Re: [RFC] dt: bindings: add bindings for Broadcom bcm43xx sdio devices

[Arend van Spriel <arend-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>]

On 02/13/2014 10:13 AM, Tomasz Figa wrote:
> Hi Arend,
> 
> On 10.02.2014 20:17, Arend van Spriel wrote:
>> The Broadcom bcm43xx sdio devices are fullmac devices that may be
>> integrated in ARM platforms. Currently, the brcmfmac driver for
>> these devices support use of platform data. This patch specifies
>> the bindings that allow this platform data to be expressed in the
>> devicetree.
>>
>> Cc: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>
>> Cc: Tomasz Figa <tomasz.figa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> Reviewed-by: Hante Meuleman <meuleman-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
>> Reviewed-by: Pieter-Paul Giesberts <pieterpg-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
>> Signed-off-by: Arend van Spriel <arend-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
>> ---
>> This devicetree binding proposal is intended for platforms with
>> Broadcom wireless device in MMC sdio slot. These devices may
>> have their own interrupt and power line. Also the SDIO drive
>> strength is often hardware dependent and expressed in this
>> binding.
>>
>> Not sure if this should go in staging or not. Feel free to
>> comment on this proposal.
>>
>> Regards,
>> Arend
>> ---
>>   .../staging/net/wireless/brcm,bcm43xx-fmac.txt     |   37
>> ++++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>   create mode 100644
>> Documentation/devicetree/bindings/staging/net/wireless/brcm,bcm43xx-fmac.txt
>>
>>
>> diff --git
>> a/Documentation/devicetree/bindings/staging/net/wireless/brcm,bcm43xx-fmac.txt
>> b/Documentation/devicetree/bindings/staging/net/wireless/brcm,bcm43xx-fmac.txt
>>
>> new file mode 100644
>> index 0000000..535f343
>> --- /dev/null
>> +++
>> b/Documentation/devicetree/bindings/staging/net/wireless/brcm,bcm43xx-fmac.txt
>>
>> @@ -0,0 +1,37 @@
>> +Broadcom BCM43xx Fullmac wireless SDIO devices
>> +
>> +This node provides properties for controlling the Broadcom wireless
>> device. The
>> +node is expected to be specified as a child node to the MMC
>> controller that
>> +connects the device to the system.
>> +
>> +Required properties:
>> +
>> + - compatible : Should be "brcm,bcm43xx-fmac".
>> + - wlan-supply : phandle for fixed regulator used to control power for
>> +    the device/module.
> 
> The BCM43xx WLAN chips I used to work always have been controlled by a
> simple power enable GPIO of the chip itself. Has this changed in newer
> chips?
> 
> If you need to simply toggle a GPIO to control the power, you don't need
> to use the regulator API at all, controlling the GPIO directly.

Not sure I understand. Do you really mean 'chip' or 'wifi module' here.
The chip needs to be powered and for that it is hooked up to a
host/module provided GPIO (at least that is my understanding).

>> +
>> +Optional properties:
>> + - drive-strength : drive strength used for SDIO pins on device
>> (default = 6mA).
> 
> This should be a part of the MMC binding, I think. Probably also moved
> under MMC controller's node, since it's a board-specific property
> altering the parameters of the MMC controller, not the WLAN chip.

It is an electrical interfacing parameter between MMC controller and the
device. The specified drive-strength here is used to configure the PMU
on the chip so it is really related to the the chip.

>> + - interrupt-parent : the phandle for the interrupt controller to
>> which the
>> +    device interrupt (HOST_WAKE) is connected.
>> + - interrupts : interrupt specifier encoded according the interrupt
>> controller
>> +    specified by interrupt-parent property.
> 
> I would also add a clock here, since the BCM43xx chips usually need a
> 32k clock to operate (or at least the ones I used to work with did). It
> can be optional, as not all systems can control this clock.
> 
>> +
>> +Example:
>> +
>> +mmc3: mmc@01c20000 {
>> +    pinctrl-0 = <&mmc3_pins>;
>> +    pinctrl-1 = <&wifi_host_wake>;
> 
> WLAN_HOST_WAKE pin (aka the OOB interrupt) is specific to the WLAN chip,
> so this should be rather configured in a pinctrl state of the WLAN chip
> itself.

You mean that pinctrl-1 should move inside the "brcm,bcm43xx-fmac" node,
right?

>> +    vmmc-supply = <&mmc3_supply>;
>> +    bus-width = <4>;
>> +
>> +    bcm4335: bcm4335@0 {
> 
> nit: Why @0, if there is no reg property under this node?

I am not fluent with devicetree specifications (yet) nor know all the
conventions.

> Best regards,
> Tomasz

Thanks,
Arend

>> +        compatible = "brcm,bcm43xx-fmac";
>> +        wlan-supply = <&wlan-reg>;
>> +        drive-strength = <4>;
>> +        interrupt-parent = <&gpx2>;
>> +        interrupts = <5 IRQ_TYPE_LEVEL_HIGH>;
>> +        interrupt-names = "HOST_WAKE";
>> +    };
>> +};
>> +
>>

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