[PATCH 1/3] powerpc: Add mmc-spi-slot bindings
Grant Likely
grant.likely at secretlab.ca
Fri Oct 31 07:37:31 EST 2008
On Thu, Oct 30, 2008 at 1:56 PM, Anton Vorontsov
<avorontsov at ru.mvista.com> wrote:
> The bindings describes a case where MMC/SD/SDIO slot directly connected
> to a SPI bus. Such setups are widely used on embedded PowerPC boards.
>
> The patch also adds the mmc-spi-slot entry to the OpenFirmware modalias
> table.
>
> Signed-off-by: Anton Vorontsov <avorontsov at ru.mvista.com>
Mostly looks good to me. A few comments below.
> ---
> .../powerpc/dts-bindings/mmc-spi-slot.txt | 23 ++++++++++++++++++++
> drivers/of/base.c | 1 +
> 2 files changed, 24 insertions(+), 0 deletions(-)
> create mode 100644 Documentation/powerpc/dts-bindings/mmc-spi-slot.txt
>
> diff --git a/Documentation/powerpc/dts-bindings/mmc-spi-slot.txt b/Documentation/powerpc/dts-bindings/mmc-spi-slot.txt
> new file mode 100644
> index 0000000..c39ac28
> --- /dev/null
> +++ b/Documentation/powerpc/dts-bindings/mmc-spi-slot.txt
> @@ -0,0 +1,23 @@
> +MMC/SD/SDIO slot directly connected to a SPI bus
> +
> +Required properties:
> +- compatible : should be "mmc-spi-slot".
> +- reg : should specify SPI address (chip-select number).
> +- spi-max-frequency : maximum frequency for this device (Hz).
> +- voltage-ranges : two cells are required, first cell specifies minimum
> + slot voltage (mV), second cell specifies maximum slot voltage (mV).
> + Several ranges could be specified.
> +- gpios : (optional) may specify GPIOs in this order: Card-Detect GPIO,
> + Write-Protect GPIO.
I wonder if we're following the example of irq mappings too closely
for the gpios property. I like the layout of the property
(<controller> <specifier>), but I think the 'gpios' name is getting
too overloaded. In this case a single property 'gpios' is being used
to encode 2 unrelated bits of information; the write protect pin and
the card detect pins.
In this particular case I think it is better to use 2 properties in
this case; something like 'spi-writeprotect-gpio' and
'spi-carddetect-gpio' using the same specifier format. Doing so adds
a bit more clarity to the purpose of the properties.
I my mind I differentiate this from other examples (for instance a
series of CS pins) based on how closely related the pin functions are.
So I would say for the following examples...
1) GPIO data bus (SPI, MDIO and I2C are great examples); all pins must
be present - single gpio property
2) This MMC case (pins are optional and unrelated); separate gpio properties
3) LCD with backlight and contrast control pins; one gpio property for
backlight pins, one for constrast pins.
Thoughts?
> +
> +Example:
> +
> + mmc-slot at 0 {
> + compatible = "fsl,mpc8323rdb-mmc-slot",
> + "mmc-spi-slot";
> + reg = <0>;
> + gpios = <&qe_pio_d 14 1
> + &qe_pio_d 15 0>;
> + voltage-ranges = <3300 3300>;
> + spi-max-frequency = <50000000>;
> + };
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 7c79e94..c6797ca 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -411,6 +411,7 @@ struct of_modalias_table {
> };
> static struct of_modalias_table of_modalias_table[] = {
> { "fsl,mcu-mpc8349emitx", "mcu-mpc8349emitx" },
> + { "mmc-spi-slot", "mmc_spi" },
> };
>
> /**
> --
> 1.5.6.3
>
>
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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