Re: [PATCH V5 00/15] MMCONFIG refactoring and support for ARM64 PCI hostbridge init based on ACPI

[Tomasz Nowicki <tn@semihalf.com>]

On 04.03.2016 11:55, Lorenzo Pieralisi wrote:
> On Thu, Mar 03, 2016 at 09:24:56AM -0500, Sinan Kaya wrote:
>> >On 3/3/2016 6:23 AM, Lorenzo Pieralisi wrote:
>>> > >x86 and IA64 claim PCI resources on boot and live with that (well, minus
>>> > >the gazillions x86 pci= parameters that change the PCI resources assignment
>>> > >one way or another), comments very welcome in particular on the pci=realloc
>>> > >option and its usage.
>> >
>> >I have been working with Linux PCIe over 3 years. I never used
>> >pci=realloc argument.
>> >
>> >The v5 series minus [PATCH V5 11/15] drivers: pci: add generic code to
>> >claim bus resources is working just fine and is ready to go upstream
>> >in my opinion. It passed my internal testing with different types of
>> >endpoints.
>> >
>> >The inclusion of this patch is now requiring everybody to add
>> >pci=realloc argument otherwise the resources assigned by the UEFI BIOS
>> >are not working.
>> >
>> >I think there is still some work to be done in this patch and is too
>> >early to be included into the series. It is blocking progress of the
>> >series which is sitting on review over 1 year already.
> First off, I think that's specious, patch 11 is not blocking anything,
> if you and Tomasz want to drop it go ahead and take responsibility
> of the consequences.
>
> I am not saying patch 11 is perfect, it is there to review, if you
> spot bugs point them out.
>
> If you are interested and willing to make an effort to understand why I
> asked Tomasz to integrate it, a bit of background here:
>
> http://permalink.gmane.org/gmane.linux.kernel.pci/44830
>
> If we want to drop patch 11, we are going to discard whatever FW
> set-up at FW/OS hand-off and reassign everything. Want to do it ?
> Go ahead.
>
> I wrote it in my previous email, probably it was not clear, so, here we
> go again.
>
> If we want to at least consider the FW PCI configuration at FW/OS
> handoff, we should read the PCI bridge apertures and claim them, when
> that fails reassign the corresponding PCI bus hierarchy (which means
> releasing the bridge resources and downstream devices and reassign
> them), that's what pci=realloc does.
>
> I think that it is a command line option since it has to be a choice,
> ie overriding FW set-up should be an option, not a default.
>
> Patch 11 does what x86 does in arch code arch/x86/pci/i386.c,
>
> pcibios_resource_survey()
>
> and that works for them (of course, minus quirks that do exist).
>
> I could integrate the code implementing pci=realloc in patch 11 so
> that we realloc by default all resources claimed that failed (which
> means that bridges are resized accordingly and you won't be forced
> to use pci=realloc on command line).
>

I agree with Lorenzo. Just because v3 works it does not mean we want to 
go this way. Also, I think we should realloc all resources claimed that 
failed, w/o need to use pci=realloc on command line.

Tomasz