Re: [PATCH] twl4030 reboot workaround

[Mike Turquette <mturquette@ti.com>]

Mikko Rapeli wrote:
> From: Mikko Rapeli <ext-mikko.rapeli@nokia.com>
> 
> Original patch: http://marc.info/?l=linux-omap&m=126522625032441&w=2

I forgot about this one...

> "Removes TWL4030 sleep script prior to rebooting, only on OMAP3. This is
> necessary since DPLL3 reset causes SYS_OFFMODE pin to go low, resulting
> in the sleep script being executed on TWL4030. This usually results in
> VDD1 & VDD2 voltage collapse while ROM code is executing, followed by an
> MPU Watch Dog reset or worse, an irrecoverable hang."
> 
> Original patch resulted in a crash due to sleeping i2c calls late in the
> reboot sequence. Here's how to trigger the crash:
> 
> 	# cat /dev/urandom > /foo &
> 	sync();
>         reboot(LINUX_REBOOT_CMD_RESTART2);
> 
> Kernel trace from 2.6.32:
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = c0004000
> [00000000] *pgd=00000000
> Internal error: Oops: 805 [#2] PREEMPT
> ...
> [<c00b3210>] (exit_mmap+0x1d4/0x1f8) from [<c006069c>] (mmput+0x34/0x110)
> [<c006069c>] (mmput+0x34/0x110) from [<c0064a90>] (exit_mm+0x140/0x180)
> [<c0064a90>] (exit_mm+0x140/0x180) from [<c00668ec>] (do_exit+0x5d8/0x6ac)
> [<c00668ec>] (do_exit+0x5d8/0x6ac) from [<c0035858>] (die+0x2d4/0x2e0)
> [<c0035858>] (die+0x2d4/0x2e0) from [<c0035904>] (baddataabort+0x0/0x50)
> [<c0035904>] (baddataabort+0x0/0x50) from [<c0274ff4>] (i2c_transfer+0xec/0x104)
> [<c0274ff4>] (i2c_transfer+0xec/0x104) from [<00000001>] (0x1)
> 
> Fix is to move reboot preparations into a reboot notifier.
> 
> Signed-off-by: Mikko Rapeli <ext-mikko.rapeli@nokia.com>
> ---
>  drivers/mfd/twl4030-power.c |   29 +++++++++++++++++++++++++++++
>  1 files changed, 29 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/mfd/twl4030-power.c b/drivers/mfd/twl4030-power.c
> index 7efa878..5d46768 100644
> --- a/drivers/mfd/twl4030-power.c
> +++ b/drivers/mfd/twl4030-power.c
> @@ -28,6 +28,7 @@
>  #include <linux/pm.h>
>  #include <linux/i2c/twl.h>
>  #include <linux/platform_device.h>
> +#include <linux/reboot.h>
>  
>  #include <asm/mach-types.h>
>  
> @@ -127,6 +128,29 @@ static u8 res_config_addrs[] = {
>  	[RES_Main_Ref]	= 0x94,
>  };
>  
> +/*
> + * PRCM on OMAP3 will drive SYS_OFFMODE low during DPLL3 warm reset.
> + * This causes Gaia sleep script to execute, usually killing VDD1 and
> + * VDD2 while code is running.  WA is to disable the sleep script
> + * before warm reset.
> + */
> +static int twl4030_prepare_for_reboot(struct notifier_block *this,
> +		unsigned long cmd, void *p)
> +{
> +	int err;
> +	err = twl4030_remove_script(TWL4030_SLEEP_SCRIPT);
> +	if (err)
> +		pr_err("TWL4030: error trying to disable sleep script!\n");
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block twl4030_reboot_notifier = {
> +		.notifier_call = twl4030_prepare_for_reboot,
> +		.next = NULL,
> +		.priority = 0
> +};
> +
>  static int __init twl4030_write_script_byte(u8 address, u8 byte)
>  {
>  	int err;
> @@ -549,6 +573,11 @@ void __init twl4030_power_init(struct twl4030_power_data *twl4030_scripts)
>  	err = twl_i2c_write_u8(TWL4030_MODULE_PM_MASTER, 0, R_PROTECT_KEY);
>  	if (err)
>  		pr_err("TWL4030 Unable to relock registers\n");
> +
> +	err = register_reboot_notifier(&twl4030_reboot_notifier);

This method is much better than the method I proposed before.  Taking 
into account the comments from others, ACK.

Mike

> +	if (err)
> +		pr_err("TWL4030 Failed to register reboot notifier\n");
> +
>  	return;
>  
>  unlock: