diff options
Diffstat (limited to '')
| -rw-r--r-- | Documentation/devicetree/bindings/mmc/mmc.txt | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt new file mode 100644 index 000000000..c269dbe38 --- /dev/null +++ b/Documentation/devicetree/bindings/mmc/mmc.txt @@ -0,0 +1,177 @@ +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 +- cd-debounce-delay-ms: Set delay time before detecting card after card insert interrupt. + It's only valid when cd-gpios is present. +- 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 +- disable-wp: When set no physical WP line is present. This property should + only be specified when the controller has a dedicated write-protect + detection logic. If a GPIO is always used for the write-protect detection + logic it is sufficient to not specify wp-gpios property in the absence of a 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-mmc-hw-reset: eMMC hardware reset is supported +- cap-sdio-irq: enable SDIO IRQ signalling on this interface +- full-pwr-cycle: full power cycle of the card is supported +- mmc-ddr-3_3v: eMMC high-speed DDR mode(3.3V I/O) is supported +- mmc-ddr-1_8v: eMMC high-speed DDR mode(1.8V I/O) is supported +- mmc-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 +- mmc-hs400-1_8v: eMMC HS400 mode(1.8V I/O) is supported +- mmc-hs400-1_2v: eMMC HS400 mode(1.2V I/O) is supported +- mmc-hs400-enhanced-strobe: eMMC HS400 enhanced strobe mode is supported +- dsr: Value the card's (optional) Driver Stage Register (DSR) should be + programmed with. Valid range: [0 .. 0xffff]. +- no-sdio: controller is limited to send sdio cmd during initialization +- no-sd: controller is limited to send sd cmd during initialization +- no-mmc: controller is limited to send mmc cmd during initialization +- fixed-emmc-driver-type: for non-removable eMMC, enforce this driver type. + The value <n> is the driver type as specified in the eMMC specification + (table 206 in spec version 5.1). +- post-power-on-delay-ms : It was invented for MMC pwrseq-simple which could + be referred to mmc-pwrseq-simple.txt. But now it's reused as a tunable delay + waiting for I/O signalling and card power supply to be stable, regardless of + whether pwrseq-simple is used. Default to 10ms if no available. +- supports-cqe : The presence of this property indicates that the corresponding + MMC host controller supports HW command queue feature. +- disable-cqe-dcmd: This property indicates that the MMC controller's command + queue engine (CQE) does not support direct commands (DCMDs). + +*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 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 +GPIO_ACTIVE_LOW flag clear and specifying the respective *-inverted property +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 +- wakeup-source: Enables wake up of host system on SDIO IRQ assertion + (Legacy property supported: "enable-sdio-wakeup") + +MMC power +--------- + +Controllers may implement power control from both the connected cards and +the IO signaling (for example to change to high-speed 1.8V signalling). If +the system supports this, then the following two properties should point +to valid regulator nodes: + +- vqmmc-supply: supply node for IO line power +- vmmc-supply: supply node for card's power + + +MMC power sequences: +-------------------- + +System on chip designs may specify a specific MMC power sequence. To +successfully detect an (e)MMC/SD/SDIO card, that power sequence must be +maintained while initializing the card. + +Optional property: +- mmc-pwrseq: phandle to the MMC power sequence node. See "mmc-pwrseq-*" + for documentation of MMC power sequence bindings. + + +Use of Function subnodes +------------------------ + +On embedded systems the cards connected to a host may need additional +properties. These can be specified in subnodes to the host controller node. +The subnodes are identified by the standard 'reg' property. +Which information exactly can be specified depends on the bindings for the +SDIO function driver for the subnode, as specified by the compatible string. + +Required host node properties when using function subnodes: +- #address-cells: should be one. The cell is the slot id. +- #size-cells: should be zero. + +Required function subnode properties: +- reg: Must contain the SDIO function number of the function this subnode + describes. A value of 0 denotes the memory SD function, values from + 1 to 7 denote the SDIO functions. + +Optional function subnode properties: +- compatible: name of SDIO function following generic names recommended practice + + +Examples +-------- + +Basic 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; + wakeup-source; + mmc-pwrseq = <&sdhci0_pwrseq> +} + +Example with sdio function subnode: + +mmc3: mmc@1c12000 { + #address-cells = <1>; + #size-cells = <0>; + + pinctrl-names = "default"; + pinctrl-0 = <&mmc3_pins_a>; + vmmc-supply = <®_vmmc3>; + bus-width = <4>; + non-removable; + mmc-pwrseq = <&sdhci0_pwrseq> + + brcmf: bcrmf@1 { + reg = <1>; + compatible = "brcm,bcm43xx-fmac"; + interrupt-parent = <&pio>; + interrupts = <10 8>; /* PH10 / EINT10 */ + interrupt-names = "host-wake"; + }; +}; |