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mmc: pwrseq: Document DT bindings for the simple MMC power sequence

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To support SOCs which specifies specific MMC power sequences, document
some MMC DT bindings to be able to describe these hardwares.

Let's also document bindings for a simple MMC power sequence provider,
which purpose is to support a set of common properties between various
SOCs.

In this initial step, let's also document a top level description of
the MMC power sequence and describe the compatible string used for the
simple MMC power sequence provider.

The simple MMC power sequence provider will initially support a reset
GPIO. From several earlier posted patches, it's clear that such
hardware exists. Especially some WLAN chips which are attached to an
SDIO interface may use a GPIO reset.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
This commit is contained in:
Ulf Hansson 2014-12-08 15:26:13 +01:00
parent 3aa8793f75
commit 0e6d633274
2 changed files with 34 additions and 0 deletions
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20
Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.txt Normal file
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@ -0,0 +1,20 @@
* The simple MMC power sequence provider
The purpose of the simple MMC power sequence provider is to supports a set of
common properties between various SOC designs. It thus enables us to use the
same provider for several SOC designs.
Required properties:
- compatible : contains "mmc-pwrseq-simple".
Optional properties:
- reset-gpios : contains a GPIO specifier. The reset GPIO is asserted at
initialization and prior we start the power up procedure of the card. It
will be de-asserted right after the power has been provided to the card.
Example:
sdhci0_pwrseq {
compatible = "mmc-pwrseq-simple";
reset-gpios = <&gpio1 12 0>;
}

14
Documentation/devicetree/bindings/mmc/mmc.txt
View file

@ -65,6 +65,18 @@ Optional SDIO properties:
- enable-sdio-wakeup: Enables wake up of host system on SDIO IRQ assertion
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
------------------------
@ -101,6 +113,7 @@ sdhci@ab000000 {
max-frequency = <50000000>;
keep-power-in-suspend;
enable-sdio-wakeup;
mmc-pwrseq = <&sdhci0_pwrseq>
}
Example with sdio function subnode:
@ -114,6 +127,7 @@ mmc3: mmc@01c12000 {
vmmc-supply = <&reg_vmmc3>;
bus-width = <4>;
non-removable;
mmc-pwrseq = <&sdhci0_pwrseq>
status = "okay";
brcmf: bcrmf@1 {