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From: Florian Fainelli <>
To: Geert Uytterhoeven <>,
	Sergei Shtylyov <>,
	"David S . Miller" <>,
	Jakub Kicinski <>
Cc: Andrew Lunn <>,
	Oleksij Rempel <>,
	Philippe Schenker <>,
	Heiner Kallweit <>,
	Russell King <>,
	Kazuya Mizuguchi <>,
	Grygorii Strashko <>,
	Wolfram Sang <>,,,
Subject: Re: [PATCH RFT] ravb: Mask PHY mode to avoid inserting delays twice
Date: Fri, 29 May 2020 08:45:43 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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 <>

Reviewed-by: Florian Fainelli <>

  parent reply	other threads:[~2020-05-29 15:45 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-29 12:25 [PATCH RFT] ravb: Mask PHY mode to avoid inserting delays twice Geert Uytterhoeven
2020-05-29 14:28 ` Andrew Lunn
2020-05-29 15:45 ` Florian Fainelli [this message]
2020-05-31  4:51 ` David Miller
2020-05-31 17:30   ` Sergei Shtylyov

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