+
+       for (i = 0 ; i < count ; i++, data++) {
+               dev_err(dev, ": 0x%02x, %02d, 0x%08llx, 0x%04x, %d, %llu, %llu,
0x%llx",
+                               data->op, data->tag, data->lba, data->sct, data->retries,
+                               data->start_time, data->end_time, data-

quoted

outstanding_reqs);

+               idx = (idx == MAX_CMD_LOGS - 1) ? 0 : idx + 1;
+       }

Maybe just outside of the loop:
idx += count;
idx %= (MAX_CMD_LOGS - 1);