netdev - RE: [PATCH net-next 1/2] net: phy: aquantia: add rate

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Date:   Tue, 28 Jan 2020 07:02:44 +0000
From:   "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "andrew@...n.ch" <andrew@...n.ch>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "ykaukab@...e.de" <ykaukab@...e.de>
Subject: RE: [PATCH net-next 1/2] net: phy: aquantia: add rate_adaptation
 indication

> -----Original Message-----
> From: Florian Fainelli <f.fainelli@...il.com>
> Sent: Monday, January 27, 2020 7:43 PM
> To: Madalin Bucur (OSS) <madalin.bucur@....nxp.com>; davem@...emloft.net
> Cc: andrew@...n.ch; hkallweit1@...il.com; netdev@...r.kernel.org;
> ykaukab@...e.de
> Subject: Re: [PATCH net-next 1/2] net: phy: aquantia: add rate_adaptation
> indication
> 
> On 1/22/20 11:38 PM, Madalin Bucur (OSS) wrote:
> >> -----Original Message-----
> >> From: Florian Fainelli <f.fainelli@...il.com>
> >> Sent: Wednesday, January 22, 2020 7:58 PM
> >> To: Madalin Bucur (OSS) <madalin.bucur@....nxp.com>;
> davem@...emloft.net
> >> Cc: andrew@...n.ch; hkallweit1@...il.com; netdev@...r.kernel.org;
> >> ykaukab@...e.de
> >> Subject: Re: [PATCH net-next 1/2] net: phy: aquantia: add
> rate_adaptation
> >> indication
> >>
> >> On 1/22/20 5:59 AM, Madalin Bucur wrote:
> >>> The AQR PHYs are able to perform rate adaptation between
> >>> the system interface and the line interfaces. When such
> >>> a PHY is deployed, the ethernet driver should not limit
> >>> the modes supported or advertised by the PHY. This patch
> >>> introduces the bit that allows checking for this feature
> >>> in the phy_device structure and its use for the Aquantia
> >>> PHYs.
> >>>
> >>> Signed-off-by: Madalin Bucur <madalin.bucur@....nxp.com>
> >>> ---
> >>>  drivers/net/phy/aquantia_main.c | 3 +++
> >>>  include/linux/phy.h             | 3 +++
> >>>  2 files changed, 6 insertions(+)
> >>>
> >>> diff --git a/drivers/net/phy/aquantia_main.c
> >> b/drivers/net/phy/aquantia_main.c
> >>> index 975789d9349d..36fdd523b758 100644
> >>> --- a/drivers/net/phy/aquantia_main.c
> >>> +++ b/drivers/net/phy/aquantia_main.c
> >>> @@ -209,6 +209,9 @@ static int aqr_config_aneg(struct phy_device
> >> *phydev)
> >>>  	u16 reg;
> >>>  	int ret;
> >>>
> >>> +	/* add here as this is called for all devices */
> >>> +	phydev->rate_adaptation = 1;
> >>
> >> How about introducing a new PHY_SUPPORTS_RATE_ADAPTATION flag and you
> >> set that directly from the phy_driver entry? using the "flags" bitmask
> >> instead of adding another structure member to phy_device?
> >
> > I've looked at the phydev->dev_flags use, it seemed to me that mostly it
> > is used to convey configuration options towards the PHY.
> 
> You read me incorrectly, I am suggesting using the phy_driver::flags
> member, not the phy_device::dev_flags entry, please re-consider your
> position.

Sorry, I was looking at the wrong flags (thinking this is a PHY device feature,
not a PHY driver feature).

I've looked at PHY_IS_INTERNAL as a reference and found it's used like this:

        if (phydrv->flags & PHY_IS_INTERNAL)
                phydev->is_internal = true;

it just gets mirrored in a phy_device bit so I concluded this bit could fit
there just as well, that's how I came up with the current proposal.

There is ample space unused in the phy_driver flags, so I can add the bit there.
Should I add accessors too?

> > Another problem
> > is that it's meaning seems to be opaque,  PHY specific. I wanted to avoid
> > trampling on a certain PHY hardcoded value and I turned my attention to
> > the bit fields in the phy_device. I noticed that there are already 12
> > bits so due to alignment, the added bit is not adding extra size to the
> > struct.
> >
> >>> +
> >>>  	if (phydev->autoneg == AUTONEG_DISABLE)
> >>>  		return genphy_c45_pma_setup_forced(phydev);
> >>>
> >>> diff --git a/include/linux/phy.h b/include/linux/phy.h
> >>> index dd4a91f1feaa..2a5c202333fc 100644
> >>> --- a/include/linux/phy.h
> >>> +++ b/include/linux/phy.h
> >>> @@ -387,6 +387,9 @@ struct phy_device {
> >>>  	/* Interrupts are enabled */
> >>>  	unsigned interrupts:1;
> >>>
> >>> +	/* Rate adaptation in the PHY */
> >>> +	unsigned rate_adaptation:1;
> >>> +
> >>>  	enum phy_state state;
> >>>
> >>>  	u32 dev_flags;
> >>>
> >>
> >>
> >> --
> >> Florian
> 
> 
> --
> Florian