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Re: Reason for PIO_MASK?

To: Manuel Lauss <manuel.lauss@googlemail.com>
Subject: Re: Reason for PIO_MASK?
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Wed, 07 Oct 2009 19:49:08 +0400
Cc: Ralf Baechle <ralf@linux-mips.org>, Linux-MIPS <linux-mips@linux-mips.org>
In-reply-to: <f861ec6f0910060759v21ac3fe1k7cb130f427834742@mail.gmail.com>
Organization: MontaVista Software Inc.
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Hello.

Manuel Lauss wrote:

I meant the result of ioremap() of the 36bit address of PCMCIA IO space:
so the ioport base is somewhere at 0xc0000000, which pata_pcmcia
tries to devm_iomap(), and this is rejected by the above mentioned file.

The old ide-cs.c driver takes the given IO base as-is (without trying to
do funky things to it) and just works. (i.e. there are 2 entries in the
0xc0000000-range per cf-card in /proc/ioports)

Feeding a virtual address as input to devm_ioremap or ioremap does not
make sense.  Ioremap is only to be used for memory resources anyway.

Somewhere in the pcmcia socket driver I need to ioremap the 36bit
base of pcmcia io area:
io_base = ioremap(0xF 0000 0000, 0x10000) (->0xc1086000)

This is passed as io base to all drivers attached to this particular
pcmcia socket:

pata_pcmcia::pcmcia_init_one:
   devm_ioport_map(0xc1086000)
      ioport_map(0xc1086000) => no way!

But this is incorrect. You can't pass the result of ioremap to ioport_map() -- it's already a virtual *memory* address.

With 2 sockets I have 2 isolated IO bases, and so far this works as
expected, except on drivers which use ioport_map().

There's something up with either your code or these drivers -- as what you're trying to do is just mixing the memory vs I/O port and physical vs virtual addresses.

I've temporarily removed the PIO_MASK check and pata_pcmcia
works as expected. Is there any way around this, other than
creating an Alchemy-specific ioport_map() function?

The provocative question - why would you want to have more than 64k I/O port
space?

*I* don't want more; I want a smarter pata_pcmcia driver ;-)  I'll go bug other
people about this.  I brought this up here because one of my SH boards has
similar needs (need to do an ioremap() with special TLB flags to get access to
pcmcia IO space) but pata_pcmcia does work there (because SH kernel
either asks the board to translate an x86-IO port to memory address or
simply returns the port plus an offset).

Well, Alchemy does this:

...
      if (!virt_io_addr) {
              printk(KERN_ERR "Unable to ioremap pci space\n");
              return 1;
      }
      au1x_controller.io_map_base = virt_io_addr;
...
set_io_port_base(virt_io_addr);
...

Which sets up a mapping for the entire port space.  Normally the PCMCIA
I/O port space should also be part of this range so inb, outb etc. for
the low 64k or so of port address range should just work without further
iomap calls of any sort.

With this scheme, if I put CF cards in both sockets, I think I'm screwed,
since both cards will use the same io ports.

/proc/ioports with 2 cf cards, independet pcmcia sockets:
c1086000-c1086007 : ide-cs
c108600e-c108600e : ide-cs
c108a000-c108a007 : ide-cs
c108a00e-c108a00e : ide-cs

Of all non-x86 archs which implement ioport_map(), MIPS is the only one
which excplicitly checks the argument; most simply return it unchanged,

some adjust the address space (and complain), add an offset,
or ioremap it (AVR32).  Why is MIPS special in this regard?

Look at the default implementation in lib/iomap.c please -- it gets used when the arch doesn't implement ioport_map() and it makes use of PIO_MASK.

Maybe the whole logic should be turned around? Complain loudly if a driver
tries to access the range covered by PIO_MASK?

I didn't get the idea. PIO_MASK defined the *valid* address range for in*()/out*(), not invalid.

        Manuel Lauss

WBR, Sergei

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