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overlays: sdhost: Add gpios_22_27 and bus_width parameters #7467

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overlays: sdhost: Add gpios_22_27 and bus_width parameters #7467

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7 changes: 7 additions & 0 deletions arch/arm/boot/dts/overlays/README
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Original file line number Diff line number Diff line change
Expand Up @@ -4737,6 +4737,13 @@ Params: overclock_50 Clock (in MHz) to use when the MMC framework

debug Enable debug output (default off)

bus_width MMC bus width (default 1)

@pelwell pelwell Jul 2, 2026

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The default bus-width is theoretically platform-dependent, but in practice it is always going to be 4.


gpios_22_27 Route SD0 to GPIO 22-27 (CLK, CMD, DAT0-3)
for use with a secondary SD card slot on
custom carrier boards (e.g. CM4 baseboard).
Applies ALT0 function and appropriate pulls.


Name: sdio
Info: Selects the bcm2835-sdhost SD/MMC driver, optionally with overclock,
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21 changes: 21 additions & 0 deletions arch/arm/boot/dts/overlays/sdhost-overlay.dts
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Expand Up @@ -29,10 +29,31 @@
};
};

fragment@3 {
target = <&gpio>;
__dormant__ {
sdhost_gpio_22_27: sdhost_gpio_22_27 {
brcm,pins = <22 23 24 25 26 27>;
brcm,function = <4>;
brcm,pull = <0 2 2 2 2 2>;
};
};
};

fragment@4 {
target = <&sdhost>;
__dormant__ {
pinctrl-names = "default";
pinctrl-0 = <&sdhost_gpio_22_27>;
};
};

__overrides__ {
overclock_50 = <&frag0>,"brcm,overclock-50:0";
force_pio = <&frag0>,"brcm,force-pio?";
pio_limit = <&frag0>,"brcm,pio-limit:0";
debug = <&frag0>,"brcm,debug?";
bus_width = <&frag0>,"bus-width:0";
gpios_22_27 = <0>,"+3+4";
};
};
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