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

3 messages, 3 authors, 2016-11-04 · open the first message on its own page

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

From: Måns Rullgård <hidden>
Date: 2016-11-04 15:18:24

Sebastian Frias [off-list ref] writes:
The delay can be applied at PHY or MAC level, but since
PHY drivers will apply the delay at PHY level when using
one of the "internal delay" declinations of RGMII mode
(like PHY_INTERFACE_MODE_RGMII_TXID), applying it again
at MAC level causes issues.
The Broadcom GENET driver does the same thing.
quoted hunk
Signed-off-by: Sebastian Frias <redacted>
---
 drivers/net/ethernet/aurora/nb8800.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/aurora/nb8800.c b/drivers/net/ethernet/aurora/nb8800.c
index b59aa35..d2855c9 100644
--- a/drivers/net/ethernet/aurora/nb8800.c
+++ b/drivers/net/ethernet/aurora/nb8800.c
@@ -1282,7 +1282,7 @@ static int nb8800_tangox_init(struct net_device *dev)
 		break;

 	case PHY_INTERFACE_MODE_RGMII_TXID:
-		pad_mode = PAD_MODE_RGMII | PAD_MODE_GTX_CLK_DELAY;
+		pad_mode = PAD_MODE_RGMII;
 		break;

 	default:
-- 
1.7.11.2
If this change is correct (and I'm not convinced it is), that case
should be merged with the one above it and PHY_INTERFACE_MODE_RGMII_RXID
added as well.

-- 
Måns Rullgård

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

From: Sebastian Frias <hidden>
Date: 2016-11-04 15:36:54

Hi Måns,

On 11/04/2016 04:18 PM, Måns Rullgård wrote:
Sebastian Frias [off-list ref] writes:
quoted
The delay can be applied at PHY or MAC level, but since
PHY drivers will apply the delay at PHY level when using
one of the "internal delay" declinations of RGMII mode
(like PHY_INTERFACE_MODE_RGMII_TXID), applying it again
at MAC level causes issues.
The Broadcom GENET driver does the same thing.
Well, I don't know who uses that driver, or why they did it that way.

However, with the current code and DT bindings, if one requires
the delay, phy-connection-type="rgmii-txid" must be set.

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.

I can see how to do that in another patch set.
quoted
Signed-off-by: Sebastian Frias <redacted>
---
 drivers/net/ethernet/aurora/nb8800.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/aurora/nb8800.c b/drivers/net/ethernet/aurora/nb8800.c
index b59aa35..d2855c9 100644
--- a/drivers/net/ethernet/aurora/nb8800.c
+++ b/drivers/net/ethernet/aurora/nb8800.c
@@ -1282,7 +1282,7 @@ static int nb8800_tangox_init(struct net_device *dev)
 		break;

 	case PHY_INTERFACE_MODE_RGMII_TXID:
-		pad_mode = PAD_MODE_RGMII | PAD_MODE_GTX_CLK_DELAY;
+		pad_mode = PAD_MODE_RGMII;
 		break;

 	default:
-- 
1.7.11.2
If this change is correct (and I'm not convinced it is), that case
should be merged with the one above it and PHY_INTERFACE_MODE_RGMII_RXID
added as well.
I can do a single patch.

The reason I made two patches was that it was clear what this patch
does, i.e.: do not apply the delay at MAC level, and what the subsequent
patch does, i.e.: handle all RGMII declinations.

Best regards,

Sebastian

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

From: Florian Fainelli <f.fainelli@gmail.com>
Date: 2016-11-04 16:28:57


On 11/04/2016 08:36 AM, Sebastian Frias wrote:
Hi Måns,

On 11/04/2016 04:18 PM, Måns Rullgård wrote:
quoted
Sebastian Frias [off-list ref] writes:
quoted
The delay can be applied at PHY or MAC level, but since
PHY drivers will apply the delay at PHY level when using
one of the "internal delay" declinations of RGMII mode
(like PHY_INTERFACE_MODE_RGMII_TXID), applying it again
at MAC level causes issues.
The Broadcom GENET driver does the same thing.
Well, I don't know who uses that driver, or why they did it that way.
I do use this driver and it works for me (tm), although I tested mostly
with Broadcom PHYs and Ethernet switches, rarely with third party PHYs,
but had that too, but all of that is in tree though,
drivers/net/phy/broadcom.com, drivers/net/dsa/b53/ so feel free to
"audit" that part of the code too.

The configuration of the GENET port multiplexer requires us to specify
how we want to align the clock and data, if we don't do that, and the
PHY is also not agreeing with how its own delays should be configured,
mayhem ensues, ranging from occasional transmit success, to high rates
of CRC/FCS errors in best cases.

I did verify that the settings were correct using a scope FWIW.
However, with the current code and DT bindings, if one requires
the delay, phy-connection-type="rgmii-txid" must be set.
Yes, and we would set it correctly for our Broadcom reference boards
using this driver.
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.
I can see how to do that in another patch set.
quoted
quoted
Signed-off-by: Sebastian Frias <redacted>
---
 drivers/net/ethernet/aurora/nb8800.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/aurora/nb8800.c b/drivers/net/ethernet/aurora/nb8800.c
index b59aa35..d2855c9 100644
--- a/drivers/net/ethernet/aurora/nb8800.c
+++ b/drivers/net/ethernet/aurora/nb8800.c
@@ -1282,7 +1282,7 @@ static int nb8800_tangox_init(struct net_device *dev)
 		break;

 	case PHY_INTERFACE_MODE_RGMII_TXID:
-		pad_mode = PAD_MODE_RGMII | PAD_MODE_GTX_CLK_DELAY;
+		pad_mode = PAD_MODE_RGMII;
 		break;

 	default:
-- 
1.7.11.2
If this change is correct (and I'm not convinced it is), that case
should be merged with the one above it and PHY_INTERFACE_MODE_RGMII_RXID
added as well.
I can do a single patch.

The reason I made two patches was that it was clear what this patch
does, i.e.: do not apply the delay at MAC level, and what the subsequent
patch does, i.e.: handle all RGMII declinations.

Best regards,

Sebastian
-- 
Florian
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help