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-README on the SDRAM Controller for the LH7a40X
-==============================================
-
-The standard configuration for the SDRAM controller generates a sparse
-memory array. The precise layout is determined by the SDRAM chips. A
-default kernel configuration assembles the discontiguous memory
-regions into separate memory nodes via the NUMA (Non-Uniform Memory
-Architecture) facilities. In this default configuration, the kernel
-is forgiving about the precise layout. As long as it is given an
-accurate picture of available memory by the bootloader the kernel will
-execute correctly.
-
-The SDRC supports a mode where some of the chip select lines are
-swapped in order to make SDRAM look like a synchronous ROM. Setting
-this bit means that the RAM will present as a contiguous array. Some
-programmers prefer this to the discontiguous layout. Be aware that
-may be a penalty for this feature where some some configurations of
-memory are significantly reduced; i.e. 64MiB of RAM appears as only 32
-MiB.
-
-There are a couple of configuration options to override the default
-behavior. When the SROMLL bit is set and memory appears as a
-contiguous array, there is no reason to support NUMA.
-CONFIG_LH7A40X_CONTIGMEM disables NUMA support. When physical memory
-is discontiguous, the memory tables are organized such that there are
-two banks per nodes with a small gap between them. This layout wastes
-some kernel memory for page tables representing non-existent memory.
-CONFIG_LH7A40X_ONE_BANK_PER_NODE optimizes the node tables such that
-there are no gaps. These options control the low level organization
-of the memory management tables in ways that may prevent the kernel
-from booting or may cause the kernel to allocated excessively large
-page tables. Be warned. Only change these options if you know what
-you are doing. The default behavior is a reasonable compromise that
-will suit all users.
-
---
-
-A typical 32MiB system with the default configuration options will
-find physical memory managed as follows.
-
- node 0: 0xc0000000 4MiB
- 0xc1000000 4MiB
- node 1: 0xc4000000 4MiB
- 0xc5000000 4MiB
- node 2: 0xc8000000 4MiB
- 0xc9000000 4MiB
- node 3: 0xcc000000 4MiB
- 0xcd000000 4MiB
-
-Setting CONFIG_LH7A40X_ONE_BANK_PER_NODE will put each bank into a
-separate node.