linux-kernel - Re: [PATCH net-next v3 4/6] net: phy: microchip

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Date:   Fri, 26 May 2023 09:14:26 +0200
From:   Ramón Nordin Rodriguez 
        <ramon.nordin.rodriguez@...roamp.se>
To:     Parthiban.Veerasooran@...rochip.com
Cc:     andrew@...n.ch, hkallweit1@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Horatiu.Vultur@...rochip.com,
        Woojung.Huh@...rochip.com, Nicolas.Ferre@...rochip.com,
        Thorsten.Kummermehr@...rochip.com
Subject: Re: [PATCH net-next v3 4/6] net: phy: microchip_t1s: fix reset
 complete status handling

On Fri, May 26, 2023 at 06:00:08AM +0000, Parthiban.Veerasooran@...rochip.com wrote:
> Hi Ramon,
> >> +     /* Read STS2 register and check for the Reset Complete status to do the
> >> +      * init configuration. If the Reset Complete is not set, wait for 5us
> >> +      * and then read STS2 register again and check for Reset Complete status.
> >> +      * Still if it is failed then declare PHY reset error or else proceed
> >> +      * for the PHY initial register configuration.
> >> +      */
> > 
> > This comment explains exactly what the code does, which is also obvious
> > from reading the code. A meaningful comment would be explaining why the
> > state can change 5us later.
> > 
> As per design, LAN867x reset to be completed by 3us. Just for a safer 
> side it is recommended to use 5us. With the assumption of more than 3us 
> completion, the first read checks for the Reset Complete. If the 
> config_init is more faster, then once again checks for it after 5us.
> 
> As you mentioned, can we remove the existing block comment as it 
> explains the code and add the above comment to explain 5us delay.
> What is your opinion on this proposal?
> 
> Best Regards,
> Parthiban V
> 

I'd suggest the following
/*The chip completes a reset in 3us, we might get here earlier than that,
as an added margin we'll conditionally sleep 5us*/