Re: [Patch v7 4/7] PCI/ACPI: Add interface acpi_pci_root_create()

Tomasz Nowicki
2015-11-12T13:21:28Z

On 12.11.2015 09:43, Jiang Liu wrote:
> On 2015/11/12 1:46, Lorenzo Pieralisi wrote:
>> On Tue, Nov 10, 2015 at 01:50:46PM +0800, Jiang Liu wrote:
>>
>> [...]
>>
>>>>> In particular, I would like to understand, for an eg DWordIO descriptor,
>>>>> what Range Minimum, Range Maximum and Translation Offset represent,
>>>>> they can't mean different things depending on the SW parsing them,
>>>>> this totally defeats the purpose.
>>>>
>>>> I have no clue about what those mean in ACPI though.
>>>>
>>>> Generally speaking, each PCI domain is expected to have a (normally 64KB)
>>>> range of CPU addresses that gets translated into PCI I/O space the same
>>>> way that config space and memory space are handled.
>>>> This is true for almost every architecture except for x86, which uses
>>>> different CPU instructions for I/O space compared to the other spaces.
>>>>
>>>>> By the way, ia64 ioremaps the translation_offset (ie new_space()), so
>>>>> basically that's the CPU physical address at which the PCI host bridge
>>>>> map the IO space transactions), I do not think ia64 is any different from
>>>>> arm64 in this respect, if it is please provide an HW description here from
>>>>> the PCI bus perspective here (also an example of ia64 ACPI PCI host bridge
>>>>> tables would help).
>>>>
>>>> The main difference between ia64 and a lot of the other architectures (e.g.
>>>> sparc is different again) is that ia64 defines a logical address range
>>>> in terms of having a small number for each I/O space followed by the
>>>> offset within that space as a 'port number' and uses a mapping function
>>>> that is defined as
>>>>
>>>> static inline void *__ia64_mk_io_addr (unsigned long port)
>>>> {
>>>> struct io_space *space = &io_space[IO_SPACE_NR(port)];
>>>> return (space->mmio_base | IO_SPACE_PORT(port););
>>>> }
>>>> static inline unsigned int inl(unsigned long port)
>>>> {
>>>> return *__ia64_mk_io_addr(port);
>>>> }
>>>>
>>>> Most architectures allow only one I/O port range and put it at a fixed
>>>> virtual address so that inl() simply becomes
>>>>
>>>> static inline u32 inl(unsigned long addr)
>>>> {
>>>> return readl(PCI_IOBASE + addr);
>>>> }
>>>>
>>>> which noticeably reduces code size.
>>>>
>>>> On some architectures (powerpc, arm, arm64), we then get the same simplified
>>>> definition with a fixed virtual address, and use pci_ioremap_io() or
>>>> something like that to to map a physical address range into this virtual
>>>> address window at the correct io_offset;
>>> Hi all,
>>> Thanks for explanation, I found a way to make the ACPI resource
>>> parsing interface arch neutral, it should help to address Lorenzo's
>>> concern. Please refer to the attached patch. (It's still RFC, not tested
>>> yet).
>>
>> If we go with this approach though, you are not adding the offset to
>> the resource when parsing the memory spaces in acpi_decode_space(), are we
>> sure that's what we really want ?
>>
>> In DT, a host bridge range has a:
>>
>> - CPU physical address
>> - PCI bus address
>>
>> We use that to compute the offset between primary bus (ie CPU physical
>> address) and secondary bus (ie PCI bus address).
>>
>> The value ending up in the PCI resource struct (for memory space) is
>> the CPU physical address, if you do not add the offset in acpi_decode_space
>> that does not hold true on platforms where CPU<->PCI offset != 0 on ACPI,
>> am I wrong ?
> Hi Lorenzo,
> I may have found the divergence between us about the design here. You
> treat it as a one-stage translation but I treat it as a
> two-stage translation as below:
> stage 1: map(translate) per-PCI-domain IO port address[0, 16M) into
> system global IO port address. Here system global IO port address is
> ioport_resource[0, IO_SPACE_LIMIT).
> stage 2: map system IO port address into system memory address.
>
> We need two objects of struct resource_win to support above two-stage
> translation. One object, type of IORESOURCE_IO, is used to support
> stage one, and it will also used to allocate IO port resources
> for PCI devices. Another object, type of IORESOURCE_MMIO, is used
> to allocate resource from iomem_resource and setup MMIO mapping
> to actually access IO ports.
>
> For ARM64, it doesn't support multiple per-PCI-domain(bus local)
> IO port address space yet, so stage one seems to be optional
> becomes the offset between bus local IO port address and system
> IO port address is always 0. But we still need two objects of
> struct resource_win. The first object is
> {
> offset:0,
> start:AddressMinimum,
> end:AddressMaximum,
> flags:IORESOURCE_IO
> }
> Here it's type of IORESOURCE_IO and offset must be zero because
> pcibios_resource_to_bus() will access it translate system IO
> port address into bus local IO port address. With my patch,
> the struct resource_win object created by the ACPI core will
> be reused for this.
>
> The second object is:
> {
> offset:Translation_Offset,
> start:AddressMinimum + Translation_Offset,
> end:AddressMaximum + Translation_Offset,
> flags:IORESOURCE_MMIO
> }
> Arch code need to create the second struct resource_win object
> and actually setup the MMIO mapping.
>
> But there's really another bug need to get fixed, funciton
> acpi_dev_ioresource_flags() assumes bus local IO port address
> space is size of 64K, which is wrong for IA64 and ARM64.
>

So what would be the Translation_Offset meaning for two cases DWordIo
(....,TypeTranslation) vs DWordIo (....,TypeStatic)? And why we did not
use TypeTranslation for IA64 so far?

I am worried that TypeTranslation fall into the IA64 category but ACPI
tables were already written incorrectly.

Tomasz