Subject: Boot hang regression 3.10.0-rc4 -> 3.10.0

From: [email-masked] (Rajendra Nayak)
Date: Thu, 11 Jul 2013 11:48:39 +0530

On Wednesday 10 July 2013 07:56 PM, Tony Lindgren wrote:
> * Kevin Hilman <[email-masked]> [130710 01:29]:
>> Felipe Balbi <[email-masked]> writes:
>>>>
>>>> Right, but calling serial_omap_restore_context() even when the context
>>>> is not lost, should not ideally cause an issue.
>>>
>>> it does in one condition. If context hasn't been saved before. And that
>>> can happen in the case of wrong pm runtime status for that device.
>>>
>>> Imagine the device is marked as suspended even though it's fully enabled
>>> (it hasn't been suspended by hwmod due to NO_IDLE flag). In that case
>>> your context structure is all zeroes (context has never been saved
>>> before) then when you call pm_runtime_get_sync() on probe() your
>>> ->runtime_resume() will get called, which will restore context,
>>> essentially undoing anything which was configured by u-boot.
>>>
>>> Am I missing something ?
>>
>> You're right, the _set_active() is crucial in the case when we prevent
>> the console UART from idling during boot (though that shouldn't be
>> happening in mainline unless the fix for "Issue 1" is done.)
> 
> Felipe is right, looks like all we need is to check if context is
> initialized or not. So no need for mach-omap2/serial.c or hwmod tinkering.
> 
> After that having DEBUG_LL and cmdline with earlyprintk console=ttyO..
> works for me.

On what platform? Like I said there are flags set statically in hmwod
data for OMAP4 and OMAP5, which make it work without any hwmod tinkering
in mach-omap2/serial.c. But it won't work for am33xx.

 We could also check for some combination of the context
> save registers being NULL if somebody has a good idea which ones
> should never be 0.
> 
> Regards,
> 
> Tony
> 
> 
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -161,6 +161,7 @@ struct uart_omap_port {
>  	u32			calc_latency;
>  	struct work_struct	qos_work;
>  	struct pinctrl		*pins;
> +	bool			initialized;
>  	bool			is_suspending;
>  };
>  
> @@ -1523,6 +1524,8 @@ static int serial_omap_probe(struct platform_device *pdev)
>  
>  	pm_runtime_mark_last_busy(up->dev);
>  	pm_runtime_put_autosuspend(up->dev);
> +	up->initialized = true;

This won't help as the context save for serial happens as part of set_termios() and not
when the device is probed.

> +
>  	return 0;
>  
>  err_add_port:
> @@ -1584,6 +1587,9 @@ static void serial_omap_mdr1_errataset(struct uart_omap_port *up, u8 mdr1)
>  #ifdef CONFIG_PM_RUNTIME
>  static void serial_omap_restore_context(struct uart_omap_port *up)
>  {
> +	if (!up->initialized)
> +		return;
> +
>  	if (up->errata & UART_ERRATA_i202_MDR1_ACCESS)
>  		serial_omap_mdr1_errataset(up, UART_OMAP_MDR1_DISABLE);
>  	else
>