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

[Marek Vasut <marex@denx.de>]

Dear 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@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?

Richard is on the CC. Richard, can you please confirm those?

Thanks!

> 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.

Best regards,
Marek Vasut