linux-kernel - Re: [PATCH] net: mdio: mdio-bcm-unimac: Delay before first poll

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Message-ID: <c3cc7a9d-d464-48e7-beb7-b90b1abbcfc7@lunn.ch>
Date:   Wed, 13 Dec 2023 11:57:52 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Justin Chen <justin.chen@...adcom.com>
Cc:     netdev@...r.kernel.org, Doug Berger <opendmb@...il.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: mdio: mdio-bcm-unimac: Delay before first poll

On Tue, Dec 12, 2023 at 04:02:49PM -0800, Justin Chen wrote:
> With a clock interval of 400 nsec and a 64 bit transactions (32 bit
> preamble & 16 bit control & 16 bit data), it is reasonable to assume
> the mdio transaction will take 25.6 usec. Add a 30 usec delay before
> the first poll to reduce the chance of a 1000-2000 usec sleep.

#define  MDIO_C45               0

suggests the hardware can do C45? The timing works out different then.
Maybe add a comment by the udelay() that is assumes C22, to give a
clue to somebody who is adding C45 support the delay needs to be
re-evaluated.

	Andrew