linux-kernel - Re: Registering IRQ for MT7530 internal PHYs

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Date:   Wed, 30 Dec 2020 08:15:54 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        DENG Qingfang <dqfext@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Marc Zyngier <maz@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Russell King <linux@...linux.org.uk>,
        Sean Wang <sean.wang@...iatek.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>,
        Weijie Gao <weijie.gao@...iatek.com>,
        Chuanhong Guo <gch981213@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        René van Dorst <opensource@...rst.com>
Subject: Re: Registering IRQ for MT7530 internal PHYs



On 12/30/2020 1:12 AM, Heiner Kallweit wrote:
> On 30.12.2020 10:07, DENG Qingfang wrote:
>> Hi Heiner,
>> Thanks for your reply.
>>
>> On Wed, Dec 30, 2020 at 3:39 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>>> I don't think that's the best option.
>>
>> I'm well aware of that.
>>
>>> You may want to add a PHY driver for your chip. Supposedly it
>>> supports at least PHY suspend/resume. You can use the RTL8366RB
>>> PHY driver as template.
>>
>> There's no MediaTek PHY driver yet. Do we really need a new one just
>> for the interrupts?
>>
> Not only for the interrupts. The genphy driver e.g. doesn't support
> PHY suspend/resume. And the PHY driver needs basically no code,
> just set the proper callbacks.

That statement about not supporting suspend/resume is not exactly true,
the generic "1g" PHY driver only implements suspend/resume through the
use of the standard BMCR power down bit, but not anything more
complicated than that.

Interrupt handling within the PHY itself is not defined by the existing
standard registers and will typically not reside in a standard register
space either, so just for that reason you do need a custom PHY driver.
There are other advantages if you need to expose additional PHY features
down the road like PHY counters, energy detection, automatic power down etc.

I don't believe we will see discrete/standalone Mediatek PHY chips, but
if that happens, then you would already have a framework for supporting
them.
-- 
Florian