[PATCH 3/4] ARM: dts: bcm2835-rpi-zero-w: Add bcm43438 serial slave

[Marcel Holtmann]

Hi Stefan,

>>>>> Add BCM43438 (bluetooth) as a serdev slave device of uart0 (pl011/ttyAMA0).
>>>>> This allows to automatically insert the bcm43438 to the bluetooth
>>>>> subsystem instead of relying on patched userspace helpers (hciattach).
>>>>> 
>>>>> In order to keep a debug UART we need to switch to uart1.
>>>>> 
>>>>> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
>>>>> ---
>>>>> arch/arm/boot/dts/bcm2835-rpi-zero-w.dts | 14 +++++++++++++-
>>>>> 1 file changed, 13 insertions(+), 1 deletion(-)
>>>>> 
>>>>> diff --git a/arch/arm/boot/dts/bcm2835-rpi-zero-w.dts b/arch/arm/boot/dts/bcm2835-rpi-zero-w.dts
>>>>> index cf53436..b7f79f1 100644
>>>>> --- a/arch/arm/boot/dts/bcm2835-rpi-zero-w.dts
>>>>> +++ b/arch/arm/boot/dts/bcm2835-rpi-zero-w.dts
>>>>> @@ -131,6 +131,18 @@
>>>>> 
>>>>> &uart0 {
>>>>> 	pinctrl-names = "default";
>>>>> -	pinctrl-0 = <&uart0_gpio14>;
>>>>> +	pinctrl-0 = <&uart0_gpio32 &uart0_ctsrts_gpio30>;
>>>>> +	status = "okay";
>>>>> +
>>>>> +	bluetooth {
>>>>> +		compatible = "brcm,bcm43438-bt";
>>>>> +		max-speed = <2000000>;
>>>>> +		shutdown-gpios = <&gpio 45 GPIO_ACTIVE_HIGH>;
>>>>> +	};
>>>>> +};
>>>> 
>>>> is the shutdown GPIO working as expected with this hardware. So even module unload and reload works fine?
>>> 
>>> Yes, unload and reload works fine. 
>>> 
>>>> Meaning we are getting back to the 115200 default baud rate on the UART?
>>> 
>>> I assume that, because reload works as expected. 
>> 
>> awesome. That is good news.
>> 
>> Since you said that the GPIO expander driver for the RPi 3 has been accepted, did you test it there as well? If so, then it would be good to get a patch that also provides shutdown-gpios for RPi 3.
> 
> so here comes the bad news. hci_bcm uses gpiod_set_value() which is for interrupt context, but the gpio expander can sleep. So we will get this warning:
> 
> [    4.802447] ------------[ cut here ]------------
> [    4.802485] WARNING: CPU: 3 PID: 91 at drivers/gpio/gpiolib.c:2986 gpiod_set_value+0x50/0x58
> [    4.802489] Modules linked in: hci_uart ac97_bus btbcm snd_pcm_dmaengine bluetooth snd_pcm snd_timer ecdh_generic snd soundcore bcm2835_thermal crc32_arm_ce
> [    4.802543] CPU: 3 PID: 91 Comm: kworker/u8:2 Not tainted 4.16.0-rc3-next-20180302-dirty #4
> [    4.802547] Hardware name: BCM2835
> [    4.802562] Workqueue: events_unbound async_run_entry_fn
> [    4.802593] [<c03119a4>] (unwind_backtrace) from [<c030cc24>] (show_stack+0x10/0x14)
> [    4.802612] [<c030cc24>] (show_stack) from [<c0d8e9dc>] (dump_stack+0x8c/0xa0)
> [    4.802628] [<c0d8e9dc>] (dump_stack) from [<c0343a2c>] (__warn+0xe0/0xf8)
> [    4.802640] [<c0343a2c>] (__warn) from [<c0343b5c>] (warn_slowpath_null+0x40/0x48)
> [    4.802652] [<c0343b5c>] (warn_slowpath_null) from [<c06d0de0>] (gpiod_set_value+0x50/0x58)
> [    4.802693] [<c06d0de0>] (gpiod_set_value) from [<bf0e2e90>] (bcm_gpio_set_shutdown+0xc/0x14 [hci_uart])
> [    4.802757] [<bf0e2e90>] (bcm_gpio_set_shutdown [hci_uart]) from [<bf0e2a64>] (bcm_gpio_set_power+0x18/0x140 [hci_uart])
> [    4.802806] [<bf0e2a64>] (bcm_gpio_set_power [hci_uart]) from [<bf0e2e4c>] (bcm_serdev_probe+0x64/0x9c [hci_uart])
> [    4.802848] [<bf0e2e4c>] (bcm_serdev_probe [hci_uart]) from [<c08f2528>] (driver_probe_device+0x254/0x32c)
> [    4.802863] [<c08f2528>] (driver_probe_device) from [<c08f26a4>] (__driver_attach+0xa4/0xa8)
> [    4.802878] [<c08f26a4>] (__driver_attach) from [<c08f08b8>] (bus_for_each_dev+0x74/0xb4)
> [    4.802895] [<c08f08b8>] (bus_for_each_dev) from [<c0366498>] (async_run_entry_fn+0x44/0x108)
> [    4.802910] [<c0366498>] (async_run_entry_fn) from [<c035d594>] (process_one_work+0x200/0x4f8)
> [    4.802923] [<c035d594>] (process_one_work) from [<c035e4a8>] (worker_thread+0x4c/0x5d4)
> [    4.802938] [<c035e4a8>] (worker_thread) from [<c0363300>] (kthread+0x150/0x158)
> [    4.802952] [<c0363300>] (kthread) from [<c03010e8>] (ret_from_fork+0x14/0x2c)
> [    4.802957] Exception stack(0xed959fb0 to 0xed959ff8)
> [    4.802966] 9fa0:                                     00000000 00000000 00000000 00000000
> [    4.802977] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [    4.802986] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [    4.802993] ---[ end trace b947f9d4c40fa261 ]—

that is weird since we should be either in a probe context or in hdev->open context and both can sleep as far as I know.

Regards

Marcel