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

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Date:   Mon, 6 May 2019 19:21:32 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "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 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

if phy_modify_paged doesn't work for your use-case then ignore my comment.

[...]
> > > (Martin, I also Cc'ed you in this discussion, so if you have anything to
> > > say in this matter, please don't hesitate to comment.)
> > Amlogic boards, such as the Hardkernel Odroid-C1 and Odroid-C2 as well
> > as the Khadas VIM2 use a "RTL8211F" RGMII PHY. I don't know whether
> > there are multiple versions of this PHY. all RTL8211F I have seen so
> > far did behave exactly the same.
> >
> > I also don't know whether the RX delay is configurable (by pin
> > strapping or some register) on RTL8211F PHYs because I don't have
> > access to the datasheet.
> >
> >
> > Martin
>
> Ok. Thanks for the comments. I am sure the RX-delay is configurable at list
> via external RXD pin strapping at the chip powering up procedure. The only
> problem with a way of software to change the setting.
>
> I don't think there is going to be anyone revealing that realtek black boxed
> registers layout anytime soon. So as I see it it's better to leave the
> rtl8211f-part as is for now.
with the RTL8211F I was not sure whether interrupt support was
implemented correctly in the mainline driver.
I asked Realtek for more details:
initially they declined to send me a datasheet and referred me to my
"partner contact" (which I don't have because I'm doing this in my
spare time).
I explained that I am trying to improve the Linux driver for this PHY.
They gave me the relevant bits (about interrupt support) from the
datasheet (I never got the full datasheet though).

if you don't want to touch the RTL8211F part for now then I'm fine
with that as well


Regards
Martin