Re: [sysvinit-devel] the sysvinit pause

[Yi Qingliang]

Thanks!

So tired... But, maybe you should congratulate me:).
I got the root cause finally, although I still have doubt.

1. same binary (barebox+kernel+rootfs) running well on mini2440

2. I compared the serial related registers in CPU, and found only one 
different:
the register "UCON0"'s bitfield [11:10], ie. clock selection.
on mini2440, it is 10, on my s3c2442, it is 00.
on mini2440, the tty's wait_until_sent will return quickly, not on s3c2442.

on mini2440, the first try in waiting will found there is something not sended, 
the second try will found it cleared.

but on s3c2442, NOT so.


3. check the tty driver, I found in samsung.c, there is one function is 
related with that:
        's3c24xx_serial_setsource'

4. and then found the caller: 's3c24xx_serial_set_termios'. I have added 
printk in it. and the different it is.

5. in 's3c24xx_serial_set_termios', it will find clock in system info,
on mini2440, it found, on my s3c2442, no luck.

6. add printk to print out all clocks. 
on my s3c2442, there is not 'clk_uart_baud[1-3]'

7, I continue search the clock sources, found that in arch/arm/mach-
s3c24xx/clock-s3c2442.c. but it is only registered for s3c2440, not s3c2442.

8. I checked directory mach-s3c24xx, found file 's3c2442.c' had registered some 
clock info for s3c2442, but only camera related.

9. I added register routine in clock-s3c2440.c to register for s3c2442, 
accroding to registering for s3c2440. (dropped camera related because 
s3c2442.c registered that already, but different with s3c2440's)

10. DONE!!!!! the problem freezing 30section missed. then the getty will give 
login prompt without '-i' option.

11. maybe it is done! but I don't know why kernel code have not register uart 
related clock info for s3c2442, and I don't know where I can get the answer.



On Thursday, January 17, 2013 08:52:03 AM Dr. Werner Fink wrote:
> On Thu, Jan 17, 2013 at 08:42:51AM +0000, Yi Qingliang wrote:
> > On Wednesday, January 16, 2013 08:56:17 AM Dr. Werner Fink wrote:
> > > On Wed, Jan 16, 2013 at 10:08:50AM +0000, address@hidden 
wrote:
> > > > On Wednesday, January 16, 2013 09:44:10 AM address@hidden
> > 
> > wrote:
> > > > > On Tuesday, January 15, 2013 04:56:44 PM Dr. Werner Fink wrote:
> > > > > > On Tue, Jan 15, 2013 at 11:11:21PM +0800, Yi Qingliang wrote:
> > > > > > > On Tuesday, January 15, 2013 12:16:46 PM Dr. Werner Fink wrote:
> > > > > > > > On Tue, Jan 15, 2013 at 06:42:26PM +0000,
> > > > > > > > address@hidden
> > > > 
> > > > why the close(fd) freeze for 30seconds?
> > > > is it related with serial setting? or serial driver?
> > > 
> > > That more kernel driver related. Sorry, but I'm not familiar with this
> > > kind
> > > of serial device nor driver :(
> > 
> > which tty the sysvinit will open if the kernel parameter is
> > 'console=ttySAC0"? I debugged the sysvinit, it open the /dev/console, is
> > that normal?
> Yes as /dev/console is the system console and the real devices used for
> the console are handled by the kernel.  Compare with e.g.
> 
>          cat /proc/consoles
> 
> which will list all devices used for the system console[1].  Even printers
> could be used for a channel of the system console.
> 
> 
>     Werner
> 
> [1] https://patchwork.kernel.org/patch/461091/
-- 
Nanjing Jilong
Yi Qingliang
address@hidden