linux-kernel - [BISECTED] Allwinner A33 tablet does not fully power off

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Message-ID: <9f8a0fc3-1d9a-b271-3c26-4f7373b8a3e9@gmail.com>
Date:   Sat, 29 Oct 2022 18:23:43 +0300
From:   Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:     wens@...e.org, samuel@...lland.org
Cc:     mripard@...nel.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Merlijn Wajer <merlijn@...zup.org>
Subject: [BISECTED] Allwinner A33 tablet does not fully power off

Hi,

After commit 843107498f91e57d1d4b22cd8787112726fdaeb4 (bus: sunxi-rsb: 
Implement suspend/resume/shutdown callbacks) Q8 A33 tablet I have here 
cannot be powered-on after power-off, it needs press-and-hold of the 
power button for 10 seconds (I guess some HW assisted power down 
happens) before it can be powered-on again.

The following patch makes it behave correctly:

diff --git a/drivers/bus/sunxi-rsb.c b/drivers/bus/sunxi-rsb.c
index 60b082fe2ed0..30016d62044c 100644
--- a/drivers/bus/sunxi-rsb.c
+++ b/drivers/bus/sunxi-rsb.c
@@ -818,10 +818,7 @@ static int sunxi_rsb_remove(struct platform_device 
*pdev)

  static void sunxi_rsb_shutdown(struct platform_device *pdev)
  {
-       struct sunxi_rsb *rsb = platform_get_drvdata(pdev);
-
         pm_runtime_disable(&pdev->dev);
-       sunxi_rsb_hw_exit(rsb);
  }

  static const struct dev_pm_ops sunxi_rsb_dev_pm_ops = {

I guess the issue comes from the fact that by the time 'power off' 
command to the power management IC has to be send, the bus it lives on 
is already down, so the device is left in semi-powered down state. Ofc 
this is a wild guess, however, preventing the bus being turned off on 
shutdown fixes the issue.

Please LMK if the above is the correct approach so I will send a proper 
patch or something else shall be fixed.

Ivo