Documentation: dts: Add pl310 cache controller dts documentation

Linux commit 8ecd7f5970c5 ("ARM: 8483/1: Documentation: l2c: Rename
l2cc to l2c2x0")

Linux docs:
Documentation/devicetree/bindings/arm/l2c2x0.txt

Copied from Linux kernel v5.0.

"The documentation in the l2cc.txt is specific to the L2 cache
controllers L2C210/L2C220/L2C310 (also known as PL210/PL220/PL310
and variants) and not generic as the file name implies. It's not
valid for integrated L2 controllers as found in e.g.
Cortex-A15/A7/A57/A53."

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>

1 files changed, 114 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/arm/l2c2x0.txt b/Documentation/devicetree/bindings/arm/l2c2x0.txt
new file mode 100644
index 0000000..fbe6cb2
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+* ARM L2 Cache Controller
+
+ARM cores often have a separate L2C210/L2C220/L2C310 (also known as PL210/PL220/
+PL310 and variants) based level 2 cache controller. All these various implementations
+of the L2 cache controller have compatible programming models (Note 1).
+Some of the properties that are just prefixed "cache-*" are taken from section
+3.7.3 of the Devicetree Specification which can be found at:
+https://www.devicetree.org/specifications/
+
+The ARM L2 cache representation in the device tree should be done as follows:
+
+Required properties:
+
+- compatible : should be one of:
+  "arm,pl310-cache"
+  "arm,l220-cache"
+  "arm,l210-cache"
+  "bcm,bcm11351-a2-pl310-cache": DEPRECATED by "brcm,bcm11351-a2-pl310-cache"
+  "brcm,bcm11351-a2-pl310-cache": For Broadcom bcm11351 chipset where an
+     offset needs to be added to the address before passing down to the L2
+     cache controller
+  "marvell,aurora-system-cache": Marvell Controller designed to be
+     compatible with the ARM one, with system cache mode (meaning
+     maintenance operations on L1 are broadcasted to the L2 and L2
+     performs the same operation).
+  "marvell,aurora-outer-cache": Marvell Controller designed to be
+     compatible with the ARM one with outer cache mode.
+  "marvell,tauros3-cache": Marvell Tauros3 cache controller, compatible
+     with arm,pl310-cache controller.
+- cache-unified : Specifies the cache is a unified cache.
+- cache-level : Should be set to 2 for a level 2 cache.
+- reg : Physical base address and size of cache controller's memory mapped
+  registers.
+
+Optional properties:
+
+- arm,data-latency : Cycles of latency for Data RAM accesses. Specifies 3 cells of
+  read, write and setup latencies. Minimum valid values are 1. Controllers
+  without setup latency control should use a value of 0.
+- arm,tag-latency : Cycles of latency for Tag RAM accesses. Specifies 3 cells of
+  read, write and setup latencies. Controllers without setup latency control
+  should use 0. Controllers without separate read and write Tag RAM latency
+  values should only use the first cell.
+- arm,dirty-latency : Cycles of latency for Dirty RAMs. This is a single cell.
+- arm,filter-ranges : <start length> Starting address and length of window to
+  filter. Addresses in the filter window are directed to the M1 port. Other
+  addresses will go to the M0 port.
+- arm,io-coherent : indicates that the system is operating in an hardware
+  I/O coherent mode. Valid only when the arm,pl310-cache compatible
+  string is used.
+- interrupts : 1 combined interrupt.
+- cache-size : specifies the size in bytes of the cache
+- cache-sets : specifies the number of associativity sets of the cache
+- cache-block-size : specifies the size in bytes of a cache block
+- cache-line-size : specifies the size in bytes of a line in the cache,
+  if this is not specified, the line size is assumed to be equal to the
+  cache block size
+- cache-id-part: cache id part number to be used if it is not present
+  on hardware
+- wt-override: If present then L2 is forced to Write through mode
+- arm,double-linefill : Override double linefill enable setting. Enable if
+  non-zero, disable if zero.
+- arm,double-linefill-incr : Override double linefill on INCR read. Enable
+  if non-zero, disable if zero.
+- arm,double-linefill-wrap : Override double linefill on WRAP read. Enable
+  if non-zero, disable if zero.
+- arm,prefetch-drop : Override prefetch drop enable setting. Enable if non-zero,
+  disable if zero.
+- arm,prefetch-offset : Override prefetch offset value. Valid values are
+  0-7, 15, 23, and 31.
+- arm,shared-override : The default behavior of the L220 or PL310 cache
+  controllers with respect to the shareable attribute is to transform "normal
+  memory non-cacheable transactions" into "cacheable no allocate" (for reads)
+  or "write through no write allocate" (for writes).
+  On systems where this may cause DMA buffer corruption, this property must be
+  specified to indicate that such transforms are precluded.
+- arm,parity-enable : enable parity checking on the L2 cache (L220 or PL310).
+- arm,parity-disable : disable parity checking on the L2 cache (L220 or PL310).
+- arm,outer-sync-disable : disable the outer sync operation on the L2 cache.
+  Some core tiles, especially ARM PB11MPCore have a faulty L220 cache that
+  will randomly hang unless outer sync operations are disabled.
+- prefetch-data : Data prefetch. Value: <0> (forcibly disable), <1>
+  (forcibly enable), property absent (retain settings set by firmware)
+- prefetch-instr : Instruction prefetch. Value: <0> (forcibly disable),
+  <1> (forcibly enable), property absent (retain settings set by
+  firmware)
+- arm,dynamic-clock-gating : L2 dynamic clock gating. Value: <0> (forcibly
+  disable), <1> (forcibly enable), property absent (OS specific behavior,
+  preferably retain firmware settings)
+- arm,standby-mode: L2 standby mode enable. Value <0> (forcibly disable),
+  <1> (forcibly enable), property absent (OS specific behavior,
+  preferably retain firmware settings)
+- arm,early-bresp-disable : Disable the CA9 optimization Early BRESP (PL310)
+- arm,full-line-zero-disable : Disable the CA9 optimization Full line of zero
+  write (PL310)
+
+Example:
+
+L2: cache-controller {
+        compatible = "arm,pl310-cache";
+        reg = <0xfff12000 0x1000>;
+        arm,data-latency = <1 1 1>;
+        arm,tag-latency = <2 2 2>;
+        arm,filter-ranges = <0x80000000 0x8000000>;
+        cache-unified;
+        cache-level = <2>;
+	interrupts = <45>;
+};
+
+Note 1: The description in this document doesn't apply to integrated L2
+	cache controllers as found in e.g. Cortex-A15/A7/A57/A53. These
+	integrated L2 controllers are assumed to be all preconfigured by
+	early secure boot code. Thus no need to deal with their configuration
+	in the kernel at all.