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