eth: fbnic: Increase FBNIC_QUEUE_SIZE_MIN to 64

On systems with 64K pages, RX queues will be wedged if users set the
descriptor count to the current minimum (16). Fbnic fragments large
pages into 4K chunks, and scales down the ring size accordingly. With
64K pages and 16 descriptors, the ring size mask is 0 and will never
be filled.

32 descriptors is another special case that wedges the RX rings.
Internally, the rings track pages for the head/tail pointers, not page
fragments. So with 32 descriptors, there's only 1 usable page as one
ring slot is kept empty to disambiguate between an empty/full ring.
As a result, the head pointer never advances and the HW stalls after
consuming 16 page fragments.

Fixes: 0cb4c0a ("eth: fbnic: Implement Rx queue alloc/start/stop/free")
Signed-off-by: Dimitri Daskalakis <daskald@meta.com>
Link: https://patch.msgid.link/20260401162848.2335350-1-dimitri.daskalakis1@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: ddaskala

drivers/net/ethernet/meta/fbnic/fbnic_txrx.h

@@ -38,7 +38,7 @@ struct fbnic_net;
 #define FBNIC_MAX_XDPQS			128u
 
 /* These apply to TWQs, TCQ, RCQ */
-#define FBNIC_QUEUE_SIZE_MIN		16u
+#define FBNIC_QUEUE_SIZE_MIN		64u
 #define FBNIC_QUEUE_SIZE_MAX		SZ_64K
 
 #define FBNIC_TXQ_SIZE_DEFAULT		1024