[U-Boot] Ethernet i210 (e1000 driver) on tegra K1

[Stephen Warren <swarren@wwwdotorg.org>]

On 10/30/2015 05:07 AM, Ivan Mercier wrote:
> Hi,
>
> I'm using a ethernet controller intel i210
> (http://www.commell.com.tw/product/Surveillance/MPX-210.htm) on my
> nvidia tegra k1 jetson.

(You didn't actually CC anyone involved with Tegra, so I only 
accidentally noticed this while I was looking at my mailing list folder)

> I not an expert with pci, but the only way to make it working in u-boot
> (upstream) is with the workaround below.
>
> E1000 is very common, so finding a critical bug in this driver seems
> weird...
> Do you think there is a bug in e1000.c or in tegra pci layer?

> diff --git a/drivers/net/e1000.c b/drivers/net/e1000.c

> @@ -5186,7 +5186,7 @@ static int _e1000_transmit(struct e1000_hw *hw,
> void *txpacket, int length)
>       txp = tx_base + tx_tail;
>       tx_tail = (tx_tail + 1) % 8;
>
> -    txp->buffer_addr = cpu_to_le64(virt_to_bus(hw->pdev, nv_packet));
> +    txp->buffer_addr = cpu_to_le64((unsigned long) nv_packet);
>       txp->lower.data = cpu_to_le32(hw->txd_cmd | length);
>       txp->upper.data = 0;

In order to work out what's going on, perhaps you could print out the 
values of nv_packet and virt_to_bus(hw->pdev, nv_packet).

It's not terribly surprising that removing the call to virt_to_bus 
works, since IIRC U-Boot on Tegra uses the same address setup for the 
PCIe bus as for CPU physical addresses as for CPU virtual addresses.

So, the question is: what is virt_to_bus() doing, and is it the right 
API to call?

I see that virt_to_bus() is defined as:

e1000.c:

#define virt_to_bus(devno, v)   pci_virt_to_mem(devno, (void *) (v))

pci.h:

#define pci_virt_to_mem(dev, addr) \
         pci_virt_to_bus((dev), (addr), PCI_REGION_MEM)

#define pci_virt_to_bus(dev, addr, flags) \
         pci_hose_phys_to_bus(pci_bus_to_hose(PCI_BUS(dev)), \
                              (virt_to_phys(addr)), (flags))

I know that the RTL8169 driver works on the same board (it's soldered 
down and attached to the other PCIe root port on the SoC). For what 
looks like the same "use case", it seems to call pci_mem_to_phys() which is:

pci.h:

#define pci_mem_to_phys(dev, addr) \
         pci_bus_to_phys((dev), (addr), PCI_REGION_MEM)

#define pci_bus_to_phys(dev, addr, flags) \
         pci_hose_bus_to_phys(pci_bus_to_hose(PCI_BUS(dev)), (addr), \
				(flags))

That's odd, since one of those does a phys -> bus translation and the 
other does a bus -> phys translation. That's the opposite direction, so 
both can't possibly be right. I wonder if those mapping functions are 
no-ops on whatever architectures the e1000 driver has been used on (and 
hence have caused no issues), but fail for some reason on ARM?

(The other difference is the call to virt_to_phys(), but that's a no-op 
on ARM as far as I can tell).