[RFC v2 1/2] dt-bindings: mmc: Document the Amlogic Meson8 and Meson8b SDIO bindings

[Martin Blumenstingl]

On Mon, Oct 2, 2017 at 9:55 AM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> On 24 September 2017 at 21:05, Martin Blumenstingl
> <martin.blumenstingl at googlemail.com> wrote:
>> From: Carlo Caione <carlo at endlessm.com>
>>
>> This documents the devicetree bindings for the SDIO/MMC host found in
>> Amlogic Meson8 and Meson8b SoCs. It supports the SD specification v2.0
>> and the eMMC specification v4.41.
>> It has an internal "mux" which allows connecting up to three MMC devices
>> to it. The maximum supported bus-width is 4-bits.
>>
>> Amlogic's GPL kernel sources call it "SDIO" to differentiate it from the
>> other MMC controller in (at least the Meson8 and Meson8b) the SoCs (they
>> call the other one "SDHC", which supports a bus-width of up to 8-bits).
>>
>> Signed-off-by: Carlo Caione <carlo at endlessm.com>
>> Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
>> ---
>>  .../bindings/mmc/amlogic,meson-mx-sdio.txt         | 52 ++++++++++++++++++++++
>>  1 file changed, 52 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt b/Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt
>> new file mode 100644
>> index 000000000000..124ea362eec9
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdio.txt
>> @@ -0,0 +1,52 @@
>> +* Amlogic Meson6, Meson8 and Meson8b SDIO/MMC controller
>> +
>> +The highspeed MMC host controller on Amlogic SoCs provides an interface
>> +for MMC, SD, SDIO and SDHC types of memory cards.
>> +
>> +Supported maximum speeds are the ones of the eMMC standard 4.41 as well
>> +as the speed of SD standard 2.0.
>> +
>> +The hardware provides an internal "mux" which allows up to three slots
>> +to be controlled. Only one slot can be accessed at a time.
>
> This is good information, however as the driver won't support multiple
> slots, at least short term, I think we need to mention that. Otherwise
> people may think that three slots is actually supported, while in fact
> it isn't.
OK, I'll add a note when I re-spin this series

>> +
>> +Required properties:
>> + - compatible : must be one of
>> +       - "amlogic,meson8-sdio"
>> +       - "amlogic,meson8b-sdio"
>> +       along with the generic "amlogic,meson-mx-sdio"
>> + - reg : mmc controller base registers
>> + - interrupts : mmc controller interrupt
>> + - #address-cells : must be 1
>> + - size-cells : must be 0
>> + - clocks : phandle to clock providers
>> + - clock-names : must contain "core" and "clkin"
>> +
>> +Required child nodes:
>> +A node for each slot provided by the MMC controller is required.
>> +
>> +Required properties on each child node (= slot):
>> + - compatible : must be "mmc-slot" (see mmc.txt within this directory)
>> + - reg : the slot (or "port") ID
>> +
>> +Optional properties on each child node (= slot):
>> + - bus-width : must be 1 or 4 (8-bit bus is not supported)
>> + - for cd and all other additional generic mmc parameters
>> +   please refer to mmc.txt within this directory
>> +
>> +Examples:
>> +       mmc at c1108c20 {
>> +               compatible = "amlogic,meson8-sdio", "amlogic,meson-mx-sdio";
>> +               reg = <0xc1108c20 0x20>;
>> +               interrupts = <0 28 1>;
>> +               #address-cells = <1>;
>> +               #size-cells = <0>;
>> +               clocks = <&clkc CLKID_SDIO>, <&clkc CLKID_CLK81>;
>> +               clock-names = "core", "clkin";
>> +
>> +               slot at 1 {
>> +                       compatible = "mmc-slot";
>> +                       reg = <1>;
>> +
>> +                       bus-width = <4>;
>> +               };
>> +       };
>> --
>> 2.14.1
>>
>
> Kind regards
> Uffe


Regards,
Martin