linux-kernel - Re: [PATCH 2/3] net: phy: realtek: Enable accessing RTL8211E extension pages

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Date:   Tue, 2 Jul 2019 08:07:57 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Matthias Kaehlcke <mka@...omium.org>, Andrew Lunn <andrew@...n.ch>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 2/3] net: phy: realtek: Enable accessing RTL8211E
 extension pages

On 02.07.2019 02:09, Matthias Kaehlcke wrote:
> On Mon, Jul 01, 2019 at 11:09:02PM +0200, Andrew Lunn wrote:
>> On Mon, Jul 01, 2019 at 10:37:16PM +0200, Heiner Kallweit wrote:
>>> On 01.07.2019 22:02, Andrew Lunn wrote:
>>>> On Mon, Jul 01, 2019 at 12:52:24PM -0700, Matthias Kaehlcke wrote:
>>>>> The RTL8211E has extension pages, which can be accessed after
>>>>> selecting a page through a custom method. Add a function to
>>>>> modify bits in a register of an extension page and a few
>>>>> helpers for dealing with ext pages.
>>>>>
>>>>> rtl8211e_modify_ext_paged() and rtl821e_restore_page() are
>>>>> inspired by their counterparts phy_modify_paged() and
>>>>> phy_restore_page().
>>>>
>>>> Hi Matthias
>>>>
>>>> While an extended page is selected, what happens to the normal
>>>> registers in the range 0-0x1c? Are they still accessible?
>>>>
>>> AFAIK: no
>>
>> This it would be better to make use of the core paged access support,
>> so that locking is done correctly.
> 
> Do I understand correctly that this would involve assigning
> .read/write_page and use phy_select_page() and phy_restore_page()?
> 
> Besides the benefit of locking this would also result in less code and
> we could get rid of the custom _restore_page().
> 
Interestingly certain Realtek PHY's (incl. RTL8211E) support two paging
mechanisms.

1. Normal paging (set reg 0x1f to page number) - set by core paging
2. Extended pages (set reg 0x1f to 7, and reg 0x1e to ext. page number)

Newer Realtek PHY's use normal paging only.