linux-kernel - Re: [PATCH v3 05/12] PCI: of_property: Assign PCI instead of CPU bus address to dynamic bridge nodes

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Message-ID: <49aeb2b6-3635-4094-97bd-cbff506f017c@suse.de>
Date: Thu, 7 Nov 2024 13:51:34 +0200
From: Stanimir Varbanov <svarbanov@...e.de>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Bjorn Helgaas <helgaas@...nel.org>
Cc: Andrea della Porta <andrea.porta@...e.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczynski <kw@...ux.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Linus Walleij <linus.walleij@...aro.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Derek Kiernan <derek.kiernan@....com>,
 Dragan Cvetic <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Saravana Kannan <saravanak@...gle.com>, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-gpio@...r.kernel.org,
 Masahiro Yamada <masahiroy@...nel.org>, Stefan Wahren <wahrenst@....net>,
 Herve Codina <herve.codina@...tlin.com>,
 Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v3 05/12] PCI: of_property: Assign PCI instead of CPU bus
 address to dynamic bridge nodes

Hi Mani,

On 11/6/24 16:35, Manivannan Sadhasivam wrote:
> On Mon, Nov 04, 2024 at 05:49:37PM -0600, Bjorn Helgaas wrote:
>> On Mon, Nov 04, 2024 at 08:35:21PM +0530, Manivannan Sadhasivam wrote:
>>> On Mon, Nov 04, 2024 at 09:54:57AM +0100, Andrea della Porta wrote:
>>>> On 22:39 Sat 02 Nov     , Manivannan Sadhasivam wrote:
>>>>> On Mon, Oct 28, 2024 at 03:07:22PM +0100, Andrea della Porta wrote:
>>>>>> When populating "ranges" property for a PCI bridge, of_pci_prop_ranges()
>>>>>> incorrectly use the CPU bus address of the resource. Since this is a PCI-PCI
>>>>>> bridge, the window should instead be in PCI address space. Call
>>>>>> pci_bus_address() on the resource in order to obtain the PCI bus
>>>>>> address.
>>>>>
>>>>> of_pci_prop_ranges() could be called for PCI devices also (not just PCI
>>>>> bridges), right?
>>>>
>>>> Correct. Please note however that while the PCI-PCI bridge has the parent
>>>> address in CPU space, an endpoint device has it in PCI space: here we're
>>>> focusing on the bridge part. It probably used to work before since in many
>>>> cases the CPU and PCI address are the same, but it breaks down when they
>>>> differ.
>>>
>>> When you say 'focusing', you are specifically referring to the
>>> bridge part of this API I believe. But I don't see a check for the
>>> bridge in your change, which is what concerning me. Am I missing
>>> something?
>>
>> I think we want this change for all devices in the PCI address
>> domain, including PCI-PCI bridges and endpoints, don't we?  All those
>> "ranges" addresses should be in the PCI domain.
>>
> 
> Yeah, right. I was slightly confused by the commit message. Maybe including a
> sentence about how the change will work fine for endpoint devices would help.
> Also, why it went unnoticed till now (ie., both CPU and PCI addresses are same
> in many SoCs).

Most probably it is unnoticed because until now nobody has enabled
/selected CONFIG_PCI_DYNAMIC_OF_NODES ?

~Stan