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Date: Mon, 17 Mar 2025 14:45:39 -0500
From: Bjorn Helgaas <helgaas@kernel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Frank Li <Frank.Li@nxp.com>, Tony Lindgren <tony@atomide.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Siddharth Vadapalli <s-vadapalli@ti.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
	Bjorn Helgaas <bhelgaas@google.com>, linux-omap@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC NOT TESTED 0/2] PCI: dra7xx: Try to clean up
 dra7xx_pcie_cpu_addr_fixup()
Message-ID: <20250317194539.GA969005@bhelgaas>
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In-Reply-To: <20250317184427.7wkcr7jwu53r5jog@thinkpad>

On Tue, Mar 18, 2025 at 12:14:27AM +0530, Manivannan Sadhasivam wrote:
> On Mon, Mar 17, 2025 at 12:30:08PM -0500, Bjorn Helgaas wrote:
> > On Thu, Mar 13, 2025 at 11:35:21AM +0530, Manivannan Sadhasivam wrote:
> > > On Wed, Mar 05, 2025 at 11:20:21AM -0500, Frank Li wrote:
> > > > This patches basic on
> > > > https://lore.kernel.org/imx/20250128-pci_fixup_addr-v9-0-3c4bb506f665@nxp.com/
> > > > 
> > > > I have not hardware to test.
> > > > 
> > > > Look for driver owner, who help test this and start move
> > > > forward to remove cpu_addr_fixup() work.
> > > 
> > > If you remove cpu_addr_fixup() callback, it will break backwards
> > > compatibility with old DTs.
> > 
> > Do you have any pointers to DTs that will be broken?  Or to
> > commits where they were fixed?
> 
> Any patch that fixes issues in DT and then makes the required
> changes in the driver without accounting for the old DTs will break
> backwards compatibility.

Right, I guess the rule is that if we have patches that fix DT issues,
we should apply them as soon as possible.

And later if we ever have confidence that unfixed DTs no longer exist
(or if we can identify and work around them in the kernel), we can
remove the .cpu_addr_fixup().

Bjorn