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

[Marek Vasut <marex@denx.de>]

On Wednesday, December 04, 2013 at 06:49:55 AM, Richard Zhu wrote:
> Hi Marek:
> 
> Best Regards
> Richard Zhu
> 
> > -----Original Message-----
> > From: Marek Vasut [mailto:marex@denx.de]
> > Sent: Friday, November 29, 2013 1:56 AM
> > To: Jingoo Han
> > Cc: 'Tim Harvey'; 'Pratyush Anand'; linux-arm-kernel@lists.infradead.org;
> > linux-pci@vger.kernel.org; 'Bjorn Helgaas'; 'Frank Li'; 'Harro Haan';
> > 'Mohit KUMAR DCG'; Zhu Richard-R65037; 'Sascha Hauer'; 'Sean Cross';
> > 'Shawn Guo'; 'Siva Reddy Kallam'; 'Srikanth T Shivanand'; 'Troy Kisky';
> > 'Yinghai Lu' Subject: Re: [PATCH 2/7] [RFC] PCI: imx6: remove outbound
> > io/mem ATU region mapping
> > 
> > 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?
> 
> [Richard] One Pericom PI7C9X2G303EL pcie switch, and two pcie ep
> deivces(one is intel e1000e nic, the other is one xhci device) are tested
> on imx6q sabresd board. Without removing outbound io/mem regions view map
> during the cfg0/1 read/write cycle, both of these devices can't work well
> at my side. Works well after remove them during the cfg0/1 read/write
> cycles.
> Same to Tim's situation about switch implementation.

Thanks Richard! I am just wondering what kind of conclusion can we draw from 
this. Let me reiterate what we have:

- i.MX6 has 4 inbound and 4 outbound iATU regions, is that correct, Richard?
- If we program the iATU regions, the i.MX6 PCIe doesn't work with switch.

Is there some special sause to the iATU on MX6 maybe ?