linux/Documentation/devicetree/bindings/arm/l2c2x0.txt

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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).
ARM: 8169/1: l2c: parse cache properties from ePAPR definitions When both 'cache-size' and 'cache-sets' are specified for a L2 cache controller node, parse those properties and set up the set size based on which type of L2 cache controller we are using. Update the L2 cache controller Device Tree binding with the optional 'cache-size', 'cache-sets', 'cache-block-size' and 'cache-line-size' properties. These come from the ePAPR specification. Using the cache size, number of sets and cache line size we can calculate desired associativity of the L2 cache. This is done by the calculation: set size = cache size / sets ways = set size / line size way size = cache size / ways = sets * line size associativity = cache size / way size Example output from the PB1176 DT that look like this: L2: l2-cache { compatible = "arm,l220-cache"; (...) arm,override-auxreg; cache-size = <131072>; // 128kB cache-sets = <512>; cache-line-size = <32>; }; Ends up like this: L2C OF: override cache size: 131072 bytes (128KB) L2C OF: override line size: 32 bytes L2C OF: override way size: 16384 bytes (16KB) L2C OF: override associativity: 8 L2C: DT/platform modifies aux control register: 0x02020fff -> 0x02030fff L2C-220 cache controller enabled, 8 ways, 128 kB L2C-220: CACHE_ID 0x41000486, AUX_CTRL 0x06030fff Which is consistent with the value earlier hardcoded for the PB1176 platform. This patch is an extended version based on the initial patch by Florian Fainelli. Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2014-09-26 08:01:58 +00:00
Some of the properties that are just prefixed "cache-*" are taken from section
3.7.3 of the ePAPR v1.1 specification which can be found at:
https://www.power.org/wp-content/uploads/2012/06/Power_ePAPR_APPROVED_v1.1.pdf
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: 8076/1: mm: add support for HW coherent systems in PL310 cache When a PL310 cache is used on a system that provides hardware coherency, the outer cache sync operation is useless, and can be skipped. Moreover, on some systems, it is harmful as it causes deadlocks between the Marvell coherency mechanism, the Marvell PCIe controller and the Cortex-A9. To avoid this, this commit introduces a new Device Tree property 'arm,io-coherent' for the L2 cache controller node, valid only for the PL310 cache. It identifies the usage of the PL310 cache in an I/O coherent configuration. Internally, it makes the driver disable the outer cache sync operation. Note that technically speaking, a fully coherent system wouldn't require any of the other .outer_cache operations. However, in practice, when booting secondary CPUs, these are not yet coherent, and therefore a set of cache maintenance operations are necessary at this point. This explains why we keep the other .outer_cache operations and only ->sync is disabled. While in theory any write to a PL310 register could cause the deadlock, in practice, disabling ->sync is sufficient to workaround the deadlock, since the other cache maintenance operations are only used in very specific situations. Contrary to previous versions of this patch, this new version does not simply NULL-ify the ->sync member, because the l2c_init_data structures are now 'const' and therefore cannot be modified, which is a good thing. Therefore, this patch introduces a separate l2c_init_data instance, called of_l2c310_coherent_data. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2014-06-13 09:58:38 +00:00
- 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.
ARM: 8169/1: l2c: parse cache properties from ePAPR definitions When both 'cache-size' and 'cache-sets' are specified for a L2 cache controller node, parse those properties and set up the set size based on which type of L2 cache controller we are using. Update the L2 cache controller Device Tree binding with the optional 'cache-size', 'cache-sets', 'cache-block-size' and 'cache-line-size' properties. These come from the ePAPR specification. Using the cache size, number of sets and cache line size we can calculate desired associativity of the L2 cache. This is done by the calculation: set size = cache size / sets ways = set size / line size way size = cache size / ways = sets * line size associativity = cache size / way size Example output from the PB1176 DT that look like this: L2: l2-cache { compatible = "arm,l220-cache"; (...) arm,override-auxreg; cache-size = <131072>; // 128kB cache-sets = <512>; cache-line-size = <32>; }; Ends up like this: L2C OF: override cache size: 131072 bytes (128KB) L2C OF: override line size: 32 bytes L2C OF: override way size: 16384 bytes (16KB) L2C OF: override associativity: 8 L2C: DT/platform modifies aux control register: 0x02020fff -> 0x02030fff L2C-220 cache controller enabled, 8 ways, 128 kB L2C-220: CACHE_ID 0x41000486, AUX_CTRL 0x06030fff Which is consistent with the value earlier hardcoded for the PB1176 platform. This patch is an extended version based on the initial patch by Florian Fainelli. Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2014-09-26 08:01:58 +00:00
- 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).
ARM: 8395/1: l2c: Add support for the "arm,shared-override" property "CoreLink Level 2 Cache Controller L2C-310", p. 2-15, section 2.3.2 Shareable attribute" states: "The default behavior of the cache controller with respect to the shareable attribute is to transform Normal Memory Non-cacheable transactions into: - cacheable no allocate for reads - write through no write allocate for writes." Depending on the system architecture, this may cause memory corruption in the presence of bus mastering devices (e.g. OHCI). To avoid such corruption, the default behavior can be disabled by setting the Shared Override bit in the Auxiliary Control register. Currently the Shared Override bit can be set only using C code: - by calling l2x0_init() directly, which is deprecated, - by setting/clearing the bit in the machine_desc.l2c_aux_val/mask fields, but using values differing from 0/~0 is also deprecated. Hence add support for an "arm,shared-override" device tree property for the l2c device node. By specifying this property, affected systems can indicate that non-cacheable transactions must not be transformed. Then, it's up to the OS to decide. The current behavior is to set the "shared attribute override enable" bit, as there may exist kernel linear mappings and cacheable aliases for the DMA buffers, even if CMA is enabled. See also commit 1a8e41cd672f894b ("ARM: 6395/1: VExpress: Set bit 22 in the PL310 (cache controller) AuxCtlr register"): "Clearing bit 22 in the PL310 Auxiliary Control register (shared attribute override enable) has the side effect of transforming Normal Shared Non-cacheable reads into Cacheable no-allocate reads. Coherent DMA buffers in Linux always have a Cacheable alias via the kernel linear mapping and the processor can speculatively load cache lines into the PL310 controller. With bit 22 cleared, Non-cacheable reads would unexpectedly hit such cache lines leading to buffer corruption." Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2015-06-26 07:09:29 +00:00
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)
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.