bnxt: fix bnxt_get_avail_msix() returning negative values

Current net-next/main does not boot for older chipsets e.g. Stratus.

Sample dmesg:
[   11.368315] bnxt_en 0000:02:00.0 (unnamed net_device) (uninitialized): Able to reserve only 0 out of 9 requested RX rings
[   11.390181] bnxt_en 0000:02:00.0 (unnamed net_device) (uninitialized): Unable to reserve tx rings
[   11.438780] bnxt_en 0000:02:00.0 (unnamed net_device) (uninitialized): 2nd rings reservation failed.
[   11.487559] bnxt_en 0000:02:00.0 (unnamed net_device) (uninitialized): Not enough rings available.
[   11.506012] bnxt_en 0000:02:00.0: probe with driver bnxt_en failed with error -12

This is caused by bnxt_get_avail_msix() returning a negative value for
these chipsets not using the new resource manager i.e. !BNXT_NEW_RM.
This in turn causes hwr.cp in __bnxt_reserve_rings() to be set to 0.

In the current call stack, __bnxt_reserve_rings() is called from
bnxt_set_dflt_rings() before bnxt_init_int_mode(). Therefore,
bp->total_irqs is always 0 and for !BNXT_NEW_RM bnxt_get_avail_msix()
always returns a negative number.

Historically, MSIX vectors were requested by the RoCE driver during
run-time and bnxt_get_avail_msix() was used for this purpose. Today,
RoCE MSIX vectors are statically allocated. bnxt_get_avail_msix() should
only be called for the BNXT_NEW_RM() case to reserve the MSIX ahead of
time for RoCE use.

bnxt_get_avail_msix() is also be simplified to handle the BNXT_NEW_RM()
case only.

Fixes: d630624e ("bnxt_en: Utilize ulp client resources if RoCE is not registered")
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20240502203757.3761827-1-dw@davidwei.ukSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -7469,6 +7469,8 @@ static bool bnxt_rings_ok(struct bnxt *bp, struct bnxt_hw_rings *hwr)
 	       hwr->stat && (hwr->cp_p5 || !(bp->flags & BNXT_FLAG_CHIP_P5_PLUS));
 }
 
+static int bnxt_get_avail_msix(struct bnxt *bp, int num);
+
 static int __bnxt_reserve_rings(struct bnxt *bp)
 {
 	struct bnxt_hw_rings hwr = {0};
@@ -7481,7 +7483,7 @@ static int __bnxt_reserve_rings(struct bnxt *bp)
 	if (!bnxt_need_reserve_rings(bp))
 		return 0;
 
-	if (!bnxt_ulp_registered(bp->edev)) {
+	if (BNXT_NEW_RM(bp) && !bnxt_ulp_registered(bp->edev)) {
 		ulp_msix = bnxt_get_avail_msix(bp, bp->ulp_num_msix_want);
 		if (!ulp_msix)
 			bnxt_set_ulp_stat_ctxs(bp, 0);
@@ -10484,19 +10486,10 @@ unsigned int bnxt_get_avail_stat_ctxs_for_en(struct bnxt *bp)
 	return bnxt_get_max_func_stat_ctxs(bp) - bnxt_get_func_stat_ctxs(bp);
 }
 
-int bnxt_get_avail_msix(struct bnxt *bp, int num)
+static int bnxt_get_avail_msix(struct bnxt *bp, int num)
 {
-	int max_cp = bnxt_get_max_func_cp_rings(bp);
 	int max_irq = bnxt_get_max_func_irqs(bp);
 	int total_req = bp->cp_nr_rings + num;
-	int max_idx, avail_msix;
-
-	max_idx = bp->total_irqs;
-	if (!(bp->flags & BNXT_FLAG_CHIP_P5_PLUS))
-		max_idx = min_t(int, bp->total_irqs, max_cp);
-	avail_msix = max_idx - bp->cp_nr_rings;
-	if (!BNXT_NEW_RM(bp) || avail_msix >= num)
-		return avail_msix;
 
 	if (max_irq < total_req) {
 		num = max_irq - bp->cp_nr_rings;
@@ -10629,7 +10622,7 @@ int bnxt_reserve_rings(struct bnxt *bp, bool irq_re_init)
 	if (!bnxt_need_reserve_rings(bp))
 		return 0;
 
-	if (!bnxt_ulp_registered(bp->edev)) {
+	if (BNXT_NEW_RM(bp) && !bnxt_ulp_registered(bp->edev)) {
 		int ulp_msix = bnxt_get_avail_msix(bp, bp->ulp_num_msix_want);
 
 		if (ulp_msix > bp->ulp_num_msix_want)

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -2738,7 +2738,6 @@ unsigned int bnxt_get_max_func_stat_ctxs(struct bnxt *bp);
 unsigned int bnxt_get_avail_stat_ctxs_for_en(struct bnxt *bp);
 unsigned int bnxt_get_max_func_cp_rings(struct bnxt *bp);
 unsigned int bnxt_get_avail_cp_rings_for_en(struct bnxt *bp);
-int bnxt_get_avail_msix(struct bnxt *bp, int num);
 int bnxt_reserve_rings(struct bnxt *bp, bool irq_re_init);
 void bnxt_tx_disable(struct bnxt *bp);
 void bnxt_tx_enable(struct bnxt *bp);