Hi! I have troubles with my stealth port on a G3-blue. When it runs at
115200
quoted
ifconfig
shows a lot of overruns. At 57600 it works fine, but it's slow :-((
The problem is definitely X. I made a lot of tests: with dma and non-dma
serial driver, X accelerated, non accelerated, X bare.bone (started with
xinit). The problem is X. When X is running the serial ports looses packets
:-((
Am I the only one who is having this problem ??? Why does X cause overruns ??
If you can try 2.2.17pre10ben2 or pre13ben2 (linuxcare linux-pmac-benh) then
you can apply the IRQ latency test and see if it is that which is blocking
you. Scan the dev list for "[ANN} IRQ".
It is possible (there was a discussion in the ANN thread about fb IRQ
blocks) - X may aggravate this.
I have seen 2ms of IRQ blocking on the Lombard (using IDE CDROM) and around
450-750 us of IRQ blocking on my other machines (SCSI). [when heavily
loaded].
The RX buffer in an 85230 (which is actually the chip - IIRC - an enhanced
8530) is 8 characters deep - so any more that about 700 us IRQ block will
cause a drop out at 115200 continuous...
So it looks like music might not be the only pressure to tune the IRQ
latencies :-)
Note that an x86 kernel guru said on the lad list "a well tuned kernel
should not exhibit more than about 60 us worst-case IRQ block"
we have a ways to go to get to that.
Iain.
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The RX buffer in an 85230 (which is actually the chip - IIRC - an enhanced
8530) is 8 characters deep
Ok, this is a news to me. I'm certain that SCC on oldworld pmacs is
85C30. When did the change to 85230 occur? If I remember correctly,
some DMA setup codes in macserial.c need to know about it if it's dealing
with 85230 rather than 85C30.
- so any more that about 700 us IRQ block will
cause a drop out at 115200 continuous...
With DMA, this is a non-issue as far as serial driver is concerned.
Takashi Oe
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The problem is definitely X. I made a lot of tests: with dma and non-dma
serial driver, X accelerated, non accelerated, X bare.bone (started with
xinit). The problem is X. When X is running the serial ports looses packets
:-((
Am I the only one who is having this problem ??? Why does X cause overruns
??
If you can try 2.2.17pre10ben2 or pre13ben2 (linuxcare linux-pmac-benh) then
you can apply the IRQ latency test and see if it is that which is blocking
you. Scan the dev list for "[ANN} IRQ".
I'll try a soon I have a bit of free time...
It is possible (there was a discussion in the ANN thread about fb IRQ
blocks) - X may aggravate this.
I have seen 2ms of IRQ blocking on the Lombard (using IDE CDROM) and around
450-750 us of IRQ blocking on my other machines (SCSI). [when heavily
loaded].
:-6 Why IRQ is kept locked for so much time ?
The RX buffer in an 85230 (which is actually the chip - IIRC - an enhanced
8530) is 8 characters deep - so any more that about 700 us IRQ block will
cause a drop out at 115200 continuous...
On the Amiga I used to rtx stuff at 230K with no problems. It has 1 byte
buffer...
Bye.
Giuliano Pochini ->)|(<- Shiny Corporation {AS6665} ->)|(<-
** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
On the Amiga I used to rtx stuff at 230K with no problems. It has 1 byte
buffer...
Under AmigaOS or under Linux/{m68k,PPC}? :-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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