[U-Boot] FW: Don't get any interrupts once I boot into Linux

[Greg Topmiller]

Thanks Benoit,

I also tried changing the uboot V2012.07, file arm/cpu/armv7/timer.c  to use  the IPG clock rather than the 32Khz but no difference.

It looks like the FSL interrupt initialization is in arch/arm/plat-mxc/tzic.c file.  I don't see anything obvious.  It's not real big.  I have a Lauterbach debugger that I have been using to step thru the Linux code.  The mxc_timer_interrupt never occurs.


Best Regards,
Greg

-----Original Message-----
From: Benoît Thébaudeau [mailto:benoit.thebaudeau at advansee.com]
Sent: Friday, September 14, 2012 12:06 PM
To: Fabio Estevam
Cc: u-boot at lists.denx.de; Greg Topmiller; gildas allain
Subject: Re: [U-Boot] Don't get any interrupts once I boot into Linux

Hi Fabio, Greg,

On Friday, September 14, 2012 5:15:17 PM, Fabio Estevam wrote:
> On Fri, Sep 14, 2012 at 12:04 PM, Greg Topmiller 
> <Greg.Topmiller at jdsu.com> wrote:
> > I downloaded the V2012.07 version of u-boot from the git.denx.de 
> > repository and built it for our target.  U-boot boots up properly 
> > and I can use the commands but now when I boot into Linux I don't 
> > seem to be getting interrupts.  The Linux kernel hangs in the 
> > calculate_delay function waiting for ticks != jiffies.  I do not get 
> > the interrupt for the timer.  I have verified that our previous 
> > u-boot that is based on the 2009.12 version with Freescale patches 
> > does work.  The timer interrupt occurs and jiffies is incremented 
> > allowing the loop to exit.  Any help would be appreciated.
> >
> 
> Which board are you using?

Same here with a custom i.MX51-based board and a FSL-based Linux. It works fine with the FSL-based U-Boot (2009.12).

Some debugging has shown that:
 - The Linux timer is based on GPT.
 - The GPT counter runs fine at 8 Mincrements/s as expected.
 - The interrupt handler is never called.
 - The interrupt is based on output compare, but forcing the OC value a little
   bit after the counter value does not trigger the interrupt handler.
 - Resetting the GPT and clearing its registers prior to Linux timer init does
   not help.
 - There does not seem to be any wait or sleep modes involved.
 - In this loop, CPSR shows supervisor mode with FIQ disabled and IRQ enabled
   (same for both U-Boot versions).
 - This version of Linux does not set VBAR. Neither does the older U-Boot
   contrary to the latest, but setting VBAR to 0 like with the older U-Boot does
   not help.

The differences in system registers between these U-Boots are really small and seem insignificant. The GPT clock source used by these versions is different, but that should not be an issue with proper reinitialization in Linux.

The i.MX51 errata don't mention any issue like that, at least for GPT.
ENGcm09114 is similar, but in a very different context.

The next step is to dig into the interrupt controller settings and vectors to check that Linux sets up everything properly. This issue is very likely caused by this FSL Linux that unduly relies on the bootloader to initialize something.

Best regards,
Benoît