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

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Date:	Sun, 22 Sep 2013 16:46:34 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Pratyush Anand <pratyush.anand@...com>,
	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 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);
>>         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 :-(

Thanks
Kishon
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