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From:   Yan Markman <ymarkman@marvell.com>
To:     Antoine Tenart <antoine.tenart@bootlin.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "linux@armlinux.org.uk" <linux@armlinux.org.uk>
CC:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "thomas.petazzoni@bootlin.com" <thomas.petazzoni@bootlin.com>,
        "maxime.chevallier@bootlin.com" <maxime.chevallier@bootlin.com>,
        "gregory.clement@bootlin.com" <gregory.clement@bootlin.com>,
        "miquel.raynal@bootlin.com" <miquel.raynal@bootlin.com>,
        Nadav Haklai <nadavh@marvell.com>,
        Stefan Chulski <stefanc@marvell.com>,
        "mw@semihalf.com" <mw@semihalf.com>
Subject: RE: [EXT] [PATCH net-next 07/15] net: mvpp2: fix the computation of
 the RXQs
Thread-Topic: [EXT] [PATCH net-next 07/15] net: mvpp2: fix the computation of
 the RXQs
Thread-Index: AQHUz2kgKPwN26EEkkuIctJYcg+bCKX1UyYw
Date:   Thu, 28 Feb 2019 15:40:50 +0000
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References: <20190228132128.30154-1-antoine.tenart@bootlin.com>
 <20190228132128.30154-8-antoine.tenart@bootlin.com>
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Some real and "potential" functionalities have been shrunk in September-201=
8
on transition from single-big file to the current split driver onto several=
 files.

Regarding the MVPP2_DEFAULT_RXQ
Seems the current variant is flexible, permitting easy customize the config=
uration according to customer's needs.

Regarding the Queue in probe():
Looking into old code there where no2 queue-modes but 3:
enum mv_pp2_queue_distribution_mode {
	MVPP2_QDIST_SINGLE_MODE,
	MVPP2_QDIST_MULTI_MODE,
	MVPP2_SINGLE_RESOURCE_MODE
};
The current   if(MVPP2_QDIST_MULTI_MODE)else is correct also for the MVPP2_=
SINGLE_RESOURCE_MODE,
but new/patched isn't.

Since this patch doesn't change any functionality (right now) but reduces t=
he flexibility I do not see real reason to apply it.

Regards
Yan Markman

-----Original Message-----
From: Antoine Tenart <antoine.tenart@bootlin.com>=20
Sent: Thursday, February 28, 2019 3:21 PM
To: davem@davemloft.net; linux@armlinux.org.uk
Cc: Antoine Tenart <antoine.tenart@bootlin.com>; netdev@vger.kernel.org; li=
nux-kernel@vger.kernel.org; thomas.petazzoni@bootlin.com; maxime.chevallier=
@bootlin.com; gregory.clement@bootlin.com; miquel.raynal@bootlin.com; Nadav=
 Haklai <nadavh@marvell.com>; Stefan Chulski <stefanc@marvell.com>; Yan Mar=
kman <ymarkman@marvell.com>; mw@semihalf.com
Subject: [EXT] [PATCH net-next 07/15] net: mvpp2: fix the computation of th=
e RXQs

External Email

----------------------------------------------------------------------
The patch fixes the computation of RXQs being used by the PPv2 driver, whic=
h is set depending on the PPv2 engine version and the queue mode used. Ther=
e are three cases:

- PPv2.1: 1 RXQ per CPU.
- PPV2.2 with MVPP2_QDIST_MULTI_MODE: 1 RXQ per CPU.
- PPv2.2 with MVPP2_QDIST_SINGLE_MODE: 1 RXQ is shared between the CPUs.

The PPv2 engine supports a maximum of 32 queues per port. This patch adds a=
 check so that we do not overstep this maximum.

It appeared the calculation was broken for PPv2.1 engines since f8c6ba8424b=
0, as PPv2.1 ports ended up with a single RXQ while they needed 4. This pat=
ch fixes it.

Fixes: f8c6ba8424b0 ("net: mvpp2: use only one rx queue per port per CPU")
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
---
 drivers/net/ethernet/marvell/mvpp2/mvpp2.h    |  4 ++--
 .../net/ethernet/marvell/mvpp2/mvpp2_main.c   | 23 ++++++++++++-------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h b/drivers/net/ether=
net/marvell/mvpp2/mvpp2.h
index 17ff330cce5f..687e011de5ef 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h
@@ -549,8 +549,8 @@
 #define MVPP2_MAX_TSO_SEGS		300
 #define MVPP2_MAX_SKB_DESCS		(MVPP2_MAX_TSO_SEGS * 2 + MAX_SKB_FRAGS)
=20
-/* Default number of RXQs in use */
-#define MVPP2_DEFAULT_RXQ		1
+/* Max number of RXQs per port */
+#define MVPP2_PORT_MAX_RXQ		32
=20
 /* Max number of Rx descriptors */
 #define MVPP2_MAX_RXD_MAX		1024
diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/=
ethernet/marvell/mvpp2/mvpp2_main.c
index 24cee6cbe309..9c6200a59910 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
@@ -4062,8 +4062,8 @@ static int mvpp2_multi_queue_vectors_init(struct mvpp=
2_port *port,
 			snprintf(irqname, sizeof(irqname), "hif%d", i);
=20
 		if (queue_mode =3D=3D MVPP2_QDIST_MULTI_MODE) {
-			v->first_rxq =3D i * MVPP2_DEFAULT_RXQ;
-			v->nrxqs =3D MVPP2_DEFAULT_RXQ;
+			v->first_rxq =3D i;
+			v->nrxqs =3D 1;
 		} else if (queue_mode =3D=3D MVPP2_QDIST_SINGLE_MODE &&
 			   i =3D=3D (port->nqvecs - 1)) {
 			v->first_rxq =3D 0;
@@ -4156,8 +4156,7 @@ static int mvpp2_port_init(struct mvpp2_port *port)
 	    MVPP2_MAX_PORTS * priv->max_port_rxqs)
 		return -EINVAL;
=20
-	if (port->nrxqs % MVPP2_DEFAULT_RXQ ||
-	    port->nrxqs > priv->max_port_rxqs || port->ntxqs > MVPP2_MAX_TXQ)
+	if (port->nrxqs > priv->max_port_rxqs || port->ntxqs > MVPP2_MAX_TXQ)
 		return -EINVAL;
=20
 	/* Disable port */
@@ -4778,10 +4777,18 @@ static int mvpp2_port_probe(struct platform_device =
*pdev,
 	}
=20
 	ntxqs =3D MVPP2_MAX_TXQ;
-	if (priv->hw_version =3D=3D MVPP22 && queue_mode =3D=3D MVPP2_QDIST_MULTI=
_MODE)
-		nrxqs =3D MVPP2_DEFAULT_RXQ * num_possible_cpus();
-	else
-		nrxqs =3D MVPP2_DEFAULT_RXQ;
+	if (priv->hw_version =3D=3D MVPP22 && queue_mode =3D=3D MVPP2_QDIST_SINGL=
E_MODE) {
+		nrxqs =3D 1;
+	} else {
+		/* According to the PPv2.2 datasheet and our experiments on
+		 * PPv2.1, RX queues have an allocation granularity of 4 (when
+		 * more than a single one on PPv2.2).
+		 * Round up to nearest multiple of 4.
+		 */
+		nrxqs =3D (num_possible_cpus() + 3) & ~0x3;
+		if (nrxqs > MVPP2_PORT_MAX_RXQ)
+			nrxqs =3D MVPP2_PORT_MAX_RXQ;
+	}
=20
 	dev =3D alloc_etherdev_mqs(sizeof(*port), ntxqs, nrxqs);
 	if (!dev)
--
2.20.1