The latest development version of this page may be more current than this released 3.7.0 version.

st,stm32-fmc-sdram

Vendor: STMicroelectronics

Description

STM32 Flexible Memory Controller (SDRAM controller).

The FMC SDRAM controller can be used to interface with external SDRAM
memories. Up to 2 SDRAM banks are supported with independent configuration. It
is worth to note that while settings are independent, some are shared or are
required to be set according to the most constraining device. Refer to the
properties description or the datasheet for more details.

The FMC SDRAM controller is defined below the FMC node and SDRAM banks are
defined as child nodes of the FMC SDRAM node. You can either have bank 1 (@0),
bank 2 (@1) or both. You can enable the FMC SDRAM controller in your board
DeviceTree file like this:

&fmc {
    status = "okay";
    pinctrl-0 = <&fmc_nbl0_pe0 &fmc_nbl1_pe1 &fmc_nbl2_pi4...>;

    sdram {
        status = "okay";

        power-up-delay = <100>;
        num-auto-refresh = <8>;
        mode-register = <0x220>;
        refresh-rate = <603>;

        bank@0 {
            reg = <0>;

            st,sdram-control = <STM32_FMC_SDRAM_NC_9
                                STM32_FMC_SDRAM_NR_12
                                STM32_FMC_SDRAM_MWID_32
                                STM32_FMC_SDRAM_NB_4
                                STM32_FMC_SDRAM_CAS_2
                                STM32_FMC_SDRAM_SDCLK_PERIOD_2
                                STM32_FMC_SDRAM_RBURST_ENABLE
                                STM32_FMC_SDRAM_RPIPE_0>;
            st,sdram-timing = <2 6 4 6 2 2 2>;
        };

        bank@1 {
            reg = <1>;
            ...
        };
    };
};

Note that you will find definitions for the st,sdram-control field at
dt-bindings/memory-controller/stm32-fmc-sdram.h. This file is already included
in the SoC DeviceTree files.

Finally, in order to make the memory available you will need to define new
memory device/s in DeviceTree:

sdram1: sdram@c0000000 {
    compatible = "zephyr,memory-region", "mmio-sram";
    device_type = "memory";
    reg = <0xc000000 DT_SIZE_M(X)>;
    zephyr,memory-region = "SDRAM1";
};

sdram2: sdram@d0000000 {
    compatible = "zephyr,memory-region", "mmio-sram";
    device_type = "memory";
    reg = <0xd000000 DT_SIZE_M(X)>;
    zephyr,memory-region = "SDRAM2";
};

It is important to use sdram1 and sdram2 node labels for bank 1 and bank 2
respectively. Memory addresses are 0xc0000000 and 0xd0000000 for bank 1 and
bank 2 respectively.

Properties

Top level properties

These property descriptions apply to “st,stm32-fmc-sdram” nodes themselves. This page also describes child node properties in the following sections.

Node specific propertiesDeprecated node specific propertiesBase properties

Properties not inherited from the base binding file.

Name	Type	Details
power-up-delay	int	Power-up delay in microseconds. Default value: 100
num-auto-refresh	int	Number of auto-refresh commands issued. Default value: 8
mode-register	int	A 14-bit field that defines the SDRAM Mode Register content. The mode register bits are also used to program the extended mode register for mobile SDRAM. This property is required.
refresh-rate	int	A 13-bit field defines the refresh rate of the SDRAM device. It is expressed in number of memory clock cycles. It must be set at least to 41 SDRAM clock cycles. This property is required.

Child node properties

Name	Type	Details
reg	int	This property is required. See Important properties for more information.
st,sdram-control	array	SDRAM control configuration. Expected fields, in order, are, - NC: Number of bits of a column address. - NR: Number of bits of a row address. - MWID: Memory device width. - NB: Number of internal banks. - CAS: SDRAM CAS latency in number of memory clock cycles. - SDCLK: SDRAM clock period. If two SDRAM devices are used both should have the same value. - RBURST: Enable burst read mode. If two SDRAM devices are used both should have the same value. - RPIPE: Delay, in fmc_ker_ck clock cycles, for reading data after CAS latency. If two SDRAM devices are used both should have the same value. This property is required.
st,sdram-timing	array	SDRAM timing configuration. Expected fields, in order, are, - TMRD: Delay between a Load Mode Register command and an Active or Refresh command in number of memory clock cycles. - TXSR: Delay from releasing the Self-refresh command to issuing the Activate command in number of memory clock cycles. If two SDRAM devices are used, the FMC_SDTR1 and FMC_SDTR2 must be programmed with the same TXSR timing corresponding to the slowest SDRAM device - TRAS: Minimum Self-refresh period in number of memory clock cycles. - TRC: Delay between the Refresh command and the Activate command, as well as the delay between two consecutive Refresh commands. It is expressed in number of memory clock cycles. If two SDRAM devices are used, the TRC must be programmed with the timings of the slowest device in both banks. - TWP: Delay between a Write and a Precharge command in number of memory clock cycles - TRP: Delay between a Precharge command and another command in number of memory clock cycles. If two SDRAM devices are used, the TRP must be programmed with the timing of the slowest device in both banks. - TRCD: Delay between the Activate command and a Read/Write command in number of memory clock cycles. This property is required.