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    SubjectRe: [PATCH V5 3/3] ARM64 LPC: LPC driver implementation on Hip06
    Hi Arnd,

    On Thu, Nov 10, 2016 at 05:07:21PM +0100, Arnd Bergmann wrote:
    > On Thursday, November 10, 2016 3:36:49 PM CET Gabriele Paoloni wrote:
    > >
    > > Where should we get the range from? For LPC we know that it is going
    > > Work on anything that is not used by PCI I/O space, and this is
    > > why we use [0, PCIBIOS_MIN_IO]
    >
    > It should be allocated the same way we allocate PCI config space
    > segments. This is currently done with the io_range list in
    > drivers/pci/pci.c, which isn't perfect but could be extended
    > if necessary. Based on what others commented here, I'd rather
    > make the differences between ISA/LPC and PCI I/O ranges smaller
    > than larger.
    >
    > > > Your current version has
    > > >
    > > > if (arm64_extio_ops->pfout) \
    > > > arm64_extio_ops->pfout(arm64_extio_ops->devpara,\
    > > > addr, value, sizeof(type)); \
    > > >
    > > > Instead, just subtract the start of the range from the logical
    > > > port number to transform it back into a bus-local port number:
    > >
    > > These accessors do not operate on IO tokens:
    > >
    > > If (arm64_extio_ops->start > addr || arm64_extio_ops->end < addr)
    > > addr is not going to be an I/O token; in fact patch 2/3 imposes that
    > > the I/O tokens will start at PCIBIOS_MIN_IO. So from 0 to PCIBIOS_MIN_IO
    > > we have free physical addresses that the accessors can operate on.
    >
    > Ah, I missed that part. I'd rather not use PCIBIOS_MIN_IO to refer to
    > the logical I/O tokens, the purpose of that macro is really meant
    > for allocating PCI I/O port numbers within the address space of
    > one bus.
    >
    > Note that it's equally likely that whichever next platform needs
    > non-mapped I/O access like this actually needs them for PCI I/O space,
    > and that will use it on addresses registered to a PCI host bridge.
    >
    > If we separate the two steps:
    >
    > a) assign a range of logical I/O port numbers to a bus

    Except that currently when we add ranges to io_range_list we don't have
    a bus number yet, because the parsing happens before the host bridge
    has been created. Maybe register_io_range() can take a bus number as an
    argument, but I'm not sure how we are going to use that in pci_pio_to_address()
    or pci_address_to_pio().

    Best regards,
    Liviu

    > b) register a set of helpers for redirecting logical I/O
    > port to a helper function
    >
    > then I think the code will get cleaner and more flexible.
    > It should actually then be able to replace the powerpc
    > specific implementation.
    >
    > Arnd

    --
    ====================
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    | fix the world, |
    | but they're not |
    | giving me the |
    \ source code! /
    ---------------
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