drm/i915/display: Zero-initialize frame/scanline counts in tracepoints

In an upcoming change, we will also add support for logging
frame/scanline counts for pipe D in relevant tracepoints.

In [1], Matt mentioned the possibility of having garbage in those counts
for pipe D on a platform containing only 3 pipes. Indeed, it has been
verified that the counts for the extra pipe would not be
zero-initialized by the tracing system.

Since it is also possible that the same would happen for a fused-off
pipe, let's go ahead and add the logic to zero-initialize the arrays
now.

[1] https://lore.kernel.org/all/20240918224927.GU5091@mdroper-desk1.amr.corp.intel.com/

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241016135300.21428-3-gustavo.sousa@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_display_trace.h b/drivers/gpu/drm/i915/display/intel_display_trace.h
index e70c015a09a1447aca0909745132d281016d91af..84526f8df75b1ca34516681da7ead2431b76b847 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_display_trace.h
+++ b/drivers/gpu/drm/i915/display/intel_display_trace.h
@@ -9,6 +9,7 @@
 #if !defined(__INTEL_DISPLAY_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ)
 #define __INTEL_DISPLAY_TRACE_H__
 
+#include <linux/string.h>
 #include <linux/string_helpers.h>
 #include <linux/types.h>
 #include <linux/tracepoint.h>
@@ -36,6 +37,10 @@ TRACE_EVENT(intel_pipe_enable,
                           struct intel_display *display = to_intel_display(crtc);
                           struct intel_crtc *it__;
                           __assign_str(dev);
+                          memset(__entry->frame, 0,
+                                 sizeof(__entry->frame[0]) * I915_MAX_PIPES);
+                          memset(__entry->scanline, 0,
+                                 sizeof(__entry->scanline[0]) * I915_MAX_PIPES);
                           for_each_intel_crtc(display->drm, it__) {
                                   __entry->frame[it__->pipe] = intel_crtc_get_vblank_counter(it__);
                                   __entry->scanline[it__->pipe] = intel_get_crtc_scanline(it__);
@@ -65,6 +70,10 @@ TRACE_EVENT(intel_pipe_disable,
                           struct intel_display *display = to_intel_display(crtc);
                           struct intel_crtc *it__;
                           __assign_str(dev);
+                          memset(__entry->frame, 0,
+                                 sizeof(__entry->frame[0]) * I915_MAX_PIPES);
+                          memset(__entry->scanline, 0,
+                                 sizeof(__entry->scanline[0]) * I915_MAX_PIPES);
                           for_each_intel_crtc(display->drm, it__) {
                                   __entry->frame[it__->pipe] = intel_crtc_get_vblank_counter(it__);
                                   __entry->scanline[it__->pipe] = intel_get_crtc_scanline(it__);
@@ -194,6 +203,10 @@ TRACE_EVENT(intel_memory_cxsr,
            TP_fast_assign(
                           struct intel_crtc *crtc;
                           __assign_str(dev);
+                          memset(__entry->frame, 0,
+                                 sizeof(__entry->frame[0]) * I915_MAX_PIPES);
+                          memset(__entry->scanline, 0,
+                                 sizeof(__entry->scanline[0]) * I915_MAX_PIPES);
                           for_each_intel_crtc(display->drm, crtc) {
                                   __entry->frame[crtc->pipe] = intel_crtc_get_vblank_counter(crtc);
                                   __entry->scanline[crtc->pipe] = intel_get_crtc_scanline(crtc);