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Diffstat (limited to 'dts/Bindings/mmc/mmc.txt')
| -rw-r--r-- | dts/Bindings/mmc/mmc.txt | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/dts/Bindings/mmc/mmc.txt b/dts/Bindings/mmc/mmc.txt new file mode 100644 index 0000000000..9dce540771 --- /dev/null +++ b/dts/Bindings/mmc/mmc.txt @@ -0,0 +1,76 @@ +These properties are common to multiple MMC host controllers. Any host +that requires the respective functionality should implement them using +these definitions. + +Interpreted by the OF core: +- reg: Registers location and length. +- interrupts: Interrupts used by the MMC controller. + +Card detection: +If no property below is supplied, host native card detect is used. +Only one of the properties in this section should be supplied: + - broken-cd: There is no card detection available; polling must be used. + - cd-gpios: Specify GPIOs for card detection, see gpio binding + - non-removable: non-removable slot (like eMMC); assume always present. + +Optional properties: +- bus-width: Number of data lines, can be <1>, <4>, or <8>. The default + will be <1> if the property is absent. +- wp-gpios: Specify GPIOs for write protection, see gpio binding +- cd-inverted: when present, polarity on the CD line is inverted. See the note + below for the case, when a GPIO is used for the CD line +- wp-inverted: when present, polarity on the WP line is inverted. See the note + below for the case, when a GPIO is used for the WP line +- max-frequency: maximum operating clock frequency +- no-1-8-v: when present, denotes that 1.8v card voltage is not supported on + this system, even if the controller claims it is. +- cap-sd-highspeed: SD high-speed timing is supported +- cap-mmc-highspeed: MMC high-speed timing is supported +- sd-uhs-sdr12: SD UHS SDR12 speed is supported +- sd-uhs-sdr25: SD UHS SDR25 speed is supported +- sd-uhs-sdr50: SD UHS SDR50 speed is supported +- sd-uhs-sdr104: SD UHS SDR104 speed is supported +- sd-uhs-ddr50: SD UHS DDR50 speed is supported +- cap-power-off-card: powering off the card is safe +- cap-sdio-irq: enable SDIO IRQ signalling on this interface +- full-pwr-cycle: full power cycle of the card is supported +- mmc-highspeed-ddr-1_8v: eMMC high-speed DDR mode(1.8V I/O) is supported +- mmc-highspeed-ddr-1_2v: eMMC high-speed DDR mode(1.2V I/O) is supported +- mmc-hs200-1_8v: eMMC HS200 mode(1.8V I/O) is supported +- mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported + +*NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line +polarity properties, we have to fix the meaning of the "normal" and "inverted" +line levels. We choose to follow the SDHCI standard, which specifies both those +lines as "active low." Therefore, using the "cd-inverted" property means, that +the CD line is active high, i.e. it is high, when a card is inserted. Similar +logic applies to the "wp-inverted" property. + +CD and WP lines can be implemented on the hardware in one of two ways: as GPIOs, +specified in cd-gpios and wp-gpios properties, or as dedicated pins. Polarity of +dedicated pins can be specified, using *-inverted properties. GPIO polarity can +also be specified using the OF_GPIO_ACTIVE_LOW flag. This creates an ambiguity +in the latter case. We choose to use the XOR logic for GPIO CD and WP lines. +This means, the two properties are "superimposed," for example leaving the +OF_GPIO_ACTIVE_LOW flag clear and specifying the respective *-inverted +property results in a double-inversion and actually means the "normal" line +polarity is in effect. + +Optional SDIO properties: +- keep-power-in-suspend: Preserves card power during a suspend/resume cycle +- enable-sdio-wakeup: Enables wake up of host system on SDIO IRQ assertion + +Example: + +sdhci@ab000000 { + compatible = "sdhci"; + reg = <0xab000000 0x200>; + interrupts = <23>; + bus-width = <4>; + cd-gpios = <&gpio 69 0>; + cd-inverted; + wp-gpios = <&gpio 70 0>; + max-frequency = <50000000>; + keep-power-in-suspend; + enable-sdio-wakeup; +} |