SDMMC device tree configuration

Article purpose

本文介绍了将SDMMC internal peripheral分配给 Linux^® OS. 时如何配置。 在这种情况下，它由 MMC framework控制。 使用device tree 机制执行配置，该机制提供STM32 SDMMC Linux驱动程序和MMC框架使用的SDMMC外设的硬件描述。

如果外围设备已分配给另一个执行上下文，请参阅 How to assign an internal peripheral to a runtime context 文章，以获取有关外围设备分配和配置的准则。

DT bindings documentation

SDMMC设备树绑定包括：

• 通用MMC设备树绑定 .

• SDMMC MMC/SD/SDIO接口绑定 .

DT configuration

该硬件描述是STM32微处理器设备树文件（扩展名为.dtsi）和板子设备树文件（扩展名为.dts）的组合。 有关设备树文件分割的说明，请参见Device tree。

STM32CubeMX可用于生成板卡设备树。 有关更多详细信息，请参考How to configure the DT using STM32CubeMX。

DT configuration (STM32 level)

SDMMC外设节点位于``stm32mp157c.dtsi文件。

   sdmmc1: sdmmc@58005000 {                                  Comments
       compatible = "arm,pl18x", "arm,primecell";
       arm,primecell-periphid = <0x00253180>;
       reg = <0x58005000 0x1000>,                            --> The controller register location 
             <0x58006000 0x1000>;                            --> The delay block register location
       interrupts = <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>;        --> The interrupt number used
       interrupt-names = "cmd_irq";
       clocks = <&rcc SDMMC1_K>;
       clock-names = apb_pclk
       resets = <&rcc SDMMC1_R>;                      
       status = "disabled";
   };

该设备树部分与STM32微处理器有关。 它应该保持原样，而不要由最终用户修改。

DT configuration (board level)

SDMMC外围设备可以连接到一张SD卡，一张“ e”•MMC™设备或一张SDIO卡。

   &sdmmc1{                                                  Comments     
       pinctrl-names = "default", "opendrain", "sleep";      --> For pinctrl configuration, please refer to Pinctrl device tree configuration
       pinctrl-0 = <&sdmmc1_b4_pins_a &sdmmc1_dir_pins_a>;
       pinctrl-1 = <&sdmmc1_b4_od_pins_a &sdmmc1_dir_pins_a>;
       pinctrl-2 = <&sdmmc1_b4_sleep_pins_a &sdmmc1_dir_sleep_pins_a>;
       st,neg-edge;                                          --> Generate data and command on sdmmc clock falling edge
       st,sig-dir;                                           --> Allow to select direction polarity of an external transceiver
       st,use-ckin;                                          --> Use sdmmc_ckin pin from an external transceiver to sample the receive data
       bus-width = <4>;                                      --> Number of data lines, can be 1, 4 or 8
       vmmc-supply = <&vdd_sd>;                              --> Supply node for card's power
       vqmmc-supply = <&sd_switch>;                          --> Supply node for IO line power
       status = "okay";                                      --> Enable the node
   };

连接外部收发器时，必须使用以下可选属性：

• st，sig-dir：此属性允许选择外部收发器方向信号的极性。 设置此属性后，方向信号为高电平时，电压收发器IO将作为输出驱动。 如果不设置此属性，则当方向信号为低电平时，电压收发器IO将作为输出驱动。
• st，use-ckin：通过设置此属性，来自外部收发器的sdmmc_ckin引脚用于采样接收数据。

DT configuration examples

下面的示例显示了当一个‘’e‘’·mmc内核连接到8条数据线时如何配置sdmmc。.

   &sdmmc2{                                                  Comments     
       pinctrl-names = "default", "opendrain", "sleep";      
       pinctrl-0 = <&sdmmc2_b4_pins_a &sdmmc2_dir_pins_a>;
       pinctrl-1 = <&sdmmc2_b4_od_pins_a &sdmmc2_dir_pins_a>;
       pinctrl-2 = <&sdmmc2_b4_sleep_pins_a &sdmmc2_dir_sleep_pins_a>;             
       non-removable;                                        --> Non-removable slot, assume always present
       no-sd;                                                --> Avoid to send SD command during initialization
       no-sdio;                                              --> Avoid to send SDIO command during initialization
       st,neg-edge;                                           
       bus-width = <8>;                                    
       vmmc-supply = <&v3v3>;                      
       vqmmc-supply = <&vdd>;
       mmc-ddr-3_3v;                                         --> Host supports e•MMC™ DDR 3.3V                         
       status = "okay";                                     
   };

下例显示了如何使用外部收发器将SDMMC配置为SD卡（4条数据线） .

   &sdmmc1{                                                  Comments     
       pinctrl-names = "default", "opendrain", "sleep";    
       pinctrl-0 = <&sdmmc1_b4_pins_a &sdmmc1_dir_pins_a>;
       pinctrl-1 = <&sdmmc1_b4_od_pins_a &sdmmc1_dir_pins_a>;
       pinctrl-2 = <&sdmmc1_b4_sleep_pins_a &sdmmc1_dir_sleep_pins_a>;               
       broken-cd;                                            --> use polling mode for card detection
       st,neg-edge;
       st,sig-dir;
       st,use-ckin;                                    
       bus-width = <4>;
       sd-uhs-sdr12;                                         --> sd modes supported 
       sd-uhs-sdr25;
       sd-uhs-sdr50;
       sd-uhs-ddr50;
       sd-uhs-sdr104;
       vmmc-supply = <&vdd_sd>;                      
       vqmmc-supply = <&sd_switch>;                          
       status = "okay";                                     
   };

How to configure the DT using STM32CubeMX

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.

References

Please refer to the following links for additional information:

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