BCM2048 bluetooth connected over OMAP serial

BCM2048 bluetooth connected over OMAP serial

[Pavel Machek]

Hi!

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 = <3>;
                  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?

Best regards,
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

BCM2048 bluetooth connected over OMAP serial

[Arnd Bergmann]

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.

	Arnd

BCM2048 bluetooth connected over OMAP serial

[Rob Herring]

On Wed, Dec 10, 2014 at 10:43 AM, Pavel Machek <pavel@ucw.cz> wrote:
> Hi!
>
> 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 = <3>;
>                   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?

Isn't the normal way for BT to work is the uart is exposed to
userspace and the BT stack is all in userspace? This is how other
Broadcom BT/WiFi combo parts work.

Rob

BCM2048 bluetooth connected over OMAP serial

[Marcel Holtmann]

Hi Rob,

>> 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 = <3>;
>>                  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?
> 
> Isn't the normal way for BT to work is the uart is exposed to
> userspace and the BT stack is all in userspace? This is how other
> Broadcom BT/WiFi combo parts work.

not on Linux actually. The Bluetooth core layer (including the HCI transport) are all in kernel space.

However UART based Bluetooth chips are exposed as TTY and then the N_HCI line discipline is used to attach it to the kernel Bluetooth subsystem.

Regards

Marcel

BCM2048 bluetooth connected over OMAP serial

[Mark Rutland]

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.

Mark.

BCM2048 bluetooth connected over OMAP serial

[Pavel Machek]

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.

Actually, the chip also has PCM, analog audio, and "pc compatible?"
connections, plus some connection to WIFI. So we may need more
phandles there....

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

BCM2048 bluetooth connected over OMAP serial

[sre@debian.org]

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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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 at debian.org <sre@kernel.org> 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
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

BR,

marek

-- 
as simple and primitive as possible
-------------------------------------------------
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Freelance Developer

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