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

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Message-ID: <20251130082218.mvxlk3p2pxdny2ij@skbuf>
Date: Sun, 30 Nov 2025 10:22:18 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Chen Minqiang <ptpt52@...il.com>
Cc: 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>,
	Daniel Golle <daniel@...rotopia.org>,
	DENG Qingfang <dqfext@...il.com>,
	Sean Wang <sean.wang@...iatek.com>, Andrew Lunn <andrew@...n.ch>,
	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 Sun, Nov 30, 2025 at 07:46:03AM +0800, Chen Minqiang wrote:
> This change makes the driver fully backward-compatible with older,
> incorrect DTS files that marked the reset line as GPIO_ACTIVE_HIGH

The driver _is_ already backward-compatible with incorrect device trees.
This patch makes it compatible with "correct" device trees.

We need care taken in one more area: when you make updates to the device
tree, *old* versions of the kernel are not compatible with the latest
device tree, which is not OK.

So ideally:
- patch 2/2 should be considered a bug fix and backported to stable kernels
- you wait for some time to pass between when patch 2/2 is merged, and
  when patch 1/2 is merged, so that users who get an updated device tree
  have gotten the kernel compatibility patch through stable channels

Then you need to consider that you break "git bisect" if you keep the
device tree the same (i.e. the latest) and just change kernels. That is
a trade-off that needs to be well justified (cost/benefit).