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Date:      Fri, 17 Jul 2009 21:04:50 +0200
From:      Andre Albsmeier <Andre.Albsmeier@siemens.com>
To:        freebsd-hackers@freebsd.org
Cc:        Rui Paulo <rpaulo@freebsd.org>, Andre.Albsmeier@siemens.com
Subject:   Reading acpi memory from a driver attached to hostb
Message-ID:  <20090717190450.GA4697@curry.mchp.siemens.de>
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[CC'ing this to Rui Paulo since he tried to help me a while ago]

I have written a driver that is a child of hostb (similar to agp) for
RELENG_7. However, on some chipsets (e.g. i975) it has to read some
memory locations (not pci configuration space) which were registered
by acpi as system resources.

Since my driver is a child of hostb0, I have no idea of how to access
this memory area. Here is a devinfo -r to make things clear:

nexus0
  acpi0
      Interrupt request lines:
          9
      I/O ports:
          0x10-0x1f
          0x22-0x3f
          ...
          0x800-0x87f
      I/O memory addresses:
          0xc0000-0xdffff
          0xe0000-0xfffff
          0xf0000000-0xf3ffffff
          0xfec00000-0xfec00fff
          0xfed13000-0xfed19fff		<--- the memory needed
          0xfed1c000-0xfed1ffff
          ....
          0xfed20000-0xfed3ffff
          0xfff00000-0xffffffff
    cpu0
      coretemp0
      acpi_throttle0
          ACPI I/O ports:
              0x810-0x813
      cpufreq0
    cpu1
      coretemp1
    pcib0
      pci0
          I/O ports:
              0x170-0x177
              0x376
        hostb0
            I/O memory addresses:
                0xe4000000-0xe7ffffff
          MYDRIVER0                      <--- my driver
          agp0
        pcib1
          pci7
            vgapci0
                Interrupt request lines:
                    16

I had the same problem under RELENG_6 six month ago which could be
solved by a bus_set_resource() but since the driver now attaches to
hostb, this is not possible anymore.

Earlier, I was given the hint to attach as a child of acpi (see the
old mail attached below) but in this case I didn't have access to the
hostb registers which I need as well.

The only thing I see is: Attach two drivers -- one as child of acpi
and another as child of hostb and let them communicate somehow (no
idea how to do this).

I have also done crazy things like searching for acpi0 and trying
to bus_alloc_resource() the memory I am interested in but this also
failed.

Or is it possible to free(!) somehow the address space from acpi0
and pass it to hostb0 so I can bus_alloc_resource() it?

Thanks a lot for all ideas,

	-Andre

------------------------------------------------------------------

> Hello all,
>
> I am writing a driver which needs to access memory at a
> specific location. The location depends on what the BIOS
> has configured into the host bridge. For example, my
> current machine uses an Intel 975X chipset and the memory
> location I am interested in has been set to 0xFED14000 and
> is 16KB in size (this is MCHBAR of the 975X memory hub).

You probably just need to do something like:

rid = PCI_BAR(number);
res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid, RF_ACTIVE);

And then,
bus_read_4(res, offset from specified PCI BAR);

>
>
> I have no idea how to access this space from my driver.
> I have played around with bus_alloc_resource() but this
> only gives me back NULL.
>
> However, a devinfo -r gives me:
>
> nexus0
>  npx0
>  acpi0
>      Interrupt request lines:
>          9
>      I/O ports:
>          0x10-0x1f
> ...
>          0x800-0x87f
>      I/O memory addresses:
>          0x0-0x9ffff
>          0xc0000-0xdffff
>          0xe0000-0xfffff
>          0x100000-0x7fffffff
>          0xf0000000-0xf3ffffff
>          0xfec00000-0xfec00fff
>          0xfed13000-0xfed19fff		<---
>          0xfed1c000-0xfed1ffff
>          0xfed20000-0xfed3ffff
>          0xfed50000-0xfed8ffff
>          0xfee00000-0xfee00fff
>          0xffb00000-0xffbfffff
>          0xfff00000-0xffffffff
>    cpu0
> ...
>
> The line marked with <--- shows the range which includes
> the location I am interested in. It is probably assigned
> to the acpi0 device.
>
> How do I proceed from this? Do I have to hack around in
> the ACPI-Code? I don't hope so ;-)

You'll probably need to create a fake ACPI child driver to access it.

Create your identify routine with something like:

static void mydriver_identify(driver_t *driver, device_t parent)
{
	if (device_find_child(parent, "mydriver", -1) == NULL &&
	    mydriver_match(parent))
		device_add_child(parent, "mydriver", -1);
}

mydriver_match() should check if you were given the acpi0 device.


Regards,
--
Rui Paulo

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