Documentation/devicetree/bindings/mmc/mmc.txt

   1 These properties are common to multiple MMC host controllers. Any host
   2 that requires the respective functionality should implement them using
   3 these definitions.
   4
   5 Interpreted by the OF core:
   6 - reg: Registers location and length.
   7 - interrupts: Interrupts used by the MMC controller.
   8
   9 Card detection:
  10 If no property below is supplied, host native card detect is used.
  11 Only one of the properties in this section should be supplied:
  12   - broken-cd: There is no card detection available; polling must be used.
  13   - cd-gpios: Specify GPIOs for card detection, see gpio binding
  14   - non-removable: non-removable slot (like eMMC); assume always present.
  15
  16 Optional properties:
  17 - bus-width: Number of data lines, can be <1>, <4>, or <8>.  The default
  18   will be <1> if the property is absent.
  19 - wp-gpios: Specify GPIOs for write protection, see gpio binding
  20 - cd-inverted: when present, polarity on the CD line is inverted. See the note
  21   below for the case, when a GPIO is used for the CD line
  22 - wp-inverted: when present, polarity on the WP line is inverted. See the note
  23   below for the case, when a GPIO is used for the WP line
  24 - max-frequency: maximum operating clock frequency
  25 - no-1-8-v: when present, denotes that 1.8v card voltage is not supported on
  26   this system, even if the controller claims it is.
  27 - cap-sd-highspeed: SD high-speed timing is supported
  28 - cap-mmc-highspeed: MMC high-speed timing is supported
  29 - cap-power-off-card: powering off the card is safe
  30 - cap-sdio-irq: enable SDIO IRQ signalling on this interface
  31
  32 *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
  33 polarity properties, we have to fix the meaning of the "normal" and "inverted"
  34 line levels. We choose to follow the SDHCI standard, which specifies both those
  35 lines as "active low." Therefore, using the "cd-inverted" property means, that
  36 the CD line is active high, i.e. it is high, when a card is inserted. Similar
  37 logic applies to the "wp-inverted" property.
  38
  39 CD and WP lines can be implemented on the hardware in one of two ways: as GPIOs,
  40 specified in cd-gpios and wp-gpios properties, or as dedicated pins. Polarity of
  41 dedicated pins can be specified, using *-inverted properties. GPIO polarity can
  42 also be specified using the OF_GPIO_ACTIVE_LOW flag. This creates an ambiguity
  43 in the latter case. We choose to use the XOR logic for GPIO CD and WP lines.
  44 This means, the two properties are "superimposed," for example leaving the
  45 OF_GPIO_ACTIVE_LOW flag clear and specifying the respective *-inverted
  46 property results in a double-inversion and actually means the "normal" line
  47 polarity is in effect.
  48
  49 Optional SDIO properties:
  50 - keep-power-in-suspend: Preserves card power during a suspend/resume cycle
  51 - enable-sdio-wakeup: Enables wake up of host system on SDIO IRQ assertion
  52
  53 Example:
  54
  55 sdhci@ab000000 {
  56         compatible = "sdhci";
  57         reg = <0xab000000 0x200>;
  58         interrupts = <23>;
  59         bus-width = <4>;
  60         cd-gpios = <&gpio 69 0>;
  61         cd-inverted;
  62         wp-gpios = <&gpio 70 0>;
  63         max-frequency = <50000000>;
  64         keep-power-in-suspend;
  65         enable-sdio-wakeup;
  66 }