Re: [PATCH v2 1/4] dt-bindings: imx6q-pcie: Add reg-name "dbi2" and "atu" for i.MX8M PCIe Endpoint

[Conor Dooley <conor@kernel.org>]

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On Wed, Jul 24, 2024 at 08:32:34AM +0200, Krzysztof Kozlowski wrote:
> On 24/07/2024 08:26, Hongxing Zhu wrote:
> >> -----Original Message-----
> >> From: Krzysztof Kozlowski <krzk@kernel.org>
> >> Sent: 2024年7月24日 14:07
> >> To: Hongxing Zhu <hongxing.zhu@nxp.com>; robh@kernel.org;
> >> krzk+dt@kernel.org; conor+dt@kernel.org; shawnguo@kernel.org;
> >> l.stach@pengutronix.de
> >> Cc: devicetree@vger.kernel.org; linux-pci@vger.kernel.org;
> >> linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org;
> >> kernel@pengutronix.de; imx@lists.linux.dev
> >> Subject: Re: [PATCH v2 1/4] dt-bindings: imx6q-pcie: Add reg-name "dbi2" and
> >> "atu" for i.MX8M PCIe Endpoint
> >>
> >> On 24/07/2024 05:03, Richard Zhu wrote:
> >>> Add reg-name: "dbi2", "atu" for i.MX8M PCIe Endpoint.
> >>
> >> This we see in the diff. What I do not see is why? Hardware changed? How come?
> >>
> > For i.MX8M PCIe EP, the dbi2 and atu address are pre-defined in the driver.
> > This method is not good.
> > In commit b7d67c6130ee ("PCI: imx6: Add iMX95 Endpoint (EP) support"),
> > Frank suggests to fetch the dbi2 and atu from DT directly.
> > This series is preparation to do that for i.MX8M PCIe EP.
> 
> This all must be explained in commit msg.
> 
> Anyway, this will be an ABI break, so explain exactly why it is OK to
> break the ABI.

And the driver needs to be written in such a way that if only two reg
properties are provided, it falls back to the old method of acquiring
the two new reg regions. I didn't see a driver patch on v1, so I missed
that this is what was actually the plan - I thought that this was just
adding two missing regions.

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