pipe_crc: Warn if the CRC values is 0xffffffff

This is what we read when the CRC logic in in a powered down well. We
really don't want that to happen.

In theory, it's possible 0xffffffff to be a valid CRC value, so I don't
assert here.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index 2f655a1..5c4bbc5 100644 (file)
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -199,9 +199,14 @@ bool igt_crc_is_null(igt_crc_t *crc)
 {
        int i;
 
-       for (i = 0; i < crc->n_words; i++)
+       for (i = 0; i < crc->n_words; i++) {
+               if (crc->crc[i] == 0xffffffff)
+                       igt_warn("Suspicious CRC: it looks like the CRC "
+                                "read back was from a register in a powered "
+                                "down well\n");
                if (crc->crc[i])
                        return false;
+       }
 
        return true;
 }