[dpdk-dev] [PATCH] eal: map io resources for non x86 architectures

[Santosh Shukla]

On Thu, Dec 17, 2015 at 3:31 PM, Santosh Shukla <sshukla at mvista.com> wrote:
> On Thu, Dec 17, 2015 at 3:08 PM, Yuanhan Liu
> <yuanhan.liu at linux.intel.com> wrote:
>> On Wed, Dec 16, 2015 at 07:21:55PM +0530, Santosh Shukla wrote:
>>> On Wed, Dec 16, 2015 at 6:18 PM, Yuanhan Liu
>>> <yuanhan.liu at linux.intel.com> wrote:
>>> > On Wed, Dec 16, 2015 at 01:31:04PM +0100, David Marchand wrote:
>>> >> x86 requires a special set of instructions to access ioports, but other
>>> >> architectures let you remap io resources.
>>> >> So let eal remap io resources by accepting IORESOURCE_IO flag for
>>> >> architectures other than x86.
>>> >
>>> > One question: this patch could be a replacement of the igbuio_iomap patch
>>> > from Santosh? If so, I like it: It's more elegant.
>>> >
>>> >         --yliu
>>> >
>>>
>>> I did tried similar in past but not in parse_sysfs (such that
>>> mem.resource_addr to accept IO_RESOURCE_IO types) and observed that
>>> pci_map_resource not able to map address hence segfault at tespmd
>>> initialization.
>>>
>>> i was getting these:
>>> EAL: pci_map_resource(): cannot mmap(19, 0x7fa5c00000, 0x20, 0x0):
>>> Invalid argument (0xffffffffffffffff)
>>
>> That's because ARM (at least the kernel) doesn't allow an IO map:
>>
>> arch/arm/kernel/bios32.c
>> ------------------------
>> 618 int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
>> 619                         enum pci_mmap_state mmap_state, int write_combine)
>> 620 {
>> 621         if (mmap_state == pci_mmap_io)
>> 622                 return -EINVAL;
>>
>> And with a quick glimpse of powerpc, I see no such limitation. Hence,
>> this peice of code may work only on Powerpc platform (and maybe a few
>> others we don't care).
>>
>> So, apparently, this will not work for ARM.
>>
>
> Right and I did shared detailed explanation on why it wont work on
> this link [1], infact this patch shouldn;t work for mips too.
>
> As I mentioned earlier I did tried similar approach and so to get
> everything working like iomem is currently in dpdk; we need to add
> something like pci_remap_iospace --> ioremap_page_range() but this api
> not really pci_mmap_page_range types. user need to write more code on
> top so to use this api efficiently, also this api looks like meant to
> use by arch file only in kernel space.
>
>
missed link;

[1] http://dpdk.org/dev/patchwork/patch/9365/

>>         --yliu