[Letux-kernel] Turning off 3g in uboot

[H. Nikolaus Schaller]

> Am 01.02.2017 um 17:26 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> Hi,
> 
> I remember a paragraph in the gta04 user guide:
> 
> Note: if the CPU is powered down through the emergency function (Power
> button pressed for >8 seconds) the module may remain powered on,
> although everything else is off. Although it typically draws only 3-10
> mA it may try to re-register to the network and in certain conditions
> (signal received from the base station is better than the own
> transmitted signal) it may draw up to 100 mA and send GSM bursts while
> unsuccessfully trying to re- register to base stations. It should be
> possible to handle that by some U-Boot hack (U-Boot starts but shuts
> down after release of the Power button).

Yes, this still seems to be the case according to the console log, although
I don't know how U-Boot recognises to shut down immediately in this situation.

Here is what I see right after 8 seconds elapsed after pressing the button.
The auto-reboot repeats until I release the power-button:

U-Boot SPL 2016.11-00211-g7620f06 (Jan 30 2017 - 18:09:58)
Trying to boot from OneNAND
spl: onenand
spl: payload image: *s load addr: 0x4 size: -2146435040
Jumping to U-Boot
loaded - jumping to U-Boot...

U-Boot 2016.11-00211-g7620f06 (Jan 30 2017 - 18:09:58 +0100)

OMAP36XX/37XX-GP ES1.2, CPU-OPP2, L3-200MHz, Max CPU Clock 1 Ghz
GTA04 + LPDDR/OneNAND
I2C:   ready
DRAM:  512 MiB
NAND:  Muxed OneNAND 512MB 1.8V 16-bit (0x50)
OneNAND version = 0x0232
Chip support all block unlock
Chip has 4KiB pagesize
Scanning device for bad blocks
onenand_bbt_wait: controller error = 0x0400
Bad eraseblock 843 at 0x0d2c0000
OneNAND: 512 MiB
MMC:   OMAP SD/MMC: 0

U-Boot SPL 2016.11-00211-g7620f06 (Jan 30 2017 - 18:09:58)
Trying to boot from OneNAND
spl: onenand
spl: payload image: *s load addr: 0x4 size: -2146435040
Jumping to U-Boot
loaded - jumping to U-Boot...

U-Boot 2016.11-00211-g7620f06 (Jan 30 2017 - 18:09:58 +0100)

OMAP36XX/37XX-GP ES1.2, CPU-OPP2, L3-200MHz, Max CPU Clock 1 Ghz
GTA04 + LPDDR/OneNAND
I2C:   ready
DRAM:  512 MiB
NAND:  Muxed OneNAND 512MB 1.8V 16-bit (0x50)
OneNAND version = 0x0232
Chip support all block unlock
Chip has 4KiB pagesize
Scanning device for bad blocks
onenand_bbt_wait: controller error = 0x0400
Bad eraseblock 843 at 0x0d2c0000
OneNAND: 512 MiB
MMC:   OMAP SD/MMC: 0

### here happens the power-button detection ###

We might find it in the initialization function table of u-boot
(there is an array of function pointers doing i2c, dram, nand,
mmc, ... in this sequence).

> 
> 
> What are the opinions about that now? If I understand correctly that
> should be doable more easily on GTA04A5.

Yes.

There are two gpios to handle this. We can try to read the "modem is
active gpio" (twl_gpio 6) and try to make a 200ms impulse on the on-key gpio
(&gpio6 26 = GPIO_186).

We do not have to restrict this to the emergency-power-off situation
but can do it for every u-boot startup. If the modem happens to be
already on, we can try to power it off (and use board-detection to
restrict this to GTA04A5).

BR,
Nikolaus

PS: I hope that we can easily read the twl gpios in U-Boot...
i2c seems to be available at the critical point.
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