[U-Boot] [PATCH] vexpress64: Juno: Change PCI buss addresses for IO to start from zero.

[Jeremy Linton]

|-----Original Message-----
|From: Sudeep Holla [mailto:sudeep.holla at arm.com]
|Sent: Tuesday, November 22, 2016 10:11 AM
|To: Tom Rini; Liviu Dudau
|Cc: Sudeep Holla; Lorenzo Pieralisi; Jeremy Linton; U-Boot ML
|Subject: Re: [U-Boot] [PATCH] vexpress64: Juno: Change PCI buss addresses
|for IO to start from zero.
|
|
|
|On 22/11/16 15:08, Tom Rini wrote:
|> On Tue, Nov 22, 2016 at 12:08:49PM +0000, Liviu Dudau wrote:
|>> On Tue, Nov 22, 2016 at 11:29:20AM +0000, Sudeep Holla wrote:
|>>> Hi Liviu,
|>>>
|>>> On Tue, Nov 22, 2016 at 11:19 AM, Liviu Dudau
|<Liviu.Dudau at foss.arm.com> wrote:
|>>>> Juno uses a 1:1 mapping between CPU and PCI addresses for IO.
|>>>> First, that will trip devices that cannot use more than 16 bits of
|>>>> addresses for IO, second it is un-necessary as the system can
|>>>> handle zero-based PCI addresses just fine.
|>>>>
|>>>> Change the mapping to start IO bus addresses from zero.
|>>>>
|>>>
|>>> I assume this require corresponding DT change, shout if that's not true.
|>>> If that's true, then does this patch not require patching of DT so
|>>> that systems not running Uboot with this patch continue to work and
|>>> we retain the mainline DT as is ?
|>>
|>> Yes, it does require DT changes, Jeremy Linton has a patch
|>
|> So to be clear, what level of coordination do we need between the two
|> parts being merged?  It would not be ideal to have combinations of
|> U-Boot and Linux not work.  Thanks!
|>
|
|What I had in mind is U-Boot modifying/fixing up the DT to adapt to this
|change so that we maintain compatibility and don't break anything. But I was
|not sure how feasible is that solution with other bootloaders like UEFI.

Hi,

UEFI already has the 0 based PIO in place, so in theory its broken with the current DT.

Put another way, I suspect that there are few (if any) juno's running out there, making use of PCIe PIO. Most of the boards people are likely to plug into the machine don't use PIO.

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