[Buildroot] [PATCH v2] raspberrypi3: fix serial console (load pi3-miniuart-bt overlay)

[Peter Seiderer]

Hello Martin,

On Mon, 9 May 2016 14:19:48 +0100, Martin Bark <martin at barkynet.com> wrote:

> Peter,
> 
> On 3 May 2016 at 20:02, Peter Seiderer <ps.report at gmx.net> wrote:
> > Hello Martin,
> >
> > On Tue, 3 May 2016 11:23:50 +0100, Martin Bark <martin at barkynet.com> wrote:
> >
> >> All,
> >>
> >> On 3 May 2016 at 07:18, Peter Korsgaard <peter at korsgaard.com> wrote:
> >> >>>>>> "Oscar" == Oscar Gomez Fuente <oscargomezf at gmail.com> writes:
> >> >
> >> >  > Hi Peter Seiderer,
> >> >  > What's the difference between enabling pi3-miniuart-bt instead of
> >> >  > pi3-disable-bt?
> >> >
> >> >  > With pi3-disable-bt enables it works fine the serial console on (14 [TxD] &
> >> >  > 15 [RxD] pins).
> >> >
> >> > From the names I would guess it is the difference between completely
> >> > disabling access to the bluetooth module and providing access to it
> >> > though the secondary (mini) uart.
> >> >
> >> > The miniuart has some limitations, but I guess basic bluetooth stuff
> >> > should work with it.
> >>
> >> I've got a bit lost in the rpi3 serial console issues but as i
> >> understand the current situation all you need to do is set
> >> enable_uart=1 in config.txt.  See
> >> https://github.com/raspberrypi/firmware/issues/553#issuecomment-199486644.
> >> I've not tested this.
> >>
> >> I think you also need to change cmdline.txt to use console=serial0 as
> >> the pi3-miniuart-bt will replace it with the correct serial device
> >> (ttyAMA0 or ttyS0) depending if it's enabled or not.  See the comments
> >> in https://github.com/raspberrypi/linux/blob/rpi-4.1.y/arch/arm/boot/dts/overlays/pi3-miniuart-bt-overlay.dts.
> >>
> >
> > This works too, not sure whats the better solution, explicit via device tree overlay
> > or some firmware magic....
> >
> > - pi3-miniuart-bt 'dmesg | grep tty':
> > [    0.000000] Kernel command line: 8250.nr_uarts=1 dma.dmachans=0x7f35 bcm2708_fb.fbwidth=1920 bcm2708_fb.fbheight=1200 bcm2709.boardrev=0xa02082 bcm2709.serial=0xa60340 smsc95xx.macaddr=B8:27:EB:A6:03:40 bcm2708_fb.fbswap=1 bcm2709.uart_clock=48000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000  root=/dev/mmcblk0p2 rootwait console=tty1 console=ttyAMA0,115200
> > [    0.001320] console [tty1] enabled
> > [    0.318181] 3f215040.uart: ttyS0 at MMIO 0x3f215040 (irq = 59, base_baud = 50000000) is a 16550
> > [    2.008162] 3f201000.uart: ttyAMA0 at MMIO 0x3f201000 (irq = 87, base_baud = 0) is a PL011 rev2
> > [    3.296233] console [ttyAMA0] enabled
> >
> > - enable-uart=1, serial0 dmesg | grep tty':
> > [    0.000000] Kernel command line: 8250.nr_uarts=1 dma.dmachans=0x7f35 bcm2708_fb.fbwidth=1920 bcm2708_fb.fbheight=1200 bcm2709.boardrev=0xa02082 bcm2709.serial=0xa60340 smsc95xx.macaddr=B8:27:EB:A6:03:40 bcm2708_fb.fbswap=1 bcm2709.uart_clock=48000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000  root=/dev/mmcblk0p2 rootwait console=tty1 console=ttyS0,115200
> > [    0.001318] console [tty1] enabled
> > [    0.318270] console [ttyS0] disabled
> > [    0.318389] 3f215040.uart: ttyS0 at MMIO 0x3f215040 (irq = 59, base_baud = 31250000) is a 16550
> > [    1.042714] console [ttyS0] enabled
> > [    3.020277] 3f201000.uart: ttyAMA0 at MMIO 0x3f201000 (irq = 87, base_baud = 0) is a PL011 rev2
> >
> 
> I wonder if the solution is to just document the situation in
> board/raspberrypi/readme.txt.  The documentation could just detail the
> available choices for Bluetooth and serial console on the rpi3 and how
> to configure each manually.  A summary of the available choices is:
> 
> 1) Default setup - Serial console does not work, Bluetooth works
> 2) Add enable-uart=1 - Serial console works but the core frequency is
> fixed.  Serial console max baud rate is less than the rpi2. Bluetooth
> works.
> 3) Use pi3-miniuart-bt - Serial console works the same as the rpi2 but
> Bluetooth runs slow.
> 4) Use pi3-disable-bt - Serial console works the same as the rpi2 but
> Bluetooth is disabled.
> 
> What do you think?

Agreed, with bias to 3) as the default (or one of the other solutions with
serial console enabled)...

Regards,
Peter

> 
> Thanks
> 
> Martin
> 
> > Regards,
> > Peter
> >
> >
> >> Thanks
> >>
> >> Martin
> >>
> >> >
> >> > --
> >> > Venlig hilsen,
> >> > Peter Korsgaard
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> >