[PATCH v2 1/2] net: ravb: Always process TX descriptor ring

From: Paul Barker <paul.barker.ct@bp.renesas.com>
To: "Sergey Shtylyov" <s.shtylyov@omp.ru>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>
Cc: Paul Barker <paul.barker.ct@bp.renesas.com>,
	netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 1/2] net: ravb: Always process TX descriptor ring
Date: Tue,  2 Apr 2024 15:53:04 +0100	[thread overview]
Message-ID: <20240402145305.82148-1-paul.barker.ct@bp.renesas.com> (raw)

The TX queue should be serviced each time the poll function is called,
even if the full RX work budget has been consumed. This prevents
starvation of the TX queue when RX bandwidth usage is high.

Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
---
Changes from v1:
  * Use the correct 'Fixes' tag.
  * Call the new variable 'unmask' and drop the unnecessary initializer,
    as requested by Sergey.

 drivers/net/ethernet/renesas/ravb_main.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index d1be030c8848..48803050abdb 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -1324,12 +1324,12 @@ static int ravb_poll(struct napi_struct *napi, int budget)
 	int q = napi - priv->napi;
 	int mask = BIT(q);
 	int quota = budget;
+	bool unmask;
 
 	/* Processing RX Descriptor Ring */
 	/* Clear RX interrupt */
 	ravb_write(ndev, ~(mask | RIS0_RESERVED), RIS0);
-	if (ravb_rx(ndev, &quota, q))
-		goto out;
+	unmask = !ravb_rx(ndev, &quota, q);
 
 	/* Processing TX Descriptor Ring */
 	spin_lock_irqsave(&priv->lock, flags);
@@ -1339,6 +1339,9 @@ static int ravb_poll(struct napi_struct *napi, int budget)
 	netif_wake_subqueue(ndev, q);
 	spin_unlock_irqrestore(&priv->lock, flags);
 
+	if (!unmask)
+		goto out;
+
 	napi_complete(napi);
 
 	/* Re-enable RX/TX interrupts */

base-commit: ea2a1cfc3b2019bdea6324acd3c03606b60d71ad
-- 
2.39.2

