dt-bindings: PCI: dwc: Add reg/reg-names common properties

Even though there is a more-or-less limited set of the CSR spaces can be
defined for each DW PCIe controller the generic DT-schema currently
doesn't specify much limitations on the reg-space names used for one or
another range. In order to prevent the vendor-specific controller schemas
further deviation from the generic interface let's fix that by introducing
the reg-names definition in the common DW PCIe DT-schemas and preserving
the generic "reg" and "reg-names" properties in there. New DW PCIe device
DT-bindings are encouraged to use the generic set of the CSR spaces
defined in the generic DW PCIe RP/EP DT-bindings, while the already
available vendor-specific DT-bindings can still apple the common
DT-schemas.

Note the number of reg/reg-names items need to be changed in the DW PCIe
EP DT-schema since aside with the "dbi" CSRs space these arrays can have
"dbi2", "addr_space", "atu", etc ranges.

Also note since there are DW PCIe-based vendor-specific DT-bindings with
the custom names assigned to the same CSR resources we have no much choice
but to add them to the generic DT-schemas in order to have the schemas
being applicable for such devices. These names are marked as
vendor-specific and should be avoided being used in new bindings in favor
of the generic names.

Link: https://lore.kernel.org/r/20221113191301.5526-11-Sergey.Semin@baikalelectronics.ruSigned-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/snps,dw-pcie-common.yaml

@@ -17,6 +17,28 @@ description:
 select: false
 
 properties:
+  reg:
+    description:
+      DWC PCIe CSR space is normally accessed over the dedicated Data Bus
+      Interface - DBI. In accordance with the reference manual the register
+      configuration space belongs to the Configuration-Dependent Module (CDM)
+      and is split up into several sub-parts Standard PCIe configuration
+      space, Port Logic Registers (PL), Shadow Config-space Registers,
+      iATU/eDMA registers. The particular sub-space is selected by the
+      CDM/ELBI (dbi_cs) and CS2 (dbi_cs2) signals (selector bits). Such
+      configuration provides a flexible interface for the system engineers to
+      either map the particular space at a desired MMIO address or just leave
+      them in a contiguous memory space if pure Native or AXI Bridge DBI access
+      is selected. Note the PCIe CFG-space, PL and Shadow registers are
+      specific for each activated function, while the rest of the sub-spaces
+      are common for all of them (if there are more than one).
+    minItems: 2
+    maxItems: 6
+
+  reg-names:
+    minItems: 2
+    maxItems: 6
+
   interrupts:
     description:
       There are two main sub-blocks which are normally capable of

Documentation/devicetree/bindings/pci/snps,dw-pcie-ep.yaml

@@ -28,18 +28,86 @@ allOf:
 
 properties:
   reg:
-    description: |
-      It should contain Data Bus Interface (dbi) and config registers for all
-      versions.
-      For designware core version >= 4.80, it may contain ATU address space.
+    description:
+      DBI, DBI2 reg-spaces and outbound memory window are required for the
+      normal controller functioning. iATU memory IO region is also required
+      if the space is unrolled (IP-core version >= 4.80a).
     minItems: 2
-    maxItems: 4
+    maxItems: 5
 
   reg-names:
     minItems: 2
-    maxItems: 4
+    maxItems: 5
     items:
-      enum: [dbi, dbi2, config, atu, addr_space, link, atu_dma, appl]
+      oneOf:
+        - description:
+            Basic DWC PCIe controller configuration-space accessible over
+            the DBI interface. This memory space is either activated with
+            CDM/ELBI = 0 and CS2 = 0 or is a contiguous memory region
+            with all spaces. Note iATU/eDMA CSRs are indirectly accessible
+            via the PL viewports on the DWC PCIe controllers older than
+            v4.80a.
+          const: dbi
+        - description:
+            Shadow DWC PCIe config-space registers. This space is selected
+            by setting CDM/ELBI = 0 and CS2 = 1. This is an intermix of
+            the PCI-SIG PCIe CFG-space with the shadow registers for some
+            PCI Header space, PCI Standard and Extended Structures. It's
+            mainly relevant for the end-point controller configuration,
+            but still there are some shadow registers available for the
+            Root Port mode too.
+          const: dbi2
+        - description:
+            External Local Bus registers. It's an application-dependent
+            registers normally defined by the platform engineers. The space
+            can be selected by setting CDM/ELBI = 1 and CS2 = 0 wires or can
+            be accessed over some platform-specific means (for instance
+            as a part of a system controller).
+          enum: [ elbi, app ]
+        - description:
+            iATU/eDMA registers common for all device functions. It's an
+            unrolled memory space with the internal Address Translation
+            Unit and Enhanced DMA, which is selected by setting CDM/ELBI = 1
+            and CS2 = 1. For IP-core releases prior v4.80a, these registers
+            have been programmed via an indirect addressing scheme using a
+            set of viewport CSRs mapped into the PL space. Note iATU is
+            normally mapped to the 0x0 address of this region, while eDMA
+            is available at 0x80000 base address.
+          const: atu
+        - description:
+            Platform-specific eDMA registers. Some platforms may have eDMA
+            CSRs mapped in a non-standard base address. The registers offset
+            can be changed or the MS/LS-bits of the address can be attached
+            in an additional RTL block before the MEM-IO transactions reach
+            the DW PCIe slave interface.
+          const: dma
+        - description:
+            PHY/PCS configuration registers. Some platforms can have the
+            PCS and PHY CSRs accessible over a dedicated memory mapped
+            region, but mainly these registers are indirectly accessible
+            either by means of the embedded PHY viewport schema or by some
+            platform-specific method.
+          const: phy
+        - description:
+            Outbound iATU-capable memory-region which will be used to
+            generate various application-specific traffic on the PCIe bus
+            hierarchy. It's usage scenario depends on the endpoint
+            functionality, for instance it can be used to create MSI(X)
+            messages.
+          const: addr_space
+        - description:
+            Vendor-specific CSR names. Consider using the generic names above
+            for new bindings.
+          oneOf:
+            - description: See native 'elbi/app' CSR region for details.
+              enum: [ link, appl ]
+            - description: See native 'atu' CSR region for details.
+              enum: [ atu_dma ]
+    allOf:
+      - contains:
+          const: dbi
+      - contains:
+          const: addr_space
 
   interrupts:
     description:

Documentation/devicetree/bindings/pci/snps,dw-pcie.yaml

@@ -28,10 +28,10 @@ allOf:
 
 properties:
   reg:
-    description: |
-      It should contain Data Bus Interface (dbi) and config registers for all
-      versions.
-      For designware core version >= 4.80, it may contain ATU address space.
+    description:
+      At least DBI reg-space and peripheral devices CFG-space outbound window
+      are required for the normal controller work. iATU memory IO region is
+      also required if the space is unrolled (IP-core version >= 4.80a).
     minItems: 2
     maxItems: 5
 
@@ -39,8 +39,74 @@ properties:
     minItems: 2
     maxItems: 5
     items:
-      enum: [ dbi, dbi2, config, atu, atu_dma, app, appl, elbi, mgmt, ctrl,
-              parf, cfg, link, ulreg, smu, mpu, apb, phy ]
+      oneOf:
+        - description:
+            Basic DWC PCIe controller configuration-space accessible over
+            the DBI interface. This memory space is either activated with
+            CDM/ELBI = 0 and CS2 = 0 or is a contiguous memory region
+            with all spaces. Note iATU/eDMA CSRs are indirectly accessible
+            via the PL viewports on the DWC PCIe controllers older than
+            v4.80a.
+          const: dbi
+        - description:
+            Shadow DWC PCIe config-space registers. This space is selected
+            by setting CDM/ELBI = 0 and CS2 = 1. This is an intermix of
+            the PCI-SIG PCIe CFG-space with the shadow registers for some
+            PCI Header space, PCI Standard and Extended Structures. It's
+            mainly relevant for the end-point controller configuration,
+            but still there are some shadow registers available for the
+            Root Port mode too.
+          const: dbi2
+        - description:
+            External Local Bus registers. It's an application-dependent
+            registers normally defined by the platform engineers. The space
+            can be selected by setting CDM/ELBI = 1 and CS2 = 0 wires or can
+            be accessed over some platform-specific means (for instance
+            as a part of a system controller).
+          enum: [ elbi, app ]
+        - description:
+            iATU/eDMA registers common for all device functions. It's an
+            unrolled memory space with the internal Address Translation
+            Unit and Enhanced DMA, which is selected by setting CDM/ELBI = 1
+            and CS2 = 1. For IP-core releases prior v4.80a, these registers
+            have been programmed via an indirect addressing scheme using a
+            set of viewport CSRs mapped into the PL space. Note iATU is
+            normally mapped to the 0x0 address of this region, while eDMA
+            is available at 0x80000 base address.
+          const: atu
+        - description:
+            Platform-specific eDMA registers. Some platforms may have eDMA
+            CSRs mapped in a non-standard base address. The registers offset
+            can be changed or the MS/LS-bits of the address can be attached
+            in an additional RTL block before the MEM-IO transactions reach
+            the DW PCIe slave interface.
+          const: dma
+        - description:
+            PHY/PCS configuration registers. Some platforms can have the
+            PCS and PHY CSRs accessible over a dedicated memory mapped
+            region, but mainly these registers are indirectly accessible
+            either by means of the embedded PHY viewport schema or by some
+            platform-specific method.
+          const: phy
+        - description:
+            Outbound iATU-capable memory-region which will be used to access
+            the peripheral PCIe devices configuration space.
+          const: config
+        - description:
+            Vendor-specific CSR names. Consider using the generic names above
+            for new bindings.
+          oneOf:
+            - description: See native 'elbi/app' CSR region for details.
+              enum: [ apb, mgmt, link, ulreg, appl ]
+            - description: See native 'atu' CSR region for details.
+              enum: [ atu_dma ]
+            - description: Syscon-related CSR regions.
+              enum: [ smu, mpu ]
+    allOf:
+      - contains:
+          const: dbi
+      - contains:
+          const: config
 
   interrupts:
     description: