1. Article purpose[edit source]
This article explains how to configure the FMC internal peripheral when it is assigned to the Linux® OS. In that case, the FMC NAND Flash controller is controlled by the MTD framework.
The configuration is performed using the device tree mechanism that provides a hardware description of the FMC peripheral, used by the STM32 FMC Linux drivers and by the MTD framework.
2. DT bindings documentation[edit source]
The FMC device tree bindings are composed of:
- generic MTD NAND bindings [1].
- FMC NAND Flash controller driver bindings [2].
- FMC external bus interface driver bindings [3].
3. DT configuration[edit source]
This hardware description is a combination of the STM32 microprocessor device tree files (.dtsi extension) and board device tree files (.dts extension). See the Device tree for an explanation of the device tree file split.
STM32CubeMX can be used to generate the board device tree. Refer to How to configure the DT using STM32CubeMX for more details.
3.1. DT configuration (STM32 level)[edit source]
The FMC peripheral node is located in stm32mp151.dtsi[4] file.
fmc: memory-controller@58002000 { Comments
#address-cells = <2>;
#size-cells = <1>;
compatible = "st,stm32mp1-fmc2-ebi";
reg = <0x58002000 0x1000>; --> This region contains the register location
clocks = <&rcc FMC_K>;
resets = <&rcc FMC_R>;
status = "disabled";
ranges = <0 0 0x60000000 0x04000000>, /* EBI CS 1 */ --> External bus interface region is used to address up to four external devices
<1 0 0x64000000 0x04000000>, /* EBI CS 2 */
<2 0 0x68000000 0x04000000>, /* EBI CS 3 */
<3 0 0x6c000000 0x04000000>, /* EBI CS 4 */
<4 0 0x80000000 0x10000000>; /* NAND */ --> NAND Flash controller region is used to address NAND Flash memory devices
nand-controller@4,0 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "st,stm32mp1-fmc2-nfc";
reg = <4 0x00000000 0x1000>, --> Regions 1 to 3 respectively contain the data, command and address space for CS0
<4 0x08010000 0x1000>,
<4 0x08020000 0x1000>,
<4 0x01000000 0x1000>, --> Regions 4 to 6 contain the same areas for CS1
<4 0x09010000 0x1000>,
<4 0x09020000 0x1000>;
interrupts = <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>; --> The interrupt number used
dmas = <&mdma1 20 0x2 0x12000a02 0x0 0x0 0x0>, --> DMA specifiers [5]
<&mdma1 20 0x2 0x12000a08 0x0 0x0 0x0>,
<&mdma1 21 0x2 0x12000a0a 0x0 0x0 0x0>;
dma-names = "tx", "rx", "ecc";
status = "disabled";
};
};
3.2. DT configuration of the external bus interface controller (board level)[edit source]
The FMC external bus interface controller may connect up to four external devices.
&fmc { Comments
pinctrl-names = "default", "sleep"; --> For pinctrl configuration, please refer to Pinctrl device tree configuration
pinctrl-0 = <&fmc2_pins_b>;
pinctrl-1 = <&fmc2_sleep_pins_b>;
status = "okay"; --> Enable the node
ksz8851: ks8851mll@1,0 {
compatible = "micrel,ks8851-mll"; --> Configure the external device
reg = <1 0x0 0x2>, <1 0x2 0x20000>;
interrupt-parent = <&gpioc>;
interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
bank-width = <2>;
st,fmc2-ebi-cs-mux-enable; --> Configure the transactions with the external device
st,fmc2-ebi-cs-transaction-type = <4>;
st,fmc2-ebi-cs-buswidth = <16>;
st,fmc2-ebi-cs-address-setup-ns = <5>;
st,fmc2-ebi-cs-address-hold-ns = <5>;
st,fmc2-ebi-cs-bus-turnaround-ns = <5>;
st,fmc2-ebi-cs-data-setup-ns = <45>;
st,fmc2-ebi-cs-data-hold-ns = <1>;
};
};
3.3. DT configuration of the NAND Flash controller (board level)[edit source]
The FMC NAND Flash controller may connect to one SLC NAND Flash memory (with a maximum of 2 dies per package).
&fmc { Comments
pinctrl-names = "default", "sleep"; --> For pinctrl configuration, please refer to Pinctrl device tree configuration
pinctrl-0 = <&fmc2_pins_a>;
pinctrl-1 = <&fmc2_sleep_pins_a>;
status = "okay"; --> Enable the node
nand-controller@4,0 {
status = "okay"; --> Enable the NAND controller node
nand@0 {
reg = <0>; --> Describe the CS line assigned to the NAND chip
nand-on-flash-bbt; --> Store the bad block table on NAND Flash memory
nand-ecc-strength = <8>; --> Number of bits to correct per ECC step
nand-ecc-step-size = <512>; --> Number of data bytes that are covered by a single ECC step
#address-cells = <1>;
#size-cells = <1>;
};
};
};
The supported ECC strength and step size are:
- nand-ecc-strength = <1>, nand-ecc-step-size = <512> (HAMMING).
- nand-ecc-strength = <4>, nand-ecc-step-size = <512> (BCH4).
- nand-ecc-strength = <8>, nand-ecc-step-size = <512> (BCH8).
3.4. DT configuration examples[edit source]
The below example shows how to configure the FMC NAND Flash controller when a SLC 8-bit NAND Flash memory device is connected (ECC requirement: 8 bits / 512 bytes).
&fmc {
pinctrl-names = "default", "sleep";
pinctrl-0 = <&fmc2_pins_a>;
pinctrl-1 = <&fmc2_sleep_pins_a>;
status = "okay";
nand-controller@4,0 {
status = "okay";
nand: nand@0 {
reg = <0>;
nand-on-flash-bbt;
#address-cells = <1>;
#size-cells = <1>;
partition@0 {
...
};
};
};
};
The below example shows how to configure the FMC NAND Flash controller when a SLC 8-bit NAND Flash memory device is connected (ECC requirement: 4 bits / 512 bytes).
&fmc {
pinctrl-names = "default", "sleep";
pinctrl-0 = <&fmc2_pins_a>;
pinctrl-1 = <&fmc2_sleep_pins_a>;
status = "okay";
nand-controller@4,0 {
status = "okay";
nand: nand@0 {
reg = <0>;
nand-on-flash-bbt;
nand-ecc-strength = <4>;
nand-ecc-step-size = <512>;
#address-cells = <1>;
#size-cells = <1>;
partition@0 {
...
};
};
};
};
4. How to configure the DT using STM32CubeMX[edit source]
The STM32CubeMX tool can be used to configure the STM32MPU device and get the corresponding platform configuration device tree files.
The STM32CubeMX may not support all the properties described in the above DT bindings documentation paragraph. If so, the tool inserts user sections in the generated device tree. These sections can then be edited to add some properties and they are preserved from one generation to another. Refer to STM32CubeMX user manual for further information.
5. References[edit source]
Please refer to the following links for full description: