> tracepoints"). At that time, we only had pipes A, B and C. Now that we
> >> can also have pipe D, the TP_printk() calls are missing it.
> >> 
> >> As a quick and dirty fix for that, let's define two common macros to be
> >> used for the format and values respectively, and also ensure we raise a
> >> build bug if more pipes are added to enum pipe.
> >> 
> >> In the future, we should probably have a way of printing information for
> >> available pipes only.
> >> 
> >> Cc: Matt Roper <matthew.d.roper@intel.com>
> >> Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
> >> ---
> >>  .../drm/i915/display/intel_display_trace.h    | 43 +++++++++++++------
> >>  1 file changed, 29 insertions(+), 14 deletions(-)
> >> 
> >> diff --git a/drivers/gpu/drm/i915/display/intel_display_trace.h b/drivers/gpu/drm/i915/display/intel_display_trace.h
> >> index eec9aeddad96..9bd8f1e505b0 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_display_trace.h
> >> +++ b/drivers/gpu/drm/i915/display/intel_display_trace.h
> >> @@ -31,6 +31,29 @@
> >>  #define _TRACE_PIPE_A        0
> >>  #define _TRACE_PIPE_B        1
> >>  #define _TRACE_PIPE_C        2
> >> +#define _TRACE_PIPE_D        3
> >> +
> >> +/*
> >> + * FIXME: Several TP_printk() calls below display frame and scanline numbers for
> >> + * all possible pipes (regardless of whether they are available) and that is
> >> + * done with a constant format string. A better approach would be to generate
> >> + * that info dynamically based on available pipes, but, while we do not have
> >> + * that implemented yet, let's assert that the constant format string indeed
> >> + * covers all possible pipes.
> >> + */
> >> +static_assert(I915_MAX_PIPES - 1 == _TRACE_PIPE_D);
> >> +
> >> +#define _PIPES_FRAME_AND_SCANLINE_FMT                \
> >> +        "pipe A: frame=%u, scanline=%u"                \
> >> +        ", pipe B: frame=%u, scanline=%u"        \
> >> +        ", pipe C: frame=%u, scanline=%u"        \
> >> +        ", pipe D: frame=%u, scanline=%u"
> >
> >Hmm. We have a lot of tracpoints that just print these for a single
> >pipe. Is there any decent way to make this macro just for one pipe,
> >and then resuse it for all the tracepoints whether they trace one
> >pipe or all of them?
> 
> Maybe what we could do is to have a local struct pipe_counters type
> and have _PIPE_COUNTERS_FMT and _PIPE_COUNTERS_VALUES for it. Then they
> could be used here as well as for the single-pipe cases.

Can we use structs here or would that confuse trace-cmd as well?

-- 
Ville Syrjälä
Intel