While testing I/O performance on a SolidRun Clearfog Pro (ARMADA A38x) with an SSD (PLEXTOR PX-128M6G-2242) encrypted by GELI AES-CBC, errors were reported on the console/dmesg about running out of TMDA descriptors.

Looking at sys/dev/cesa/cesa.h, the comments seem to focus on network buffers with a maximum size of 1500 bytes while SSD disk I/O in my case would involve 4KB buffers. Without really diving into the rest of the code, I've increased the values in cesa.h and can now operate the SSD with sustained rates ~200MB/s without running out of TDMA descriptors.

There might be better ways to do this but the "diff" below most certainly fixed my issue.

Index: sys/dev/cesa/cesa.h
===================================================================
--- sys/dev/cesa/cesa.h (revision 329554)
+++ sys/dev/cesa/cesa.h (working copy)
@@ -63,8 +63,8 @@
  */
 
 /* Values below are optimized for requests containing about 1.5 kB of data */
-#define CESA_SA_DESC_PER_REQ           2
-#define CESA_TDMA_DESC_PER_REQ         8
+#define CESA_SA_DESC_PER_REQ           (2 * 3)   /* 4KB, not 1.5kB */
+#define CESA_TDMA_DESC_PER_REQ         (8 * 3)   /* 4KB, not 1.5kB */
 
 #define CESA_SA_DESCRIPTORS            (CESA_SA_DESC_PER_REQ * CESA_REQUESTS)
 #define CESA_TDMA_DESCRIPTORS          (CESA_TDMA_DESC_PER_REQ * CESA_REQUESTS)