Re: Problem with Busybox shell

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 [off-list ref] wrote:

MohanReddy koppula wrote:

quoted

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.

quoted

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?

quoted

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

quoted

Thanks,
Mohan

On Tue, Jan 18, 2011 at 12:55 PM, Nicholas Mc Guire [off-list ref] wrote:

quoted

On Tue, 18 Jan 2011, MohanReddy koppula wrote:

quoted

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

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