SDMMC device tree configuration
目录
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 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";
};
 |
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
有关更多信息，请参阅以下链接：
- ↑ 1.01.1 Documentation/devicetree/bindings/mmc/mmc.txt| |}} Documentation/devicetree/bindings/mmc/mmc.txt
- ↑ Documentation/devicetree/bindings/mmc/mmci.txt| |}} Documentation/devicetree/bindings/mmc/mmci.txt
- ↑ arch/arm/boot/dts/stm32mp157c.dtsi| |}} arch/arm/boot/dts/stm32mp157c.dtsi
- ↑ 4.04.1 arch/arm/boot/dts/stm32mp157c-ed1.dts| |}} arch/arm/boot/dts/stm32mp157c-ed1.dts
