linux-kernel - Re: [PATCH v2 2/2] net: phy: realtek: Change TX-delay setting for RGMII modes only

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Message-ID: <CAFBinCC3zG4aBZfob2FqYiytvEAKDUQUZn9GTJYE-3Jn_v0HRA@mail.gmail.com>
Date:   Tue, 7 May 2019 22:09:41 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Serge Semin <Sergey.Semin@...latforms.ru>,
        netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] net: phy: realtek: Change TX-delay setting for
 RGMII modes only

Hi Heiner,

On Tue, May 7, 2019 at 7:37 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> On 06.05.2019 19:21, Martin Blumenstingl wrote:
> > Hi Serge,
> >
> > On Mon, May 6, 2019 at 4:39 PM Serge Semin <fancer.lancer@...il.com> wrote:
> > [...]
> >>> the changes in patch 1 are looking good to me (except that I would use
> >>> phy_modify_paged instead of open-coding it, functionally it's
> >>> identical with what you have already)
> >>>
> >>
> >> Nah, this isn't going to work since the config register is placed on an extension
> >> page. So in order to reach the register first I needed to enable a standard page,
> >> then select an extended page, then modify the register bits.
> > I'm probably missing something here. my understanding about
> > phy_modify_paged is that it is equal to:
> > - select extension page
> > - read register
> > - calculate the new register value
> > - write register
> > - restore the original extension page
> >
> What maybe causes the confusion: Realtek has two kinds of pages.
> First there is the following, let's call it simple page:
> You select a page via register 0x1f and then access the paged register.
>
> Then there are extended pages. First you select a page via register 0x1f,
> then the extended page via register 0x1e, and then the paged register.
I totally missed that, thank you for pointing me in the right direction!
that means I don't have anything obvious to complain about in patch 1.


Regards
Martin