linux-kernel - Re: [PATCH 1/2] net: ethernet: nb8800: Do not apply TX delay at MAC level

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Date:   Wed, 9 Nov 2016 14:02:36 +0100
From:   Sebastian Frias <sf84@...oste.net>
To:     Måns Rullgård <mans@...sr.com>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, Mason <slash.tmp@...e.fr>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH 1/2] net: ethernet: nb8800: Do not apply TX delay at MAC
 level

On 11/04/2016 05:49 PM, Måns Rullgård wrote:
>>> But when doing so, both the Atheros 8035 and the Aurora NB8800 drivers
>>> will apply the delay.
>>>
>>> I think a better way of dealing with this is that both, PHY and MAC
>>> drivers exchange information so that the delay is applied only once.
>>
>> Exchange what information? The PHY device interface (phydev->interface)
>> conveys the needed information for both entities.
> 
> There doesn't seem to be any consensus among the drivers regarding where
> the delay should be applied.  Since only a few drivers, MAC or PHY, act
> on this property, most combinations still work by chance.  It is common
> for boards to set the delay at the PHY using external config pins so no
> software setup is required (although I have one Sigma based board that
> gets this wrong).  I suspect if drivers/net/ethernet/broadcom/genet were
> used with one of the four PHY drivers that also set the delay based on
> this DT property, things would go wrong.
> 

Exactly, what about a patch like (I can make a formal submission, even
merge it with the patch discussed in this thread, consider this a RFC):

diff --git a/drivers/net/ethernet/aurora/nb8800.c b/drivers/net/ethernet/aurora/nb8800.c
index fba2699..4217ff4 100644
--- a/drivers/net/ethernet/aurora/nb8800.c
+++ b/drivers/net/ethernet/aurora/nb8800.c
@@ -1283,6 +1283,10 @@ static int nb8800_tangox_init(struct net_device *dev)
 	case PHY_INTERFACE_MODE_RGMII_RXID:
 	case PHY_INTERFACE_MODE_RGMII_TXID:
 		pad_mode = PAD_MODE_RGMII;
+
+		if ((dev->phydev->flags & PHY_SUPPORTS_TXID) == 0)
+			pad_mode |= PAD_MODE_GTX_CLK_DELAY;
+
 		break;
 
 	default:
diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
index 2e0c759..5eddb04 100644
--- a/drivers/net/phy/at803x.c
+++ b/drivers/net/phy/at803x.c
@@ -426,7 +426,9 @@ static int at803x_aneg_done(struct phy_device *phydev)
 	.suspend		= at803x_suspend,
 	.resume			= at803x_resume,
 	.features		= PHY_GBIT_FEATURES,
-	.flags			= PHY_HAS_INTERRUPT,
+	.flags			= PHY_HAS_INTERRUPT |
+				  PHY_SUPPORTS_RXID |
+				  PHY_SUPPORTS_TXID,
 	.config_aneg		= genphy_config_aneg,
 	.read_status		= genphy_read_status,
 	.ack_interrupt		= at803x_ack_interrupt,
diff --git a/include/linux/phy.h b/include/linux/phy.h
index e7e1fd3..0f0b17e 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -61,6 +61,8 @@
 #define PHY_HAS_INTERRUPT	0x00000001
 #define PHY_HAS_MAGICANEG	0x00000002
 #define PHY_IS_INTERNAL		0x00000004
+#define PHY_SUPPORTS_RXID       0x00000008
+#define PHY_SUPPORTS_TXID       0x00000010
 #define MDIO_DEVICE_IS_PHY	0x80000000
 
 /* Interface Mode definitions */