xref: /kernel/linux/linux-5.10/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.txt

Embedded Memory Controller

Properties:
- name : Should be emc
- #address-cells : Should be 1
- #size-cells : Should be 0
- compatible : Should contain "nvidia,tegra20-emc".
- reg : Offset and length of the register set for the device
- nvidia,use-ram-code : If present, the sub-nodes will be addressed
  and chosen using the ramcode board selector. If omitted, only one
  set of tables can be present and said tables will be used
  irrespective of ram-code configuration.
- interrupts : Should contain EMC General interrupt.
- clocks : Should contain EMC clock.

Child device nodes describe the memory settings for different configurations and clock rates.

Example:

	memory-controller@7000f400 {
		#address-cells = < 1 >;
		#size-cells = < 0 >;
		compatible = "nvidia,tegra20-emc";
		reg = <0x7000f4000 0x200>;
		interrupts = <0 78 0x04>;
		clocks = <&tegra_car TEGRA20_CLK_EMC>;
	}


Embedded Memory Controller ram-code table

If the emc node has the nvidia,use-ram-code property present, then the
next level of nodes below the emc table are used to specify which settings
apply for which ram-code settings.

If the emc node lacks the nvidia,use-ram-code property, this level is omitted
and the tables are stored directly under the emc node (see below).

Properties:

- name : Should be emc-tables
- nvidia,ram-code : the binary representation of the ram-code board strappings
  for which this node (and children) are valid.



Embedded Memory Controller configuration table

This is a table containing the EMC register settings for the various
operating speeds of the memory controller. They are always located as
subnodes of the emc controller node.

There are two ways of specifying which tables to use:

* The simplest is if there is just one set of tables in the device tree,
  and they will always be used (based on which frequency is used).
  This is the preferred method, especially when firmware can fill in
  this information based on the specific system information and just
  pass it on to the kernel.

* The slightly more complex one is when more than one memory configuration
  might exist on the system.  The Tegra20 platform handles this during
  early boot by selecting one out of possible 4 memory settings based
  on a 2-pin "ram code" bootstrap setting on the board. The values of
  these strappings can be read through a register in the SoC, and thus
  used to select which tables to use.

Properties:
- name : Should be emc-table
- compatible : Should contain "nvidia,tegra20-emc-table".
- reg : either an opaque enumerator to tell different tables apart, or
  the valid frequency for which the table should be used (in kHz).
- clock-frequency : the clock frequency for the EMC at which this
  table should be used (in kHz).
- nvidia,emc-registers : a 46 word array of EMC registers to be programmed
  for operation at the 'clock-frequency' setting.
  The order and contents of the registers are:
    RC, RFC, RAS, RP, R2W, W2R, R2P, W2P, RD_RCD, WR_RCD, RRD, REXT,
    WDV, QUSE, QRST, QSAFE, RDV, REFRESH, BURST_REFRESH_NUM, PDEX2WR,
    PDEX2RD, PCHG2PDEN, ACT2PDEN, AR2PDEN, RW2PDEN, TXSR, TCKE, TFAW,
    TRPAB, TCLKSTABLE, TCLKSTOP, TREFBW, QUSE_EXTRA, FBIO_CFG6, ODT_WRITE,
    ODT_READ, FBIO_CFG5, CFG_DIG_DLL, DLL_XFORM_DQS, DLL_XFORM_QUSE,
    ZCAL_REF_CNT, ZCAL_WAIT_CNT, AUTO_CAL_INTERVAL, CFG_CLKTRIM_0,
    CFG_CLKTRIM_1, CFG_CLKTRIM_2

		emc-table@166000 {
			reg = <166000>;
			compatible = "nvidia,tegra20-emc-table";
			clock-frequency = < 166000 >;
			nvidia,emc-registers = < 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 >;
		};

		emc-table@333000 {
			reg = <333000>;
			compatible = "nvidia,tegra20-emc-table";
			clock-frequency = < 333000 >;
			nvidia,emc-registers = < 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 0 0 0 0 0 0 0 0 0 0
						 0 0 0 0 >;
		};