SPI-Nor Flash

The Kumquat board includes an 8MB SPI-Nor Flash memory chip, the Winbond W25Q64JVSIQ. This memory is used to store critical components like the bootloader (U-Boot) and its environment variables, along with providing additional storage for user data. The flash memory is managed using mtdparts and divided into several partitions.

Information

The SPI-Nor Flash contains the following partitions:

Bootloader (U-Boot): A read-only partition for the bootloader.
U-Boot Environment (env1 and env2): Two redundant partitions for U-Boot configuration.
User Partition: A partition available for storing user data.

The current configuration is as follows:

mtdparts=firmware:512k(u-boot)ro,256k(u-boot-env1),256k(u-boot-env2),-(user)

This setup assigns 512KB to U-Boot, 256KB each for U-Boot environment 1 and 2, and the remainder to the user partition.

Checking if the SPI-Nor Flash is Detected

To verify the presence of the SPI-Nor Flash, you can list the MTD devices using the following command:

cat /proc/mtd

The expected output should resemble the following:

mtd0: 00080000 00010000 "u-boot"
mtd1: 00040000 00010000 "u-boot-env1"
mtd2: 00040000 00010000 "u-boot-env2"
mtd3: 00700000 00010000 "user"

The user partition (mtd3 in this case) is where user data can be stored.

Writing to the SPI-Nor Flash

To write data to the user partition of the SPI-Nor Flash, you can use standard Linux tools like dd for writing raw data to the MTD block device.

Here is an example of how to write a file to the user partition:

Prepare the file you want to store in the Flash.
Use dd to copy the file to the user partition:

dd if=mydata.bin of=/dev/mtd3 bs=4096

This writes the contents of mydata.bin to the user partition (mtd3), using a block size of 4096 bytes.

Reading from the SPI-Nor Flash

To read data from the user partition, you can use dd to copy the contents to a file:

dd if=/dev/mtd3 of=readback.bin bs=4096

This command copies the content of the user partition to readback.bin. You can then inspect or process this file as needed.

Alternatively, you can display the content directly in the terminal:

cat /dev/mtd3

This command will print the raw contents of the user partition to the terminal.

Summary of the Flash Layout

MTD Block	Size	Description
mtd0	512KB	U-Boot
mtd1	256KB	U-Boot Environment 1
mtd2	256KB	U-Boot Environment 2
mtd3	~6MB	User Partition

The SPI-Nor Flash on the Kumquat board is divided into fixed partitions, with the user partition available for data storage. By using standard Linux commands, you can write and read data to and from the SPI-Nor Flash without needing external tools like flashcp.

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