netdev - [PATCH net] ibmvnic: Fall back to 16 H_SEND_SUB_CRQ

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Date:   Mon, 27 Apr 2020 12:33:43 -0500
From:   Juliet Kim <julietk@...ux.vnet.ibm.com>
To:     netdev@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, julietk@...ux.vnet.ibm.com,
        tlfalcon@...ux.vnet.ibm.com
Subject: [PATCH net] ibmvnic: Fall back to 16 H_SEND_SUB_CRQ_INDIRECT entries with old FW

The maximum entries for H_SEND_SUB_CRQ_INDIRECT has increased on
some platforms from 16 to 128. If Live Partition Mobility is used
to migrate a running OS image from a newer source platform to an
older target platform, then H_SEND_SUB_CRQ_INDIRECT will fail with
H_PARAMETER if 128 entries are queued.

Fix this by falling back to 16 entries if H_PARAMETER is returned
from the hcall().

Signed-off-by: Juliet Kim <julietk@...ux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 4bd33245bad6..b66c2f26a427 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1656,6 +1656,17 @@ static netdev_tx_t ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		lpar_rc = send_subcrq_indirect(adapter, handle_array[queue_num],
 					       (u64)tx_buff->indir_dma,
 					       (u64)num_entries);
+
+		/* Old firmware accepts max 16 num_entries */
+		if (lpar_rc == H_PARAMETER && num_entries > 16) {
+			tx_crq.v1.n_crq_elem = 16;
+			tx_buff->num_entries = 16;
+			lpar_rc = send_subcrq_indirect(adapter,
+						       handle_array[queue_num],
+						       (u64)tx_buff->indir_dma,
+						       16);
+		}
+
 		dma_unmap_single(dev, tx_buff->indir_dma,
 				 sizeof(tx_buff->indir_arr), DMA_TO_DEVICE);
 	} else {
-- 
2.18.1