linux-kernel - Re: [PATCH 6/6] ARM: dts: Add pcie controller node for Samsung EXYNOS5440 SoC

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Date:	Fri, 07 Jun 2013 18:19:40 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Jason Gunthorpe' <jgunthorpe@...idianresearch.com>
Cc:	'Kukjin Kim' <kgene.kim@...sung.com>,
	'Bjorn Helgaas' <bhelgaas@...gle.com>,
	linux-samsung-soc@...r.kernel.org, linux-pci@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	'Grant Likely' <grant.likely@...retlab.ca>,
	'Andrew Murray' <andrew.murray@....com>,
	'Thomas Petazzoni' <thomas.petazzoni@...e-electrons.com>,
	'Thierry Reding' <thierry.reding@...onic-design.de>,
	'Surendranath Gurivireddy Balla' <suren.reddy@...sung.com>,
	'Siva Reddy Kallam' <siva.kallam@...sung.com>,
	'Thomas Abraham' <thomas.abraham@...aro.org>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH 6/6] ARM: dts: Add pcie controller node for Samsung
 EXYNOS5440 SoC

On Tuesday, April 09, 2013 1:56 AM, Jason Gunthorpe wrote:
> On Mon, Apr 08, 2013 at 06:08:53PM +0900, Jingoo Han wrote:
> 
> > I have a question.  Now, I am reviewing the Tegra PCIe, Marvell PCIe
> > patchset.  However, in the case of Exynos PCIe, 'downstream I/O' and
> > 'non-prefetchable memory' are different between PCIe0 and PCIe1.
> > These regions are not shared.
> >
> > PCIe0:
> > 	ranges = <0x00000800 0 0x40000000 0x40000000 0 0x00200000   /* configuration space */
> > 		  0x81000000 0 0	  0x40200000 0 0x00004000   /* downstream I/O */
> > 		  0x82000000 0 0	  0x40204000 0 0x10000000>; /* non-prefetchable memory */
> >
> > PCIe1:
> > 	ranges = <0x00000800 0 0x40000000 0x40000000 0 0x00200000   /* configuration space */
> > 		  0x81000000 0 0	  0x40200000 0 0x00004000   /* downstream I/O */
> > 		  0x82000000 0 0	  0x40204000 0 0x10000000>; /* non-prefetchable memory */
> >
> > PCIe0 uses 0x40000000~0x5fffffff, PCI1 uses 0x60000000~0x7fffffff.
> >
> > How can I handle this? :)
> 
> You need to dig into where this range restriction comes from, and how
> it interacts with the PCI-E root bridge's window registers. Is there
> another set of registers that control this? Is it hardwired into the
> silicon? Do the root port window registers control this?
> 
> I'm looking at functions like exynos_pcie_prog_viewport_mem_outbound
> and wondering if the driver already controls this window.. But it
> looks like there may be some restrictions.
> 
> Marvell also has unshared regions, but the driver arranges for those
> ranges to be setup dynamically based on writes to the bridge's window
> registers from the Linux PCI core, so the region is always in sync
> with what the Linux PCI core is trying to do.
> 
> The desired perfect outcome is to have a single logical 'shared'
> region for memory and I/O - give that region to the PCI core via
> struct resources, then the PCI core tells the driver and HW what
> portion of that region belongs to each root port via a write to the
> root port bridge's window registers. The net result is still
> non-overlapping regions, but the allocation of space between port 0
> and port 1 is performed at run time.
> 
> I don't really know enough about your hardware to give you better
> advice, sorry. The general guidance to try and follow the PCI-E spec
> for a root complex is good, but if the HW can't do it, or it would
> make the driver too complex, then one PCI domain per port will always
> work (this is similar to your original driver, but with domains).
> 
> The main advantage to following the PCI-E specs and allowing for
> dynamic allocation of address space is that it lets you reserve less
> address space for PCI-E, and this in turn gives you more low mem
> address space to use for DRAM.

Hi Jason Gunthorpe,

I implemented 'Single domain' with Exynos PCIe for last two months;
however, it cannot work properly due to the hardware restriction.
Each MEM region is hard-wired.

Thus, I will send Exynos PCIe V3 patch as 'Separate domains'.

Best regards,
Jingoo Han

> 
> > The following is right?
> 
> > +       pcie-controller {
> > 		.....
> > +               ranges = <0x82000000 0 0x40000000 0x40000000 0 0x00200000   /* port 0 registers */
> > +                         0x82000000 0 0x60000000 0x60000000 0 0x00200000   /* port 1 registers */
> > +                         0x81000000 0 0          0x40200000 0 0x00004000   /* port 0 downstream I/O */
> > +                         0x81000000 0 0          0x60200000 0 0x00004000   /* port 1 downstream I/O */
> > +                         0x82000000 0 0x40204000 0x40204000 0 0x10000000>; /* port 0 non-prefetchable
> memory */
> > +                         0x82000000 0 0x40204000 0x60204000 0 0x10000000>; /* port 1 non-prefetchable
> memory */
> 
> 
> > +
> > +               pci@1,0 {
> > +                       device_type = "pci";
> > +                       assigned-addresses = <0x82000800 0 0x40000000 0 0x00200000
> > +                                                 0x81000800 0 0x40200000 0 0x00004000
> > +                                                 0x81000800 0 0x40204000 0 0x10000000>;
> 
> Would be:
> 
>                        ranges = <0x81000800 0 0x40200000  0x81000800 0 0x40200000  0 0x00004000
>                                  0x81000800 0 0x40204000  0x81000800 0 0x40204000  0 0x10000000>;
>                        assigned-addresses = <0x82000800 0 0x40000000  0 0x00200000>;
> 
> Jason

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