Memory organization (Naon)

Info Box Applies to Naon Applies to Maya Applies to Dido

Introduction

Naon memory organization and mapping is quite complex, due to DM8148's multiprocessor nature and the availability of several memory devices connected to the processor. This section will provide an overview of such architecture while following sections will describe in more detail memory map for each device. Please refer to Naon block diagram.

About system RAM, DM8148 provides two controllers. Each one can be interfaced to one SDRAM bank through a physical interface called EMIF (EMIF0 and EMIF1). EMIF0 is connected to 32-bit DDR2 SDRAM bank (up to 512 MByte). EMIF1 is not connected to any device, hence is permanently disabled.

About non-volatile memories, the following devices populate Naon module:

• SPI NOR flash
  • connected to SPI0 port
  • by default acts as boot memory
  • maximum size: up to 64 MByte
• NAND flash
  • connected to GPMC bus (CS0n)
  • optionally can act as boot memory
• EEPROM
  • connected to I2C3 bus.

NELK memory maps

This section describes in detail default memories mapping configuration used in Naon Embedded Linux Kit.

RAM Memory Map

Before start reading memory map in detail, please take a look at generic EZSDK Memory Map on Texas Instruments Wiki.

RAM memory map is the most complex part of this architecture, because the user should allocate the different area used by Cortex-A8 processor (which runs the Linux OS), the two media controllers (Cortex-M3, that take care of the whole video processing subsystem) and DSP.

This memory map is statically defined in various places, so the user has a limited options in changing this. Anyway it's useful to know how this memory is shared between the various processors to develop correctly the end-user multimedia application and to know exactly how much memory a processor can use.

Please download the NAON-Memory-Map.ods spreadsheet to view the memory map. The region are named exactly as in EZSDK Memory Map

Memory map spreadsheet also include non-volatile memory mapping: it also ease resize operation of those memories

Non-Volatile Memory Map

Due the fact that different memory size are available on request on Naon SOM, we will review here only the default memory size. Anyway, the beginning of each memory is the same for all of them due boot system restrictions.

Each section correspond to a Linux MTD partition. User can change partition at runtime or by statically by changing Kernel sources. See Memory Tecnology Device (MTD) for more detail regarding this topic.

SPI NOR Flash

SPI NOR Flash is the main boot memory, where available, for Naon module. Due the fact that SPI NOR is a non-XIP memory, Naon uses two-stage U-Boot for booting.

Here is the layout of the default 8MiB memory:

Base Address (HEX)	Size (KiB)	Size (HEX)	Usage
0	128	20000	U-boot 1st stage
20000	256	40000	U-boot 2nd stage
60000	64	10000	U-boot env1
70000	64	10000	U-boot env2
80000	4096	400000	Linux Kernel
480000	28160	1B80000	FREE

The last section is Free for use by the user (e.g. for a ramdisk, a redundant Kernel image or generic storage).

Redundant environment for SPI NOR flash not yet available

NAND Flash

Nand Flash is the main storage memory, even if can be used for boot too. By default Naon is provided with 1GiB Nand but other memory size is available on request. The default Nand partitioning is detailed in the following table:

Base Address (HEX)	Size (MiB)	Size (HEX)	Usage
0	0,125	20000	U-boot 1st stage
20000	0,25	40000	U-boot 2nd stage
60000	0,125	20000	U-Boot env1
50000	0,125	20000	U-boot env2
A0000	4	400000	Linux Kernel
4A0000	123,375	7B60000	File System (small)
8000000	896	38000000	File System (big)

Kernel Command Line parameters

Some parameters should be passed to the Linux kernel via command line. Here is a brief explanation of them and their an example of use (taken from the current default memory map):

• mem=xxxM set the maximum memory given to Linux kernel. In this way the kernel does not use all the memory found and leave memory for Cortex-M3. E.g. mem=176M. In the Naon Memory Map is called LINUX_MEM_1.
• vram=xxxM set the size of memory reserved for video ram (framebuffers). E.g vram=46M. See the Change FB size section below.
• notifyk.vpssm3_sva=address address of notify memory for HDVPSS. E.g notifyk.vpssm3_sva=0xBF900000In the Naon Memory Map is called HDVPSS_NOTIFY_MEM

Always refer to the Naon Memory Map for the correct value to use.

User Options

Without rebuilding Media Controller Firmware (which needs NDA from TI or DAVE Embedded Systems support) user can change some memory map parameter on the fly.

Change FB size

Current NELK support up to 3 Frame Buffers. See Frame Buffer Management -Naon- for more information regarding NELK Frame Buffers.

User can choose how much of Linux kernel memory give to the frame buffer driver and how to divide this memory into the 3 available frame buffer.

The amount of memory that the kernel reserve to the FB is given by the vram command line parameter. For more information in how to change kernel command like parameter see Change Linux Command Line Parameter from U-boot

The amount of memory given away to each frame buffer is described by vram ti81xxfb's module parameter.

E.g. to use 46MiB of RAM for 3 frame buffer, divided in 24MiB for fb0, 16MiB for fb1 and 6MiB for fb2, use:

• vram=46M as command line parameter
• modprobe ti81xxfb vram=0:24M,1:16M,2:6M command to load fb module

User that needs more Linux user space memory and needs only one frame buffer, can, for example, use 6MiB of RAM used only by the first FB, so:

• vram=6M as command line parameter
• modprobe ti81xxfb vram=0:6M command to load fb module

Please note that ti81xxfb is usually loaded at startup from /etc/init.d/load-hd-firmware.sh: user that would like to change the default configuration should change this file.