nfp: abm: don't set negative threshold

Turns out the threshold value is used in signed compares in the FW,
so we should avoid setting the top bit.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/abm/main.h

@@ -4,9 +4,12 @@
 #ifndef __NFP_ABM_H__
 #define __NFP_ABM_H__ 1
 
+#include <linux/bits.h>
 #include <net/devlink.h>
 #include <net/pkt_cls.h>
 
+#define NFP_ABM_LVL_INFINITY		S32_MAX
+
 struct nfp_app;
 struct nfp_net;
 

drivers/net/ethernet/netronome/nfp/abm/qdisc.c

@@ -31,7 +31,7 @@ static void
 nfp_abm_reset_root(struct net_device *netdev, struct nfp_abm_link *alink,
 		   u32 handle, unsigned int qs)
 {
-	__nfp_abm_reset_root(netdev, alink, handle, qs, ~0);
+	__nfp_abm_reset_root(netdev, alink, handle, qs, NFP_ABM_LVL_INFINITY);
 }
 
 static int
@@ -67,7 +67,7 @@ nfp_abm_red_destroy(struct net_device *netdev, struct nfp_abm_link *alink,
 	if (alink->parent == TC_H_ROOT) {
 		nfp_abm_reset_root(netdev, alink, TC_H_ROOT, 0);
 	} else {
-		nfp_abm_ctrl_set_q_lvl(alink, i, ~0);
+		nfp_abm_ctrl_set_q_lvl(alink, i, NFP_ABM_LVL_INFINITY);
 		memset(&alink->qdiscs[i], 0, sizeof(*alink->qdiscs));
 	}
 }
@@ -88,6 +88,12 @@ nfp_abm_red_check_params(struct nfp_abm_link *alink,
 			 opt->parent, opt->handle);
 		return false;
 	}
+	if (opt->set.min > NFP_ABM_LVL_INFINITY) {
+		nfp_warn(cpp, "RED offload failed - threshold too large %d > %d (p:%08x h:%08x)\n",
+			 opt->set.min, NFP_ABM_LVL_INFINITY, opt->parent,
+			 opt->handle);
+		return false;
+	}
 
 	return true;
 }