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GPIO context during "suspend" (deepsleep0)

Dav01
Expert 2300 points 


Hi,
I find this patch-description for the evm-module a bit confusing:
 • WLAN_EN moved from GPIO1_16 to GPIO3_16 as GPIO1_16 is losing context during suspend
   http://processors.wiki.ti.com/index.php/WL18xx_Adding_WoWLAN

In the AM335x datasheet, "8.1.11 Device Modules and Power Management Attributes List", 
Only GPIO_0 is part of the PD_PER power domain while using the deepsleep0 mode.

I would assume moving the wilink enable-pin from gpio1_* to gpio0_* ?
andby the way, when the wiki refers to "suspend", which sleep-mode is the text refering to!?


Related:
I assume pinmux/padconf can keep it's pu or pd regardless of gpio bank. So this will only fail to work if we would have external pull-up/down's that would need to be overridden or control via mosfet's (say for level translators).


  • 0 in reply to Biser Gatchev-XID
    Expert 2300 points

    Hi Biser,

    The question is more AM335x specific than WL1x as I'm seeing this as an "active high" pin for controlling an external IC's ENable pi or gate on a transistor during deepsleep0.

    The patch I'm refering to has only to do with an errata for the AM335x eval-board during suspend loosing it's context. 

    I think it would be great if we could see an answer here.

    best David

  • 0 in reply to Dav01
    Expert 1355 points

    Hi David,

      I too faced similar problem, i solved this problem by re-configuring GPIOs which are losing context 

    when system goes to deep sleep mode. 

      exporting the gpio and setting the direction in /sys/class/gpio/  folder  when system is coming out  from deep sleep mode

    Rajeev battu

  • 0 in reply to Rajeev
    Expert 2300 points

    Hi Rajeev,

    Thanks for reply. I wonder if someone can guide me to how you are "supposed" to do this under linux.

    Normally you have your pinmux config setup during early boot, but I assume there are places to put this so it can also survive a suspend (deepsleep0) to resume operation. 

    Any guidance much appreciated.

    /David

  • 0 in reply to Dav01
    Expert 1355 points

    Hi David,

      In TI kernel itself there is built in functionality by which one can set the pins to retain pins context  after Suspend/Resume. You can get it in arch/arm/mach-omap2/mux33xx.c 

    By using am335x_save_padconf() & am335x_restore_padconf(). 

    Rajeev

  • 0 in reply to Rajeev
    Expert 2300 points

    Hi,

    Checking in on this old thread. I've been looking around to find some wiki / documentation around this subject in the 3.12 Kernel.

    I can see another mechanis in the .dts (am43xx_pinmux) for the new AM43xx dev-kits where wake/sleep (DS0) pin-states are defined, while under AM335x I can't find where this is done.

    Any guidance would be much appreciated

    Thanks David