[PATCH 0/2] net: qcom/emac: ensure that pause frames are enabled

The qcom emac driver experiences significant packet loss (through frame
check sequence errors) if flow control is not enabled and the phy is
not configured to allow pause frames to pass through it.  Therefore, we
need to enable flow control and force the phy to pass pause frames.

Timur Tabi (2):
  net: qcom/emac: configure the external phy to allow pause frames
  [v2] net: qcom/emac: enable flow control if requested

 drivers/net/ethernet/qualcomm/emac/emac-mac.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

Pause frames are used to enable flow control.  A MAC can send and
receive pause frames in order to throttle traffic.  However, the PHY
must be configured to allow those frames to pass through.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Timur Tabi <redacted>
---
 drivers/net/ethernet/qualcomm/emac/emac-mac.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/qualcomm/emac/emac-mac.c b/drivers/net/ethernet/qualcomm/emac/emac-mac.c
index 6fb3bee..70a55dc 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac-mac.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac-mac.c

@@ -1003,6 +1003,12 @@ int emac_mac_up(struct emac_adapter *adpt)
 	writel((u32)~DIS_INT, adpt->base + EMAC_INT_STATUS);
 	writel(adpt->irq.mask, adpt->base + EMAC_INT_MASK);
 
+	/* Enable pause frames.  Without this feature, the EMAC has been shown
+	 * to receive (and drop) frames with FCS errors at gigabit connections.
+	 */
+	adpt->phydev->supported |= SUPPORTED_Pause | SUPPORTED_Asym_Pause;
+	adpt->phydev->advertising |= SUPPORTED_Pause | SUPPORTED_Asym_Pause;
+
 	adpt->phydev->irq = PHY_IGNORE_INTERRUPT;
 	phy_start(adpt->phydev);
 

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

If the PHY has been configured to allow pause frames, then the MAC
should be configured to generate and/or accept those frames.

Signed-off-by: Timur Tabi <redacted>
---

v2: fix calculation when TXFC should be set

 drivers/net/ethernet/qualcomm/emac/emac-mac.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/emac/emac-mac.c b/drivers/net/ethernet/qualcomm/emac/emac-mac.c
index 70a55dc..0b4deb3 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac-mac.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac-mac.c

@@ -575,10 +575,11 @@ void emac_mac_start(struct emac_adapter *adpt)
 
 	mac |= TXEN | RXEN;     /* enable RX/TX */
 
-	/* We don't have ethtool support yet, so force flow-control mode
-	 * to 'full' always.
-	 */
-	mac |= TXFC | RXFC;
+	/* Configure MAC flow control to match the PHY's settings. */
+	if (phydev->pause)
+		mac |= RXFC;
+	if (phydev->pause != phydev->asym_pause)
+		mac |= TXFC;
 
 	/* setup link speed */
 	mac &= ~SPEED_MASK;

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

From: Timur Tabi <redacted>
Date: Mon,  7 Nov 2016 10:51:39 -0600

The qcom emac driver experiences significant packet loss (through frame
check sequence errors) if flow control is not enabled and the phy is
not configured to allow pause frames to pass through it.  Therefore, we
need to enable flow control and force the phy to pass pause frames.

Series applied, thanks.