The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/powerpc/fsl/msi-pic.txt

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    1 * Freescale MSI interrupt controller
    2 
    3 Required properties:
    4 - compatible : compatible list, may contain one or two entries
    5   The first is "fsl,CHIP-msi", where CHIP is the processor(mpc8610, mpc8572,
    6   etc.) and the second is "fsl,mpic-msi" or "fsl,ipic-msi" or
    7   "fsl,mpic-msi-v4.3" depending on the parent type and version. If mpic
    8   version is 4.3, the number of MSI registers is increased to 16, MSIIR1 is
    9   provided to access these 16 registers, and compatible "fsl,mpic-msi-v4.3"
   10   should be used. The first entry is optional; the second entry is
   11   required.
   12 
   13 - reg : It may contain one or two regions. The first region should contain
   14   the address and the length of the shared message interrupt register set.
   15   The second region should contain the address of aliased MSIIR or MSIIR1
   16   register for platforms that have such an alias, if using MSIIR1, the second
   17   region must be added because different MSI group has different MSIIR1 offset.
   18 
   19 - interrupts : each one of the interrupts here is one entry per 32 MSIs,
   20   and routed to the host interrupt controller. the interrupts should
   21   be set as edge sensitive.  If msi-available-ranges is present, only
   22   the interrupts that correspond to available ranges shall be present.
   23 
   24 Optional properties:
   25 - msi-available-ranges: use <start count> style section to define which
   26   msi interrupt can be used in the 256 msi interrupts. This property is
   27   optional, without this, all the MSI interrupts can be used.
   28   Each available range must begin and end on a multiple of 32 (i.e.
   29   no splitting an individual MSI register or the associated PIC interrupt).
   30   MPIC v4.3 does not support this property because the 32 interrupts of an
   31   individual register are not continuous when using MSIIR1.
   32 
   33 - msi-address-64: 64-bit PCI address of the MSIIR register. The MSIIR register
   34   is used for MSI messaging.  The address of MSIIR in PCI address space is
   35   the MSI message address.
   36 
   37   This property may be used in virtualized environments where the hypervisor
   38   has created an alternate mapping for the MSIR block.  See below for an
   39   explanation.
   40 
   41 
   42 Example:
   43         msi@41600 {
   44                 compatible = "fsl,mpc8610-msi", "fsl,mpic-msi";
   45                 reg = <0x41600 0x80>;
   46                 msi-available-ranges = <0 0x100>;
   47                 interrupts = <
   48                         0xe0 0
   49                         0xe1 0
   50                         0xe2 0
   51                         0xe3 0
   52                         0xe4 0
   53                         0xe5 0
   54                         0xe6 0
   55                         0xe7 0>;
   56                 interrupt-parent = <&mpic>;
   57         };
   58 
   59         msi@41600 {
   60                 compatible = "fsl,mpic-msi-v4.3";
   61                 reg = <0x41600 0x200 0x44148 4>;
   62                 interrupts = <
   63                         0xe0 0 0 0
   64                         0xe1 0 0 0
   65                         0xe2 0 0 0
   66                         0xe3 0 0 0
   67                         0xe4 0 0 0
   68                         0xe5 0 0 0
   69                         0xe6 0 0 0
   70                         0xe7 0 0 0
   71                         0x100 0 0 0
   72                         0x101 0 0 0
   73                         0x102 0 0 0
   74                         0x103 0 0 0
   75                         0x104 0 0 0
   76                         0x105 0 0 0
   77                         0x106 0 0 0
   78                         0x107 0 0 0>;
   79         };
   80 
   81 The Freescale hypervisor and msi-address-64
   82 -------------------------------------------
   83 Normally, PCI devices have access to all of CCSR via an ATMU mapping.  The
   84 Freescale MSI driver calculates the address of MSIIR (in the MSI register
   85 block) and sets that address as the MSI message address.
   86 
   87 In a virtualized environment, the hypervisor may need to create an IOMMU
   88 mapping for MSIIR.  The Freescale ePAPR hypervisor has this requirement
   89 because of hardware limitations of the Peripheral Access Management Unit
   90 (PAMU), which is currently the only IOMMU that the hypervisor supports.
   91 The ATMU is programmed with the guest physical address, and the PAMU
   92 intercepts transactions and reroutes them to the true physical address.
   93 
   94 In the PAMU, each PCI controller is given only one primary window.  The
   95 PAMU restricts DMA operations so that they can only occur within a window.
   96 Because PCI devices must be able to DMA to memory, the primary window must
   97 be used to cover all of the guest's memory space.
   98 
   99 PAMU primary windows can be divided into 256 subwindows, and each
  100 subwindow can have its own address mapping ("guest physical" to "true
  101 physical").  However, each subwindow has to have the same alignment, which
  102 means they cannot be located at just any address.  Because of these
  103 restrictions, it is usually impossible to create a 4KB subwindow that
  104 covers MSIIR where it's normally located.
  105 
  106 Therefore, the hypervisor has to create a subwindow inside the same
  107 primary window used for memory, but mapped to the MSIR block (where MSIIR
  108 lives).  The first subwindow after the end of guest memory is used for
  109 this.  The address specified in the msi-address-64 property is the PCI
  110 address of MSIIR.  The hypervisor configures the PAMU to map that address to
  111 the true physical address of MSIIR.

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