diff options
Diffstat (limited to 'Documentation/serial/sx.txt')
| -rw-r--r-- | Documentation/serial/sx.txt | 294 |
1 files changed, 0 insertions, 294 deletions
diff --git a/Documentation/serial/sx.txt b/Documentation/serial/sx.txt deleted file mode 100644 index cb4efa0..0000000 --- a/Documentation/serial/sx.txt +++ /dev/null @@ -1,294 +0,0 @@ - - sx.txt -- specialix SX/SI multiport serial driver readme. - - - - Copyright (C) 1997 Roger Wolff (R.E.Wolff@BitWizard.nl) - - Specialix pays for the development and support of this driver. - Please DO contact support@specialix.co.uk if you require - support. - - This driver was developed in the BitWizard linux device - driver service. If you require a linux device driver for your - product, please contact devices@BitWizard.nl for a quote. - - (History) - There used to be an SI driver by Simon Allan. This is a complete - rewrite from scratch. Just a few lines-of-code have been snatched. - - (Sources) - Specialix document number 6210028: SX Host Card and Download Code - Software Functional Specification. - - (Copying) - This program is free software; you can redistribute it and/or - modify it under the terms of the GNU General Public License as - published by the Free Software Foundation; either version 2 of - the License, or (at your option) any later version. - - This program is distributed in the hope that it will be - useful, but WITHOUT ANY WARRANTY; without even the implied - warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR - PURPOSE. See the GNU General Public License for more details. - - You should have received a copy of the GNU General Public - License along with this program; if not, write to the Free - Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, - USA. - - (Addendum) - I'd appreciate it that if you have fixes, that you send them - to me first. - - -Introduction -============ - -This file contains some random information, that I like to have online -instead of in a manual that can get lost. Ever misplace your Linux -kernel sources? And the manual of one of the boards in your computer? - - -Theory of operation -=================== - -An important thing to know is that the driver itself doesn't have the -firmware for the card. This means that you need the separate package -"sx_firmware". For now you can get the source at - - ftp://ftp.bitwizard.nl/specialix/sx_firmware_<version>.tgz - -The firmware load needs a "misc" device, so you'll need to enable the -"Support for user misc device modules" in your kernel configuration. -The misc device needs to be called "/dev/specialix_sxctl". It needs -misc major 10, and minor number 167 (assigned by HPA). The section -on creating device files below also creates this device. - -After loading the sx.o module into your kernel, the driver will report -the number of cards detected, but because it doesn't have any -firmware, it will not be able to determine the number of ports. Only -when you then run "sx_firmware" will the firmware be downloaded and -the rest of the driver initialized. At that time the sx_firmware -program will report the number of ports installed. - -In contrast with many other multi port serial cards, some of the data -structures are only allocated when the card knows the number of ports -that are connected. This means we won't waste memory for 120 port -descriptor structures when you only have 8 ports. If you experience -problems due to this, please report them: I haven't seen any. - - -Interrupts -========== - -A multi port serial card, would generate a horrendous amount of -interrupts if it would interrupt the CPU for every received -character. Even more than 10 years ago, the trick not to use -interrupts but to poll the serial cards was invented. - -The SX card allow us to do this two ways. First the card limits its -own interrupt rate to a rate that won't overwhelm the CPU. Secondly, -we could forget about the cards interrupt completely and use the -internal timer for this purpose. - -Polling the card can take up to a few percent of your CPU. Using the -interrupts would be better if you have most of the ports idle. Using -timer-based polling is better if your card almost always has work to -do. You save the separate interrupt in that case. - -In any case, it doesn't really matter all that much. - -The most common problem with interrupts is that for ISA cards in a PCI -system the BIOS has to be told to configure that interrupt as "legacy -ISA". Otherwise the card can pull on the interrupt line all it wants -but the CPU won't see this. - -If you can't get the interrupt to work, remember that polling mode is -more efficient (provided you actually use the card intensively). - - -Allowed Configurations -====================== - -Some configurations are disallowed. Even though at a glance they might -seem to work, they are known to lockup the bus between the host card -and the device concentrators. You should respect the drivers decision -not to support certain configurations. It's there for a reason. - -Warning: Seriously technical stuff ahead. Executive summary: Don't use -SX cards except configured at a 64k boundary. Skip the next paragraph. - -The SX cards can theoretically be placed at a 32k boundary. So for -instance you can put an SX card at 0xc8000-0xd7fff. This is not a -"recommended configuration". ISA cards have to tell the bus controller -how they like their timing. Due to timing issues they have to do this -based on which 64k window the address falls into. This means that the -32k window below and above the SX card have to use exactly the same -timing as the SX card. That reportedly works for other SX cards. But -you're still left with two useless 32k windows that should not be used -by anybody else. - - -Configuring the driver -====================== - -PCI cards are always detected. The driver auto-probes for ISA cards at -some sensible addresses. Please report if the auto-probe causes trouble -in your system, or when a card isn't detected. - -I'm afraid I haven't implemented "kernel command line parameters" yet. -This means that if the default doesn't work for you, you shouldn't use -the compiled-into-the-kernel version of the driver. Use a module -instead. If you convince me that you need this, I'll make it for -you. Deal? - -I'm afraid that the module parameters are a bit clumsy. If you have a -better idea, please tell me. - -You can specify several parameters: - - sx_poll: number of jiffies between timer-based polls. - - Set this to "0" to disable timer based polls. - Initialization of cards without a working interrupt - will fail. - - Set this to "1" if you want a polling driver. - (on Intel: 100 polls per second). If you don't use - fast baud rates, you might consider a value like "5". - (If you don't know how to do the math, use 1). - - sx_slowpoll: Number of jiffies between timer-based polls. - Set this to "100" to poll once a second. - This should get the card out of a stall if the driver - ever misses an interrupt. I've never seen this happen, - and if it does, that's a bug. Tell me. - - sx_maxints: Number of interrupts to request from the card. - The card normally limits interrupts to about 100 per - second to offload the host CPU. You can increase this - number to reduce latency on the card a little. - Note that if you give a very high number you can overload - your CPU as well as the CPU on the host card. This setting - is inaccurate and not recommended for SI cards (But it - works). - - sx_irqmask: The mask of allowable IRQs to use. I suggest you set - this to 0 (disable IRQs all together) and use polling if - the assignment of IRQs becomes problematic. This is defined - as the sum of (1 << irq) 's that you want to allow. So - sx_irqmask of 8 (1 << 3) specifies that only irq 3 may - be used by the SX driver. If you want to specify to the - driver: "Either irq 11 or 12 is ok for you to use", then - specify (1 << 11) | (1 << 12) = 0x1800 . - - sx_debug: You can enable different sorts of debug traces with this. - At "-1" all debugging traces are active. You'll get several - times more debugging output than you'll get characters - transmitted. - - -Baud rates -========== - -Theoretically new SXDCs should be capable of more than 460k -baud. However the line drivers usually give up before that. Also the -CPU on the card may not be able to handle 8 channels going at full -blast at that speed. Moreover, the buffers are not large enough to -allow operation with 100 interrupts per second. You'll have to realize -that the card has a 256 byte buffer, so you'll have to increase the -number of interrupts per second if you have more than 256*100 bytes -per second to transmit. If you do any performance testing in this -area, I'd be glad to hear from you... - -(Psst Linux users..... I think the Linux driver is more efficient than -the driver for other OSes. If you can and want to benchmark them -against each other, be my guest, and report your findings...... :-) - - -Ports and devices -================= - -Port 0 is the top connector on the module closest to the host -card. Oh, the ports on the SXDCs and TAs are labelled from 1 to 8 -instead of from 0 to 7, as they are numbered by linux. I'm stubborn in -this: I know for sure that I wouldn't be able to calculate which port -is which anymore if I would change that.... - - -Devices: - -You should make the device files as follows: - -#!/bin/sh -# (I recommend that you cut-and-paste this into a file and run that) -cd /dev -t=0 -mknod specialix_sxctl c 10 167 -while [ $t -lt 64 ] - do - echo -n "$t " - mknod ttyX$t c 32 $t - mknod cux$t c 33 $t - t=`expr $t + 1` -done -echo "" -rm /etc/psdevtab -ps > /dev/null - - -This creates 64 devices. If you have more, increase the constant on -the line with "while". The devices start at 0, as is customary on -Linux. Specialix seems to like starting the numbering at 1. - -If your system doesn't come with these devices pre-installed, bug your -linux-vendor about this. They should have these devices -"pre-installed" before the new millennium. The "ps" stuff at the end -is to "tell" ps that the new devices exist. - -Officially the maximum number of cards per computer is 4. This driver -however supports as many cards in one machine as you want. You'll run -out of interrupts after a few, but you can switch to polled operation -then. At about 256 ports (More than 8 cards), we run out of minor -device numbers. Sorry. I suggest you buy a second computer.... (Or -switch to RIO). - ------------------------------------------------------------------------- - - - Fixed bugs and restrictions: - - Hangup processing. - -- Done. - - - the write path in generic_serial (lockup / oops). - -- Done (Ugly: not the way I want it. Copied from serial.c). - - - write buffer isn't flushed at close. - -- Done. I still seem to lose a few chars at close. - Sorry. I think that this is a firmware issue. (-> Specialix) - - - drain hardware before changing termios - - Change debug on the fly. - - ISA free irq -1. (no firmware loaded). - - adding c8000 as a probe address. Added warning. - - Add a RAMtest for the RAM on the card.c - - Crash when opening a port "way" of the number of allowed ports. - (for example opening port 60 when there are only 24 ports attached) - - Sometimes the use-count strays a bit. After a few hours of - testing the use count is sometimes "3". If you are not like - me and can remember what you did to get it that way, I'd - appreciate an Email. Possibly fixed. Tell me if anyone still - sees this. - - TAs don't work right if you don't connect all the modem control - signals. SXDCs do. T225 firmware problem -> Specialix. - (Mostly fixed now, I think. Tell me if you encounter this!) - - Bugs & restrictions: - - - Arbitrary baud rates. Requires firmware update. (-> Specialix) - - - Low latency (mostly firmware, -> Specialix) - - - |
