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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.
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