[PATCH v3 2/3] ARM: dts: bcm2837-rpi-3-b: Add bcm43438 as serial slave

[Rob Herring]

On Tue, Aug 15, 2017 at 8:06 AM, Marcel Holtmann <marcel at holtmann.org> wrote:
> Hi Rob,
>
>> Add BCM43438 as a slave device of uart0 (pl011/ttyAMA0).
>> This allows to automatically insert the bcm43438 to the bluetooth
>> subsystem instead of relying on userspace helpers (hciattach).
>>
>> Overwrite bootargs to use 8250 aux uart (ttyS0) as console instead
>> of pl011/ttyAMA0.
>>
>> Signed-off-by: Loic Poulain <loic.poulain at gmail.com>
>> ---
>> v2: dt-bindings as separate patch
>>     rebase on upcoming pi3 dts changes
>> v3: changes in bcm serdev drivers:
>>     name refactoring and additional comments
>>     Add generic host_set_baudrate method
>>     Use agnostic device_property_read
>>
>> arch/arm/boot/dts/bcm2837-rpi-3-b.dts | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/arch/arm/boot/dts/bcm2837-rpi-3-b.dts b/arch/arm/boot/dts/bcm2837-rpi-3-b.dts
>> index 20725ca..5abc1df 100644
>> --- a/arch/arm/boot/dts/bcm2837-rpi-3-b.dts
>> +++ b/arch/arm/boot/dts/bcm2837-rpi-3-b.dts
>> @@ -8,6 +8,11 @@
>>       compatible = "raspberrypi,3-model-b", "brcm,bcm2837";
>>       model = "Raspberry Pi 3 Model B";
>>
>> +     chosen {
>> +             /* 8250 auxiliar UART instead of pl011 */
>> +             bootargs = "earlyprintk console=ttyS0,115200";
>> +     };
>> +
>>       memory {
>>               reg = <0 0x40000000>;
>>       };
>> @@ -24,6 +29,11 @@
>>       pinctrl-names = "default";
>>       pinctrl-0 = <&uart0_gpio32 &gpclk2_gpio43>;
>>       status = "okay";
>> +
>> +     bluetooth {
>> +             compatible = "brcm,bcm43438-bt";
>> +             max-speed = <921600>;
>> +     };
>> };
>
> I know that hci_ll.c DT entry also uses max-speed for the naming. Is this something common we should be doing? Essentially it is not really max-speed. It is the operational speed that we are configuring. There is no down negotiation ongoing. Does it make sense to use oper-speed instead?

max-speed is correct to use. By default, a driver should know the max
speed of a device (implied by the compatible). The DT property is only
for when there is some host or board limitation as this case seems to
be.

> Are we otherwise fine with compatible string naming?

Yes.

Rob

>
> Loic, the hciattach examples list 3000000 as operational speed. Any reason why we should limit it?
>
> Regards
>
> Marcel
>