Problem with Busybox shell

Problem with Busybox shell

[MohanReddy koppula]

Hi All,

I am working on an MPC885 based custom board. I am able to boot up the
linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
is not accepting any inputs, I am not able to enter any command, it
just hangs there. I am using ttyCPM0 terminal.

I suspected if there was any problem in CPM driver interrupts
generation and put some printk's in the interrupt handler and could
see interrupts are raised and data is read, but shell is not taking
the input.

I wrote an init.c and opened the ttyCPM0 and tried to read from it,
but couldn't. I am able to write to ttyCPM0 and see it on the host
minicom.

Please some one help me.

thanks in advance for your help.

-Mohan

Re: Problem with Busybox shell

[Scott Wood]

On Tue, 18 Jan 2011 07:54:42 -0500
MohanReddy koppula <mohanreddykv@gmail.com> wrote:

> Hi All,
> 
> I am working on an MPC885 based custom board. I am able to boot up the
> linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
> is not accepting any inputs, I am not able to enter any command, it
> just hangs there. I am using ttyCPM0 terminal.
> 
> I suspected if there was any problem in CPM driver interrupts
> generation and put some printk's in the interrupt handler and could
> see interrupts are raised and data is read, but shell is not taking
> the input.
> 
> I wrote an init.c and opened the ttyCPM0 and tried to read from it,
> but couldn't. I am able to write to ttyCPM0 and see it on the host
> minicom.
> 
> Please some one help me.

Check your pin and clock setup -- perhaps tx is set up correctly but rx
isn't.

-Scott

Re: Problem with Busybox shell

[MohanReddy koppula]

But, if there is any problem with cable I could not have seen any
character in the interrupt routine of the driver. I turned off both
software and hardware flow control as by board doesn't have hardware
flow control. tty_read is called and it hangs at ldisc->read. And I
see that data is put into the tty buffer by the driver. Will there be
any problem with copy_to_user() if there is some problem in the
memory?

Thanks,
Mohan

On Tue, Jan 18, 2011 at 12:55 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
> On Tue, 18 Jan 2011, MohanReddy koppula wrote:
>
>> Hi All,
>>
>> I am working on an MPC885 based custom board. I am able to boot up the
>> linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
>> is not accepting any inputs, I am not able to enter any command, it
>> just hangs there. I am using ttyCPM0 terminal.
>>
>> I suspected if there was any problem in CPM driver interrupts
>> generation and put some printk's in the interrupt handler and could
>> see interrupts are raised and data is read, but shell is not taking
>> the input.
>>
>> I wrote an init.c and opened the ttyCPM0 and tried to read from it,
>> but couldn't. I am able to write to ttyCPM0 and see it on the host
>> minicom.
>>
> if you are using minicom to connect check if you have hardware/software flow
> control turned on - it also could be a cabling problem - had this with the
> beagle board where the tx line was on the wrong pin - so I got output but
> could not get any response to input.
>
> hofrat
>
>

Re: Problem with Busybox shell

[tiejun.chen]

MohanReddy koppula wrote:
> But, if there is any problem with cable I could not have seen any
> character in the interrupt routine of the driver. I turned off both

I suppose the bootloader, i.e u-boot, works well so looks this should not be
issued by the cable at least.

> software and hardware flow control as by board doesn't have hardware
> flow control. tty_read is called and it hangs at ldisc->read. And I

Any panic information? Or any dead lock? Which line in detail?

> see that data is put into the tty buffer by the driver. Will there be
> any problem with copy_to_user() if there is some problem in the
> memory?

Can the serial driver support the poll mode? If so maybe you can take a try to
exclude any interrupt reason.

And even you can remove all codes to initialize the corresponding PIN & CLK
dedicated to the serial port, then try again since the bootloader already did this.

Tiejun

> 
> Thanks,
> Mohan
> 
> On Tue, Jan 18, 2011 at 12:55 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
>> On Tue, 18 Jan 2011, MohanReddy koppula wrote:
>>
>>> Hi All,
>>>
>>> I am working on an MPC885 based custom board. I am able to boot up the
>>> linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
>>> is not accepting any inputs, I am not able to enter any command, it
>>> just hangs there. I am using ttyCPM0 terminal.
>>>
>>> I suspected if there was any problem in CPM driver interrupts
>>> generation and put some printk's in the interrupt handler and could
>>> see interrupts are raised and data is read, but shell is not taking
>>> the input.
>>>
>>> I wrote an init.c and opened the ttyCPM0 and tried to read from it,
>>> but couldn't. I am able to write to ttyCPM0 and see it on the host
>>> minicom.
>>>
>> if you are using minicom to connect check if you have hardware/software flow
>> control turned on - it also could be a cabling problem - had this with the
>> beagle board where the tx line was on the wrong pin - so I got output but
>> could not get any response to input.
>>
>> hofrat
>>
>>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
> 

Re: Problem with Busybox shell

[MohanReddy koppula]

I further debugged and found that flush_to_ldisc() function is not
called which actually wakes up the readers. This is a worker function
and is not being scheduled. I suspected whether timer interrupts are
generated or not. powerpc uses decrementer exceptions as timer
interrupts. I see that timer_interrupt() function in
arch/powerpc/kernel/time.c is not called at all. I printed even
jiffies values and it is not incremented. And I beleivethis makes
scheduler is not scheduling this worker thread.

 I think if flush_to_ldisc is not called nothing can be read from the tty.

Please let me know what could be the reason for timer interrupt being
not called.

Thanks,
Mohan




On Wed, Jan 19, 2011 at 12:37 AM, tiejun.chen <tiejun.chen@windriver.com> wrote:
> MohanReddy koppula wrote:
>> But, if there is any problem with cable I could not have seen any
>> character in the interrupt routine of the driver. I turned off both
>
> I suppose the bootloader, i.e u-boot, works well so looks this should not be
> issued by the cable at least.
>
>> software and hardware flow control as by board doesn't have hardware
>> flow control. tty_read is called and it hangs at ldisc->read. And I
>
> Any panic information? Or any dead lock? Which line in detail?
>
>> see that data is put into the tty buffer by the driver. Will there be
>> any problem with copy_to_user() if there is some problem in the
>> memory?
>
> Can the serial driver support the poll mode? If so maybe you can take a try to
> exclude any interrupt reason.
>
> And even you can remove all codes to initialize the corresponding PIN & CLK
> dedicated to the serial port, then try again since the bootloader already did this.
>
> Tiejun
>
>>
>> Thanks,
>> Mohan
>>
>> On Tue, Jan 18, 2011 at 12:55 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
>>> On Tue, 18 Jan 2011, MohanReddy koppula wrote:
>>>
>>>> Hi All,
>>>>
>>>> I am working on an MPC885 based custom board. I am able to boot up the
>>>> linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
>>>> is not accepting any inputs, I am not able to enter any command, it
>>>> just hangs there. I am using ttyCPM0 terminal.
>>>>
>>>> I suspected if there was any problem in CPM driver interrupts
>>>> generation and put some printk's in the interrupt handler and could
>>>> see interrupts are raised and data is read, but shell is not taking
>>>> the input.
>>>>
>>>> I wrote an init.c and opened the ttyCPM0 and tried to read from it,
>>>> but couldn't. I am able to write to ttyCPM0 and see it on the host
>>>> minicom.
>>>>
>>> if you are using minicom to connect check if you have hardware/software flow
>>> control turned on - it also could be a cabling problem - had this with the
>>> beagle board where the tx line was on the wrong pin - so I got output but
>>> could not get any response to input.
>>>
>>> hofrat
>>>
>>>
>> _______________________________________________
>> Linuxppc-dev mailing list
>> Linuxppc-dev@lists.ozlabs.org
>> https://lists.ozlabs.org/listinfo/linuxppc-dev
>>
>
>

Re: Problem with Busybox shell

[tiejun.chen]

MohanReddy koppula wrote:
> I further debugged and found that flush_to_ldisc() function is not
> called which actually wakes up the readers. This is a worker function
> and is not being scheduled. I suspected whether timer interrupts are
> generated or not. powerpc uses decrementer exceptions as timer
> interrupts. I see that timer_interrupt() function in
> arch/powerpc/kernel/time.c is not called at all. I printed even
> jiffies values and it is not incremented. And I beleivethis makes
> scheduler is not scheduling this worker thread.
> 
>  I think if flush_to_ldisc is not called nothing can be read from the tty.
> 
> Please let me know what could be the reason for timer interrupt being
> not called.

As you know the decrement exception always is invoked by the TB REGs, unless
there is one higher priority exception to block that.

Here I show the jiffies updating path simply as follows (only one simple path,
actually the timer framework should be more complicated.):
-------
DECREMENT Exception
	-> timer_interrupt
		|
		+ evt->event_handler(evt);
			|
			+ tick_handle_periodic()
				|
				+ tick_periodic(cpu);
Then
------
static void tick_periodic(int cpu)
{
        if (tick_do_timer_cpu == cpu) {
                write_seqlock(&xtime_lock);

                /* Keep track of the next tick event */
                tick_next_period = ktime_add(tick_next_period, tick_period);

                do_timer(1);
                write_sequnlock(&xtime_lock);
        }

        update_process_times(user_mode(get_irq_regs()));
        profile_tick(CPU_PROFILING);
}

So if we cannot set/update TB we would have no decrement exception. Or the
kernel is locked/looped somewhere.

Can you track the whole process via print? Maybe you can find out something. And
I'm not familiar with 885, is is SMP?

Tiejun

> 
> Thanks,
> Mohan
> 
> 
> 
> 
> On Wed, Jan 19, 2011 at 12:37 AM, tiejun.chen <tiejun.chen@windriver.com> wrote:
>> MohanReddy koppula wrote:
>>> But, if there is any problem with cable I could not have seen any
>>> character in the interrupt routine of the driver. I turned off both
>> I suppose the bootloader, i.e u-boot, works well so looks this should not be
>> issued by the cable at least.
>>
>>> software and hardware flow control as by board doesn't have hardware
>>> flow control. tty_read is called and it hangs at ldisc->read. And I
>> Any panic information? Or any dead lock? Which line in detail?
>>
>>> see that data is put into the tty buffer by the driver. Will there be
>>> any problem with copy_to_user() if there is some problem in the
>>> memory?
>> Can the serial driver support the poll mode? If so maybe you can take a try to
>> exclude any interrupt reason.
>>
>> And even you can remove all codes to initialize the corresponding PIN & CLK
>> dedicated to the serial port, then try again since the bootloader already did this.
>>
>> Tiejun
>>
>>> Thanks,
>>> Mohan
>>>
>>> On Tue, Jan 18, 2011 at 12:55 PM, Nicholas Mc Guire <der.herr@hofr.at> wrote:
>>>> On Tue, 18 Jan 2011, MohanReddy koppula wrote:
>>>>
>>>>> Hi All,
>>>>>
>>>>> I am working on an MPC885 based custom board. I am able to boot up the
>>>>> linux (linux-2.6.33.7). I could see busybox shell (ash) prompt. But it
>>>>> is not accepting any inputs, I am not able to enter any command, it
>>>>> just hangs there. I am using ttyCPM0 terminal.
>>>>>
>>>>> I suspected if there was any problem in CPM driver interrupts
>>>>> generation and put some printk's in the interrupt handler and could
>>>>> see interrupts are raised and data is read, but shell is not taking
>>>>> the input.
>>>>>
>>>>> I wrote an init.c and opened the ttyCPM0 and tried to read from it,
>>>>> but couldn't. I am able to write to ttyCPM0 and see it on the host
>>>>> minicom.
>>>>>
>>>> if you are using minicom to connect check if you have hardware/software flow
>>>> control turned on - it also could be a cabling problem - had this with the
>>>> beagle board where the tx line was on the wrong pin - so I got output but
>>>> could not get any response to input.
>>>>
>>>> hofrat

Re: Problem with Busybox shell

[Gorelik, Jacob (335F)]

Hi Mohan,

Were you able to fix your problem? I am having the same problem with my boa=
rd. It is PPC750FX with Marvell MV64460.

Jacob=