SDMMC device tree configuration

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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 [1].
  • SDMMC MMC/SD/SDIO接口绑定 [2].

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[3]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";
   };
Warning.png 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。[4].

   &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) [4].

   &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 [1]
       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工具可用于配置STM32MPU设备并获取相应的platform configuration device tree 文件。
STM32CubeMX可能不支持以上 DT bindings documentation 段中描述的所有属性。 如果是这样,该工具会在生成的设备树中插入“用户部分”。 然后可以编辑这些部分以添加一些属性,并将它们一代一代地保留下来。 有关更多信息,请参见STM32CubeMX 用户手册。

References

Please refer to the following links for additional information:

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