8266 SMC uart corruption

Rune Torgersen runet at innovsys.com
Wed Feb 9 04:45:44 EST 2005

More Info:
This seems to be related to cpm_uart_stop_tx()
There seems to be an excessive amount of stops and starts going on
In the following, I print an \ for each time stop_tx is called, and a / for start_tx

EXT3-fs: mounted filesystem with ordered data mode.
VFS: Mounted root (ext3 filesystem).
Freeing unused kernel memory: 288k init
\/I\/T\/·\/vers\/i\/on 2\/.\/85 b\/o\/otin\/ /
\/Acti\/v\/atin\/g\/ all\/ \/swap\/ \/file\/s\//par\/t\/itio\/n\/s...\<6>Adding 1028152k swap on /dev/hda2.  Priority:1 extents:1
/       \/[  \/OK\/  ]\/
\/Moun\/t\/ing \/p\/roc \/f\/ile \/s\/yste\/m\/...\/    \/[  \/OK\/  ]\/
\/Moun\/t\/ing \/r\/oot \/f\/ile \/s\/yste\/m\/ in \/r\/ead-\/o\/nly \/m\/ode.\/.\/.\/

And so on.

If I put in a udelay(10000) at the end of cpm_uart_stop_tx, all output prints OK, but slow.

2.6.7 and prior does not use the stop at all form what I can see.

> -----Original Message-----
> From: Rune Torgersen 
> Sent: Tuesday, February 01, 2005 08:42
> To: linuxppc-embedded at ozlabs.org
> Subject: 8266 SMC uart corruption
> Hi
> Has anybordy else seen corruption of the output from SMC1 
> when used as serial console?
> This only occurs in in 2.6.8 and later (when the CPM serial 
> drivers got moved)
> And it only occurs when init is writing to screen. 2.6.7 and 
> earlier works perfectly.
> It happens at all baudrates tested (9600 and 115200)
> Anybody seen something similar and/or have a clue where to 
> start looking for this?
> I have looked at the serial drivers, and cannot find any 
> differences large differences from whenthey still were in 
> arch/ppc/8260_io to the ones in drivers/serial/cpm_uart
> Capture:
> Freeing unused kernel memory: 288k iεt
> I■T: version 2.85 boot∙g
> ...
> I■T Entering runlevel: 3
> These lines are the only ones that get corrupted. All other 
> output (kernel printouts, console and startup scripts) are normal.

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