Re: [PATCH v3 5/6] dt-bindings: net: dsa: make reset optional and add rgmii-mode to mt7531

From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Peter Geis <pgwipeout@gmail.com>,
	Frank Wunderlich <frank-w@public-files.de>
Cc: "Heiko Stuebner" <heiko@sntech.de>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"Frank Wunderlich" <linux@fw-web.de>,
	linux-mediatek@lists.infradead.org,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Vivien Didelot" <vivien.didelot@gmail.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Vladimir Oltean" <olteanv@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Sean Wang" <sean.wang@mediatek.com>,
	"Landen Chao" <Landen.Chao@mediatek.com>,
	"DENG Qingfang" <dqfext@gmail.com>,
	"Linux Kernel Network Developers" <netdev@vger.kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	arm-mail-list <linux-arm-kernel@lists.infradead.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Greg Ungerer" <gerg@kernel.org>,
	"René van Dorst" <opensource@vdorst.com>,
	"Mauro Carvalho Chehab" <mchehab+samsung@kernel.org>
Subject: Re: [PATCH v3 5/6] dt-bindings: net: dsa: make reset optional and add rgmii-mode to mt7531
Date: Mon, 9 May 2022 08:48:52 +0200	[thread overview]
Message-ID: <41d6b00f-d8ac-ca54-99db-ea99c9049e0a@linaro.org> (raw)
In-Reply-To: <CAMdYzYrG8bK-Yo15RjhhCQKS4ZQW53ePu1q4gbGxVVNKPJHBWg@mail.gmail.com>

On 08/05/2022 19:04, Peter Geis wrote:
> On Sun, May 8, 2022 at 8:12 AM Frank Wunderlich <frank-w@public-files.de> wrote:
>>>
>>> I think the issue is more for the description itself.
>>>
>>> Devicetree is only meant to describe the hardware and does in general don't
>>> care how any firmware (Linux-kernel, *BSD, etc) handles it. So going with
>>> "the kernel does it this way" is not a valid reason for a binding change ;-) .

Exactly. The argument in commit msg was not matching the change, because
driver implementation should not be (mostly) a reason for such changes.

>>>
>>> Instead in general want to reason that there are boards without this reset
>>> facility and thus make it optional for those.
>>
>> if only the wording is the problem i try to rephrase it from hardware PoV.
>>
>> maybe something like this?
>>
>> https://github.com/frank-w/BPI-R2-4.14/commits/5.18-mt7531-mainline2/Documentation/devicetree/bindings/net/dsa/mediatek%2Cmt7530.yaml

Looks ok.

>>
>> Another way is maybe increasing the delay after the reset (to give more time all
>> come up again), but imho it is no good idea resetting the gmac/mdio-bus from the
>> child device.
>>
>> have not looked into the gmac driver if this always  does the initial reset to
>> have a "clean state". In this initial reset the switch will be resetted too
>> and does not need an additional one which needs the gmac/mdio initialization
>> to be done again.
> 
> For clarification, the reset gpio line is purely to reset the phy.
> If having the switch driver own the reset gpio instead of the gmac
> breaks initialization that means there's a bug in the gmac driver
> handling phy init.
> In testing I've seen issues moving the reset line to the mdio node
> with other phys and the stmmac gmac driver, so I do believe this is
> the case.

Yes, this seems reasonable, although Frank mentioned that reset is
shared with gmac, so it resets some part of it as well?

Best regards,
Krzysztof

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