[Letux-kernel] gta04a5 + bluetooth + letux 4.19.0.3 = mysterious things ahead

Andreas Kemnade andreas at kemnade.info
Tue Nov 6 07:36:34 CET 2018


Hi,

On Mon, 5 Nov 2018 11:59:04 +0100
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> > Am 05.11.2018 um 07:38 schrieb Andreas Kemnade <andreas at kemnade.info>:
> > 
> > Hi,
> > 
> > On Sun, 4 Nov 2018 19:40:48 +0100
> > "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> >   
> >>> Am 04.11.2018 um 15:18 schrieb Andreas Kemnade <andreas at kemnade.info>:
> >>> 
> >>> Hi,
> >>> 
> >>> I am wondering about bluetooth behavior on a5:
> >>> 
> >>> - Suspend current decrease by 6mA (I have seen 12mA suspend without
> >>> modem): my doing the following steps
> >>>  1. booting without bluetoothd, module autoloading, no uart idling
> >>>  2. hciconfig hci0 up (it is still down)
> >>>  3. rmmod hci_uart
> >>>  4. suspend
> >>> 
> >>> To clarify 6mA lower than without modules.
> >>>   
> > I am wondering what happens here. This sequence changes something.
> > But what?
> > -External pin state
> > - CTS/RTS / PCM pins?  
> 
> probably yes. AFAIR pins are input by default and pinmux is only set
> up if driver is loaded.
> 
Well, the driver (omap-uart) is statically compiled in, so it is already
loaded. Pinmux is set by uboot and then maybe overwritten later.
Maybe the gta04a3/4 settings set by uboot are causing strange
things. CTS/RTS pinmux is not set in kernel but in uboot.

> > -Internal state of the module (but it should be..off anyways)
> > -Internal state of the soc
> > -energy harvesting functionality of the bt/wifi combo module ;-)  
> 
> Yes, that is it. If you find the right sequence you can get to
> negative suspend current :)
> 
Yes, the sequence is critical. It makes even a difference if you
have serial autosuspend enabled. modprobe/rmmod hci_uart with too less
modules loaded seems not to influence suspend current.
It influences idle current if uarts are not auto-suspended.
Unfortunately I have not found the right sequence yet to have
that negative suspend current ;-)

Regards,
Andreas
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