[PATCH 2/7] [RFC] PCI: imx6: remove outbound io/mem ATU region mapping

[Jingoo Han]

On Wednesday, November 27, 2013 5:44 PM, Marek Vasut wrote:
> Wednesday, November 27, 2013 1:30 PM, Pratyush Anand wrote:
> > On Wed, Nov 27, 2013 at 05:10:43AM +0800, Marek Vasut wrote:
> > > From: Tim Harvey <tharvey at gateworks.com>
> > >
> > > The IMX6 iATU is used for address translation between the AXI bus
> > > address space and PCI address space.  This is used for type0 and type1
> > > config cycles but is not necessary for outbound io/mem regions.
> > >
> > > This patch removes the calls that inappropriately re-configures the ATU
> > > viewport for outbound memory and IO after config cycles and removes them
> > > altogether as they are not necessary.
> >
> > Yes, they are not necessary for all the cases where translation is one
> > to one. So so for sure all the platform till now introduced should
> > work.
> > But, what about a platform where memory translation is not one to one?
> >
> > Existing code should work with all sort of memory translation on a
> > platform having atleast two viewports capable of programming any type
> > of outbound transaction.
> 
> Full ACK, that's why it's called RFC.
> 
> > > This resolves issues with PCI devices behind switches and has been tested
> > > with a Gige device behind a PLX PEX860x switch.  More testing is needed
> > > for other configurations.
> >
> > I do not understand if MX6 has 4 Outbound Viewport then how this patch
> > helps?
> > -- PCI devices behind switches would not have been working because
> > CFG1 transaction would not have been correct.
> > -- It works with this patch. This patch changes viewport for CFG1 from
> > 1 to 0.
> > -- Can it be possible that MX6 has some restriction on viewport
> > programming capability. I mean,like only viewport0 can be programmed
> > for CFG0/1?
> 
> Tim ?
> 
> Here is the MX6 datasheet [1], the section 48.3.9.1.1 and 48.3.9.1.2 describe
> the iATU configuration on MX6. My understanding from this description is that
> the MX6 has 4 inbound and 4 outbound iATU regions. Am I wrong ?

The numbers of inbound and outbound are hardware-configurable features.
Thus, these numbers  can be confirmed by Freescale  hardware engineers.
How about asking Freescale hardware engineers, if possible?

Best regards,
Jingoo Han
> 
> [1] http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf
> 
> > Otherwise I do not find any convincing reason that why this patch
> > helps in resolving issues with PCI devices behind switches.