linux-kernel - Re: [PATCH v9 0/7] PCI: dwc: opitimaze RC Host/EP pci_fixup

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Message-ID: <Z5pJF9MGENNDqq/O@lizhi-Precision-Tower-5810>
Date: Wed, 29 Jan 2025 10:28:23 -0500
From: Frank Li <Frank.li@....com>
To: Niklas Cassel <cassel@...nel.org>
Cc: 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 v9 0/7] PCI: dwc: opitimaze RC Host/EP pci_fixup_addr()

On Wed, Jan 29, 2025 at 11:13:42AM +0100, Niklas Cassel wrote:
> Hello Frank,
>
> Typo in subject:
> s/opitimaze/optimize/
>
>
> On Tue, Jan 28, 2025 at 05:07:33PM -0500, Frank Li wrote:
> >
> > Bjorn's comments in https://lore.kernel.org/imx/20250123190900.GA650360@bhelgaas/
> >
> > > After all cpu_address_fixup() removed, we can remove use_parent_dt_ranges
> > > in one clean up patches.
> > >
> > >
> >   ...
> > >  dw_pcie_rd_other_conf
> > >  dw_pcie_wr_other_conf
> > >    dw_pcie_prog_outbound_atu() only called if pp->cfg0_io_shared,
> > >    after an ECAM map via dw_pcie_other_conf_map_bus() and subsequent
> > >    successful access; atu.cpu_addr came from pp->io_base, set by
> > >    dw_pcie_host_init() from pci_pio_to_address(), which I'm pretty
> > >    sure returns a CPU address.
> >
> > io_base is parent_bus_address
> >
> > >    So this still looks wrong to me.  In addition, I think doing the
> > >    ATU setup in *_map() and restore in *rd/wr_other_conf() is ugly
> > >    and looks unreliable.
> >
> > ....
> >
> > >  dw_pcie_pme_turn_off
> > >    atu.cpu_addr came from pp.msg_res, set by
> > >    dw_pcie_host_request_msg_tlp_res() to a CPU address at the end of
> > >    the first MMIO bridge window.  This one also looks wrong to me.
> >
> > Fixed at this version.
>
>
> I feel like it would have been easier if you replied to Bjorn's comments
> directly in the thread instead of pasting them here (to a cover letter).
>
>
> Please don't shoot the messenger, but I don't see any reply to (what I
> assume is the biggest reason why Bjorn did not merge this series):
>
> ""
> .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.
> ""
>
> It should probably state in the cover letter how v9 addresses Bjorn's
> concern when it comes to other PCI controller drivers, especially those
> that are not DWC based.

Thank you for your reminder, I forget mentions this in cover letter. I
create new patch to figure out this Bjorn's problem.

PCI: Add parent_bus_offset to resource_entry

With above patch, other platform will be easy apply the same method.

Frank
>
>
> Kind regards,
> Niklas