Memory organization (Naon)
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
- 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.
|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|
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 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|
|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=xxxMset 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=xxxMset the size of memory reserved for video ram (framebuffers). E.g
vram=46M. See the Change FB size section below.
notifyk.vpssm3_sva=addressaddress 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.
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=46Mas command line parameter
modprobe ti81xxfb vram=0:24M,1:16M,2:6Mcommand 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=6Mas command line parameter
modprobe ti81xxfb vram=0:6Mcommand 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.