Re: BCM2048 bluetooth connected over OMAP serial

[Belisko Marek]

Neil Brown send series which implement what was suggested in previous posts:
https://lkml.org/lkml/2014/12/11/454

On Wed, Dec 10, 2014 at 11:50 PM, sre@xxxxxxxxxx <sre@xxxxxxxxxx> wrote:
> Hi,
>
> On Wed, Dec 10, 2014 at 09:56:22PM +0100, Pavel Machek wrote:
>> On Wed 2014-12-10 18:42:03, Mark Rutland wrote:
>> > On Wed, Dec 10, 2014 at 05:02:42PM +0000, Arnd Bergmann wrote:
>> > > On Wednesday 10 December 2014 17:43:33 Pavel Machek wrote:
>> > > >
>> > > > So, there's bluetooth chip that's connected to the SoC by UART and some
>> > > > GPIOs. What would be right representation in the device tree?
>> > > > Something like this?
>> > > >
>> > > >         bluetooth {
>> > > >                   compatible = "broadcom,bcm2048";
>> > > >                   uart = <&uart2>;
>> > > >                   reset-gpios = <&gpio3 27 GPIO_ACTIVE_HIGH>; /* want 91 */
>> > > >                   host-wakeup-gpios = <&gpio4 5 GPIO_ACTIVE_HIGH>; /* want 101 */
>> > > >                   bluetooth-wakeup-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>; /* want 37 */
>> > > >                   chip-type = >;
>> > > >                   bt-sysclk = <2>;
>> > > >                   reset-gpio-shared = <0>;
>> > > >         };
>> > > >
>> > > > Is there some way to prevent OMAP tty driver from binding to the
>> > > > device and exporting the device to userspace?
>> > >
>> > > I think from the driver perspective, you want this to be a tty line
>> > > discipline rather than a driver that attaches to the physical
>> > > uart.
>> > >
>> > > For the DT representation, I fear we haven't got a precedent. A uart
>> > > phandle sounds reasonable, but there might be other ways to do it
>> > > and we should consider if there are better alternatives. It could
>> > > possibly be a child node of the uart, but that would require other
>> > > infrastructure in the kernel because we don't currently create
>> > > devices for those.
>> >
>> > I think the child node is the way to go; that would match what we do for
>> > I2C and SPI. We might need new infrastructure, but I don't think we
>> > should treat this differently simlpy because we don't have that yet.
>>
>> Well, uart in this case looks more like a GPIO than an I2C (no
>> addressing, just few wires). And we do phandle for GPIOs.
>
> Right and the devices use I2C for full communication and GPIOs as
> helpers. I guess UART counts as full communication and not as helper.
>
> phandle vs child node is not a matter of adressing and btw where is
> the difference between "5th gpio on 1st gpio controller" and "5th
> address on 1st i2c controller"?
>
>> Actually, the chip also has PCM, analog audio, and "pc compatible?"
>> connections, plus some connection to WIFI. So we may need more
>> phandles there....
>
> This is much harder to solve. I think we don't have a DT binding for
> a device, which uses two communication interfaces as the bcm2048
> (uart & i2c). OTOH we may just add a slave device for the fm-radio
> part like this:
>
> uart {
>     bcm2048 {
>         stuff;
>     };
> };
>
> i2c {
>     bcm2048-radio {
>         master = <&bcm2048>;
>     };
> };
>
> -- Sebastian
>
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>

BR,

marek

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