linux-kernel - Re: [PATCH v3 2/2] net: dsa: mt7530: Use GPIO polarity to generate correct reset sequence

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Message-ID: <20251204154557.b7asnuxq7hiy5zlq@skbuf>
Date: Thu, 4 Dec 2025 17:45:57 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Daniel Golle <daniel@...rotopia.org>
Cc: Frank Wunderlich <frankwu@....de>,
	Krzysztof Kozlowski <krzk@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Chen Minqiang <ptpt52@...il.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"Chester A. Unal" <chester.a.unal@...nc9.com>,
	DENG Qingfang <dqfext@...il.com>,
	Sean Wang <sean.wang@...iatek.com>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 2/2] net: dsa: mt7530: Use GPIO polarity to generate
 correct reset sequence

On Thu, Dec 04, 2025 at 01:50:52PM +0000, Daniel Golle wrote:
> On Thu, Dec 04, 2025 at 03:16:26PM +0200, Vladimir Oltean wrote:
> > If this is blocking progress for new device trees, can we just construct,
> > using of_machine_is_compatible(), a list of all boards where the device
> > tree defines incorrect reset polarity that shouldn't be trusted by the
> > driver when driving the reset GPIO? If we do this, we can also leave
> > those existing device trees alone.
> 
> From OpenWrt's point of view this would be kind of ugly as we would either
> have to extend the list of affected boards downstream, or fix the polarity
> in some but not all of our downstream DTS files.

Including the downstream-only boards, how many compatibles are we
talking about? If we patched mainline to cover all, are you confident
that it would be an exhaustive solution?

> I'd prefer to rather have the option to force the "wrong" GPIO
> polarity for theoretical future boards with that (very unlikely to
> ever exist) NOT gate between the SoC GPIO and switch reset line. That
> would allow to gradually update boards to reflect the physical reality
> and yet the driver would not break if the GPIO polarity is stated
> wrongly.

I didn't get that from this thread - how would you prefer having this
option implemented exactly?