| Message ID | 20200418000355.804617-4-andrew@lunn.ch |
|---|---|
| State | Superseded |
| Delegated to: | David Miller |
| Headers | show |
| Series | FEC MDIO speedups | expand |
Hi Andrew, On 4/17/2020 5:03 PM, Andrew Lunn wrote: > An MDIO transaction normally starts with 32 1s as a preamble. However > not all devices requires such a preamble. Add a device tree property > which allows the preamble to be suppressed. This will half the size of > the MDIO transaction, allowing faster transactions. > > Suggested-by: Chris Healy <Chris.Healy@zii.aero> > Signed-off-by: Andrew Lunn <andrew@lunn.ch> > --- > Documentation/devicetree/bindings/net/mdio.yaml | 4 ++++ > drivers/net/ethernet/freescale/fec_main.c | 9 ++++++++- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/Documentation/devicetree/bindings/net/mdio.yaml b/Documentation/devicetree/bindings/net/mdio.yaml > index bcd457c54cd7..41ed4019f8ca 100644 > --- a/Documentation/devicetree/bindings/net/mdio.yaml > +++ b/Documentation/devicetree/bindings/net/mdio.yaml > @@ -43,6 +43,10 @@ properties: > description: > Desired MDIO bus clock frequency in Hz. > > + suppress-preamble: > + description: The 32 bit preamble should be suppressed. > + type: boolean This is a property of the MDIO device node and the MDIO bus controller as well, so I would assume that it has to be treated a little it like the 'broken-turn-around' property and it would have to be a bitmask per MDIO device address that is set/clear depending on what the device support. If it is set for the device and your controller supports it, then you an suppress preamble.
> This is a property of the MDIO device node and the MDIO bus controller as > well, so I would assume that it has to be treated a little it like the > 'broken-turn-around' property and it would have to be a bitmask per MDIO > device address that is set/clear depending on what the device support. If it > is set for the device and your controller supports it, then you an suppress > preamble. Again, i don't see how this can work. You need all the devices on the bus to support preamble suppression, otherwise you cannot use it. As with a maximum clock frequency, we could add the complexity to check as bus scan time that all devices have the necessary property, but i don't think it brings anything. Andrew
On 4/18/2020 7:27 AM, Andrew Lunn wrote: >> This is a property of the MDIO device node and the MDIO bus controller as >> well, so I would assume that it has to be treated a little it like the >> 'broken-turn-around' property and it would have to be a bitmask per MDIO >> device address that is set/clear depending on what the device support. If it >> is set for the device and your controller supports it, then you an suppress >> preamble. > > Again, i don't see how this can work. You need all the devices on the > bus to support preamble suppression, otherwise you cannot use it. As > with a maximum clock frequency, we could add the complexity to check > as bus scan time that all devices have the necessary property, but i > don't think it brings anything. With your current patch I can define 'suppress-preamble' for the FEC MDIO node, and if there is at least one device on the bus that does not support preamble suppression, they are not going to work, so if nothing else you need to intersect between the device capability and the MDIO bus controller capability. Same comments as patch #2 about we could approach this.
On 4/17/2020 5:03 PM, Andrew Lunn wrote: > An MDIO transaction normally starts with 32 1s as a preamble. However > not all devices requires such a preamble. Add a device tree property > which allows the preamble to be suppressed. This will half the size of > the MDIO transaction, allowing faster transactions. > > Suggested-by: Chris Healy <Chris.Healy@zii.aero> > Signed-off-by: Andrew Lunn <andrew@lunn.ch> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
diff --git a/Documentation/devicetree/bindings/net/mdio.yaml b/Documentation/devicetree/bindings/net/mdio.yaml index bcd457c54cd7..41ed4019f8ca 100644 --- a/Documentation/devicetree/bindings/net/mdio.yaml +++ b/Documentation/devicetree/bindings/net/mdio.yaml @@ -43,6 +43,10 @@ properties: description: Desired MDIO bus clock frequency in Hz. + suppress-preamble: + description: The 32 bit preamble should be suppressed. + type: boolean + patternProperties: "^ethernet-phy@[0-9a-f]+$": type: object diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c index 28ef0abfa660..3404e085c657 100644 --- a/drivers/net/ethernet/freescale/fec_main.c +++ b/drivers/net/ethernet/freescale/fec_main.c @@ -2064,6 +2064,7 @@ static int fec_enet_mii_init(struct platform_device *pdev) static struct mii_bus *fec0_mii_bus; struct net_device *ndev = platform_get_drvdata(pdev); struct fec_enet_private *fep = netdev_priv(ndev); + bool suppress_preamble = false; struct device_node *node; int err = -ENXIO; u32 mii_speed, holdtime; @@ -2097,8 +2098,11 @@ static int fec_enet_mii_init(struct platform_device *pdev) bus_freq = 2500000; /* 2.5MHz by default */ node = of_get_child_by_name(pdev->dev.of_node, "mdio"); - if (node) + if (node) { of_property_read_u32(node, "clock-frequency", &bus_freq); + suppress_preamble = of_property_read_bool(node, + "suppress-preamble"); + } /* * Set MII speed (= clk_get_rate() / 2 * phy_speed) @@ -2135,6 +2139,9 @@ static int fec_enet_mii_init(struct platform_device *pdev) fep->phy_speed = mii_speed << 1 | holdtime << 8; + if (suppress_preamble) + fep->phy_speed |= BIT(7); + writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED); /* Clear any pending transaction complete indication */
An MDIO transaction normally starts with 32 1s as a preamble. However not all devices requires such a preamble. Add a device tree property which allows the preamble to be suppressed. This will half the size of the MDIO transaction, allowing faster transactions. Suggested-by: Chris Healy <Chris.Healy@zii.aero> Signed-off-by: Andrew Lunn <andrew@lunn.ch> --- Documentation/devicetree/bindings/net/mdio.yaml | 4 ++++ drivers/net/ethernet/freescale/fec_main.c | 9 ++++++++- 2 files changed, 12 insertions(+), 1 deletion(-)