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Date:      Thu, 19 Mar 2015 13:58:54 -0300
From:      =?UTF-8?Q?Mat=C3=ADas_Perret_Cantoni?= <perretcantonim@gmail.com>
To:        freebsd-arm@freebsd.org
Subject:   Zynq-7020 SoC on-chip-memory
Message-ID:  <CADLKG01oSQ=caZFOnZQM14=pAVPvLz45EznMes9mVfG2kD6TEQ@mail.gmail.com>
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Hi everyone.

The board I'm using (Zedboard) has a Zynq-7020 SoC which has 256KB of
on-chip-memory (OCM) with execute-in-place capabilities.
I'd like to add this memory as part of the system memory, but either I
can't add it, or I don't know how to "see it".

Please let me know if this is not the right place to make this kind of
questions, I'll try to clarify myself:

First of all I've checked all the registers that defines the memory mapping
and the address filtering behavior of the Snoop Control Unit, and it looks
like both CPUs sees this memory map:

 0x0010_0000        0x1FF0_0000      0xFFFC_0000      0xFFFF_FFFF
/                             /                           /
       /
+++++++++++++++++++++++++++++++
|                           |****************|                          |
|       511MB         |****************|     256KB          |
|  (off chip RAM)  |****************| (on chip RAM)  |
|                           |****************|                          |
+++++++++++++++++++++++++++++++

(I believe Thomas Skibo can easily correct me here)

So far I modified the memory node of the dts file: The ePAPR specification
says that If a system has multiple memory ranges one can create multiple
memory nodes or just specify the ranges in the reg property of a single
memory node.

The memory node of the dts file in HEAD is:

  memory {
  // First megabyte isn't accessible by all interconnect masters.
  device_type = "memory";
  reg = <0x100000 0x1ff00000>;  /* 511MB RAM at 0x100000 */
  };

My first attempt was to modify the reg property of the memory node:

  memory {
  device_type = "memory";
  reg = <0x100000 0x1ff00000>,    /* 511MB RAM at 0x100000 */
  <0xFFFC0000 0x3FFFF>;  /* 256KB on-chip-memory at 0xfffc0000 */
  };

But the system hangs during boot. Then I tried to add a second memory node
for the on-chip-mem:


  memory@100000 {   // DDR3 RAM off-chip
        device_type = "memory";
        reg = <0x100000 0x1ff00000>; /* 511MB RAM at 0x100000 */
  };


  memory@FFFC0000 {    // On-Chip-Memory
        device_type = "memory";
        reg = <0xFFFC0000 0x3FFFF>;  /* 256KB at 0xFFFC0000 */
  };
In this case the system boots ok but I still see 511MB of system memory:

root@zedboard:~ # dmesg | grep memory
real memory  = 535822336 (511 MB)
avail memory = 515801088 (491 MB)

db> show physmem
Physical memory chunk(s):
  0x00100000 - 0x1fffffff,   511 MB ( 130816 pages)
Excluded memory regions:
  0x00100000 - 0x007effff,     6 MB (   1776 pages) NoAlloc


(Maybe I'm not checking properly :/ )

------
As an attempt to check If I can access this memory I added a device node in
the dts that represents the on-chip-memory. This isn't really useful but at
least I was able to read/write the memory with a simple newbus character
driver. The dts node I added is:

  ocm_area@FFFC0000 {
     device_type = "soc";
     compatible = "simple-bus";
     #address-cells = <1>;
     #size-cells = <1>;
     ranges = <0x0 0xFFFC0000 0x3FFFF>;   // OCM: 256KB

     ocm: ocm@0 {
           compatible = "lac,ocm";
           reg = <0x0 0xFF>;  // First 128Bytes of OCM
     };

So the driver gets the resources:

root@zedboard:/boot/msdos # devinfo -r | head
nexus0
  ofwbus0
    simplebus0
      ocm_driver0
          Device Memory:
              0xfffc0000-0xfffc00fe

But here I would expected that the device's memory range
(0xfffc0000-0xfffcffff) was included in the devmap's ranges, but it's not:

db> show devmap
Static device mappings:
  0xe0000000 - 0xe02fffff mapped at VA 0xffc00000
  0xf8000000 - 0xf8ffffff mapped at VA 0xfec00000


So I can't inspect the on-chip-memory range from the debugger either.

Any advice on how to add this memory to my system?



Thanks for you time and patience.
Regards,
Matias.

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