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Date: Fri, 29 May 2020 08:45:43 -0700 From: Florian Fainelli <f.fainelli@...il.com> To: Geert Uytterhoeven <geert+renesas@...der.be>, Sergei Shtylyov <sergei.shtylyov@...entembedded.com>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org> Cc: Andrew Lunn <andrew@...n.ch>, Oleksij Rempel <linux@...pel-privat.de>, Philippe Schenker <philippe.schenker@...adex.com>, Heiner Kallweit <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>, Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>, Grygorii Strashko <grygorii.strashko@...com>, Wolfram Sang <wsa+renesas@...g-engineering.com>, netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH RFT] ravb: Mask PHY mode to avoid inserting delays twice On 5/29/2020 5:25 AM, Geert Uytterhoeven wrote: > Until recently, the Micrel KSZ9031 PHY driver ignored any PHY mode > ("RGMII-*ID") settings, but used the hardware defaults, augmented by > explicit configuration of individual skew values using the "*-skew-ps" > DT properties. The lack of PHY mode support was compensated by the > EtherAVB MAC driver, which configures TX and/or RX internal delay > itself, based on the PHY mode. > > However, now the KSZ9031 driver has gained PHY mode support, delays may > be configured twice, causing regressions. E.g. on the Renesas > Salvator-X board with R-Car M3-W ES1.0, TX performance dropped from ca. > 400 Mbps to 0.1-0.3 Mbps, as measured by nuttcp. > > As internal delay configuration supported by the KSZ9031 PHY is too > limited for some use cases, the ability to configure MAC internal delay > is deemed useful and necessary. Hence a proper fix would involve > splitting internal delay configuration in two parts, one for the PHY, > and one for the MAC. However, this would require adding new DT > properties, thus breaking DTB backwards-compatibility. > > Hence fix the regression in a backwards-compatibility way, by letting > the EtherAVB driver mask the PHY mode when it has inserted a delay, to > avoid the PHY driver adding a second delay. This also fixes messages > like: > > Micrel KSZ9031 Gigabit PHY e6800000.ethernet-ffffffff:00: *-skew-ps values should be used only with phy-mode = "rgmii" > > as the PHY no longer sees the original RGMII-*ID mode. > > Solving the issue by splitting configuration in two parts can be handled > in future patches, and would require retaining a backwards-compatibility > mode anyway. > > Fixes: bcf3440c6dd78bfe ("net: phy: micrel: add phy-mode support for the KSZ9031 PHY") > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be> Reviewed-by: Florian Fainelli <f.fainelli@...il.com> -- Florian
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