On 11/10/2016 03:46 PM, Timur Tabi wrote:
> Instead of having individual PHY drivers set the SUPPORTED_Pause and
> SUPPORTED_Asym_Pause flags, phylib itself should set those flags.
> During autonegotiation, the PHYs will determine whether to enable
> pause frame support.
>
> Pause frames are a feature that is supported by the MAC. It is the MAC
> that generates the frames and that processes them. The PHY can only be
> configured to allow them to pass through.
>
> So the new process is:
>
> 1) Phylib sets the SUPPORTED_Pause and SUPPORTED_AsymPause bits in
> phydev->supported. This indicates that the PHY supports pause frames.
>
> 2) The MAC driver checks phydev->supported before it calls phy_start().
> If (SUPPORTED_Pause | SUPPORTED_AsymPause) is set, then the MAC driver
> sets those bits in phydev->advertising, if it wants to enable pause
> frame support.
>
> 3) When the link state changes, the MAC driver checks phydev->pause and
> phydev->asym_pause, If the bits are set, then it enables the corresponding
> features in the MAC. The algorithm is:
>
> if (phydev->pause)
> The MAC should be programmed to receive and honor
> pause frames it receives, i.e. enable receive flow control.
>
> if (phydev->pause != phydev->asym_pause)
> The MAC should be programmed to transmit pause
> frames when needed, i.e. enable transmit flow control.
>
> Signed-off-by: Timur Tabi <ti...@codeaurora.org>
> ---
> diff --git a/drivers/net/phy/bcm63xx.c b/drivers/net/phy/bcm63xx.c
> index e741bf6..5e9922e 100644
> --- a/drivers/net/phy/bcm63xx.c
> +++ b/drivers/net/phy/bcm63xx.c
> @@ -48,8 +48,7 @@ static int bcm63xx_config_init(struct phy_device *phydev)
> .phy_id = 0x00406000,
> .phy_id_mask = 0xfffffc00,
> .name = "Broadcom BCM63XX (1)",
> - /* ASYM_PAUSE bit is marked RO in datasheet, so don't cheat */
> - .features = (PHY_BASIC_FEATURES | SUPPORTED_Pause),
> + .features = PHY_BASIC_FEATURES,
Humm that's actually a pretty important piece of information here that
we are going to lose if we unconditionally move the setting of the
SUPPORTED_Pause/Asym_Pause settings into the core. I don't have the HW
in a state where I could try a mainline kernel, but I suspect that the
following could happen though:
- we would try to set the SUPPORTED_AsymPause bit, and it would not be
taken into account, since the bit is RO
- the auto-negotiation results should still show up as symmetric pause
being supported only
- the driver would properly react to that
NB: this also applies to drivers/net/phy/ste10Xp.c.
So maybe, for theses drivers specifically, what we can do, is preserve
the entry as-is, to convey that only symmetric Pause frames can be
advertised, and have the logic in PHYLIB do something like this
(pseudo-code):
if (!(drv->features & (SUPPORTED_Pause | SUPPORTED_AsymPause))
phydev->supported |= SUPPORTED_Pause | SUPPORTED_AsymPause;
else if ((drv->features & (SUPPORTED_Pause) && (!(drv->features &
(SUPPORTED_AsymPause)))
phydev->supported |= SUPPORTED_Pause;
(there may be more efficient ways to do this of course).
--
Florian
