linux-kernel - Re: [PATCH V3] pci: exynos: split into two parts such as Synopsys part and Exynos part

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Date:	Mon, 23 Sep 2013 09:44:28 +0530
From:	Pratyush Anand <pratyush.anand@...com>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	Arnd Bergmann <arnd@...db.de>, Jingoo Han <jg1.han@...sung.com>,
	'Bjorn Helgaas' <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	'Kukjin Kim' <kgene.kim@...sung.com>,
	Mohit KUMAR DCG <Mohit.KUMAR@...com>,
	'Sean Cross' <xobs@...agi.com>,
	'Thierry Reding' <thierry.reding@...il.com>,
	'SRIKANTH TUMKUR SHIVANAND' <ts.srikanth@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH V3] pci: exynos: split into two parts such as Synopsys
 part and Exynos part

Hi Kishon,


On Sun, Sep 22, 2013 at 07:16:34PM +0800, Kishon Vijay Abraham I wrote:
> Hi Arnd,
> 
> Thanks for replying :-)
> 
> On Sunday 22 September 2013 03:33 AM, Arnd Bergmann wrote:
> > On Saturday 21 September 2013, Kishon Vijay Abraham I wrote:
> >> {
> >>         u32 val;
> >>         void __iomem *val1;
> >>         void __iomem *dbi_base = pp->dbi_base;
> >>
> >>         /* Program viewport 0 : INBOUND : MEMORY*/
> >>         val = PCIE_ATU_REGION_INBOUND | (0 & 0xF);
> >>         dw_pcie_writel_rc(pp, val, dbi_base + PCIE_ATU_VIEWPORT);
> >>         val1 = ioremap(0x80000000, 0x5fffffff);
> > 
> > The ioremap here makes no sense at all, and I suspect it will fail anyway,
> > because you exhaust the vmalloc area size, but since the value is not
> > used anywhere, it won't matter.
> > 
> >>         dw_pcie_writel_rc(pp, 0x80000000, dbi_base + PCIE_ATU_LOWER_BASE);
> >>         dw_pcie_writel_rc(pp, 0, dbi_base + PCIE_ATU_UPPER_BASE);
> >>         /* in_mem_size must be in power of 2 */
> >>         dw_pcie_writel_rc(pp, 0x5FFFFFFF, dbi_base + PCIE_ATU_LIMIT);

This is wrong. You should program here 0xBFFFFFFF.

Translation rule is as follows:

Region between "Start Address" and "End Address" is translated to
"Target Address" with region size = "End Address" - "Start Address".
Where: Start Address = (PCIE_ATU_UPPER_BASE | PCIE_ATU_LOWER_BASE)
        End Address = (PCIE_ATU_UPPER_BASE | PCIE_ATU_LIMIT)
        Target Address = (PCIE_ATU_UPPER_TARGET | PCIE_ATU_LOWER_TARGET) 

> >>         dw_pcie_writel_rc(pp, 0x80000000, dbi_base + PCIE_ATU_LOWER_TARGET);
> >>         dw_pcie_writel_rc(pp, 0, dbi_base + PCIE_ATU_UPPER_TARGET);
> > 
> > These numbers need to come from somewhere, you shouldn't just hardcode them, 
> 
> right. I'm still in the process of getting it work ;-)
> > 
> > I guess you should either program an inbound window covering the entire 64-bit
> > address space, or you should look at the top-level "memory" nodes to find
> > the location of physical RAM.
> > 
> > I can't see anything wrong with the way it's set up though, unless you have
> > an IOMMU. Can you confirm that there is no IOMMU (aka SMMU) in your system
> > that handles the PCIe root complex?
> 
> There is a MMU for PCIe root complex but that's disabled.
> > 
> >> I somehow starting to doubt the DMA address programmed in the ethernet card
> >> which is in my RAM address range (0x80000000 to 0xBFFFFFFF). Should this
> >> address be programmed in the BAR of the ethernet card? How should it be done?
> > 
> > No, it should not be in the BAR. The ethernet device driver calls dma_map_*
> > or pci_map_* interfaces to get a valid token that can be passed into the
> > device registers that are starting the DMA. You have to ensure that the
> > dma_map_ops for the device return the value that is set up in the translation.
> > 
> > The normal case is an identity mapping between device DMA space and host
> > memory space, i.e. PCIE_ATU_LOWER_TARGET == PCIE_ATU_LOWER_BASE, so
> > in the dma_map_single implementation, phys_addr_t == dma_addr_t.
> > 
> > If you set up the dma_addr_t space to start at 0 instead, you have to add
> > the offset in the dma_map_ops.
> 
> My DMA address is in 0x80000000 to 0xBFFFFFFF range and I program my inbound
> translation for this range. Not sure what is missing still :-(

Hope, above modification helps. Let me know.

Regards
Pratyush
> 
> Thanks
> Kishon
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