[Intel-gfx] [PATCH v3] drm/i915: Show HWSP in intel_engine_dump()

[Chris Wilson]

Looking at a CI failure with an ominous line of
[  362.550715] hangcheck current seqno ffffff6b, last ffffff8c, hangcheck ffffff6b [6016 ms], inflight 118
with no apparent cause for the seqno to be negative, left me wondering
if someone had scribbled over the HWSP. So include the HWSP in the
engine dump to see if there are more signs of random scribbling.

v2: Fix row pointer, i is now incremented by 8 so doesn't need scaling
by 8, and we don't need to keep volatile here as the status_page isn't
marked up as volatile itself.
v3: Use hexdump, with suppression of identical lines. (Tvrtko)
    Which results in

HWSP:
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
*
00000040 00000001 00000000 00000018 00000002 00000001 00000000 00000018 00000000
00000060 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000003
00000080 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
*
000000c0 00000002 00000000 00000000 00000000 00000000 00000000 00000000 00000000
000000e0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
*

  instead of 128 lines of mostly 0s.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com> #v2
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 9856e24c7c43..eabd9cee6032 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1667,6 +1667,31 @@ static void print_request(struct drm_printer *m,
 		   rq->timeline->common->name);
 }
 
+static void hexdump(struct drm_printer *m, const void *buf, size_t len)
+{
+	const size_t rowsize = 8 * sizeof(u32);
+	char line[128];
+	const void *prev = NULL;
+	size_t row;
+	bool skip = false;
+
+	for (row = 0; row < len; row += rowsize) {
+		if (prev && !memcmp(prev, buf + row, rowsize)) {
+			if (!skip) {
+				drm_printf(m, "*\n");
+				skip = true;
+			}
+			continue;
+		}
+
+		hex_dump_to_buffer(buf + row, len - row, rowsize, sizeof(u32),
+				   line, sizeof(line), false);
+		drm_printf(m, "%08zx %s\n", row, line);
+		prev = buf + row;
+		skip = false;
+	}
+}
+
 void intel_engine_dump(struct intel_engine_cs *engine,
 		       struct drm_printer *m,
 		       const char *header, ...)
@@ -1869,8 +1894,11 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 				  &engine->irq_posted)),
 		   yesno(test_bit(ENGINE_IRQ_EXECLIST,
 				  &engine->irq_posted)));
+
+	drm_printf(m, "HWSP:\n");
+	hexdump(m, engine->status_page.page_addr, PAGE_SIZE);
+
 	drm_printf(m, "Idle? %s\n", yesno(intel_engine_is_idle(engine)));
-	drm_printf(m, "\n");
 }
 
 static u8 user_class_map[] = {
-- 
2.15.1