linux-kernel - Re: [PATCH v8 2/7] PCI: dwc: Use devicetree 'ranges' property to get rid of cpu_addr

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Message-ID: <Z5elHSnnFaDDD8Cc@ryzen>
Date: Mon, 27 Jan 2025 16:24:13 +0100
From: Niklas Cassel <cassel@...nel.org>
To: Frank Li <Frank.li@....com>
Cc: Bjorn Helgaas <helgaas@...nel.org>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev
Subject: Re: [PATCH v8 2/7] PCI: dwc: Use devicetree 'ranges' property to get
 rid of cpu_addr_fixup() callback

On Thu, Jan 23, 2025 at 02:15:10PM -0500, Frank Li wrote:
> On Thu, Jan 23, 2025 at 01:04:22PM -0600, Bjorn Helgaas wrote:
> > On Thu, Jan 23, 2025 at 10:21:36AM -0500, Frank Li wrote:
> > > On Fri, Jan 17, 2025 at 10:42:37AM -0500, Frank Li wrote:
> > > > On Thu, Jan 16, 2025 at 05:29:16PM -0600, Bjorn Helgaas wrote:
> > > > > On Thu, Jan 16, 2025 at 05:14:00PM -0600, Bjorn Helgaas wrote:
> > > > > > On Tue, Nov 19, 2024 at 02:44:20PM -0500, Frank Li wrote:
> > > > > > > parent_bus_addr in struct of_range can indicate address information just
> > > > > > > ahead of PCIe controller. Most system's bus fabric use 1:1 map between
> > > > > > > input and output address. but some hardware like i.MX8QXP doesn't use 1:1
> > > > > > > map.
> > > ...
> >
> > > 	I saw you have not picked all of these patches during you rework
> > > pci git branches.
> > >
> > > 	I know you are busy, do you have chance to pick left patch for 6.14.
> >
> > This series had a mix of things: several patches related to
> > .cpu_addr_fixup(), plus several unrelated ones for PHY mode and i.MX8Q
> > support.  I think I picked up all the unrelated ones.
> >
> > .cpu_addr_fixup() is a generic problem that affects dwc (dra7xx, imx6,
> > artpec6, intel-gw, visconti), cadence (cadence-plat), and now
> > apparently microchip.
> >
> > I deferred these because I'm hoping we can come up with a more generic
> > solution that's easier to apply across all these cases.  I don't
> > really want to merge something that immediately needs to be reworked
> > for other drivers.
> >
> > A few of the things I wonder about:
> >
> >   - dw_pcie_get_parent_addr() has no DWC dependencies, so it doesn't
> >     make sense to me to have it be DWC-specific and copy and pasted
> >     to other places that need something similar.
> >
> >   - It doesn't seem elegant to iterate through for_each_pci_range() in
> >     devm_of_pci_get_host_bridge_resources(), then again in
> >     dw_pcie_host_init() for io_bus_addr, then again in
> >     dw_pcie_iatu_setup() for each window.  Maybe that's the best we
> >     can do, but maybe there's a way to capture what we need on the
> >     first time through.
> >
> >   - The connection between .cpu_addr_fixup() and use_parent_dt_ranges
> >     is clear in the patches remove a .cpu_addr_fixup(), but not in the
> >     DWC patches on the other end.
> >
> >   - Ideally, "use_parent_dt_ranges" would be the default and we
> >     wouldn't have a flag to indicate that, and drivers would have to
> >     opt out instead of opt in.  They basically already do that by
> >     implementing .cpu_addr_fixup(), so maybe we can take advantage of
> >     that fact.
> 
> Okay, thanks. let me think how to improve it after 6.14.


Small nit that I saw when looking at this series.

Some patches use "Internal Address (IA)", but other patches use
"Intermediate Address (IA)". For the re-spin, use one term consistently.


Kind regards,
Niklas