USB - the Elephant in our Room


 
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by gsh » Sun Aug 05, 2012 10:54 am
Update on current progress...

I've had a little while to understand what is going wrong with the USB and traced it back to a problem with poor interrupt latency in the kernel. This is causing the split transactions to be delayed beyond a 1ms frame which in turn means that the hub is dropping the packets it stores.

To resolve this I've got two methods:

1) reduce latency, this has already been significantly reduced using a patch already found by one of the other kernel contributors. This was holding a spin lock for long periods of time in the SDHCI driver. Unfortunately the current fix is not suitable because it could do with more work.

2) Implement split transaction scheduling in the FIQ. Currently I've got a patch that implements a FIQ to reduce the 8000 interrupts per second (proper IRQ interrupts) to 800. Since this is not affected by the spinlocks it gives us a very low latency point that we can use to service the split transactions with very low latency. Unfortunately its a hard solution and likely subject to considerable tail of bugs !

So overall yes I'm still working on it but the timeline has been pushed out for another week

Sorry

Gordon
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by obcd » Sun Aug 05, 2012 11:19 am
Gordon,

good to hear you are making progress. It's probably causing stress if you visit the forum...

I doubt the Pi would kill an usb stick or an usb harddrive.
I assume you could kill an usb stick by constantly writing to it, as the number of erase/write cycles of a flash device are limited. I would try a program like winhex and see if that is still able to see the stick. Sometimes clearing the first sector also helps for a fresh restart. (winhex can do that for you)
Windows won't create a drive letter for the stick if it can't find a known partition on it, and most programs access a partition by it's drive letter. In case of the harddisk, a diagnostic program from the manufacturer might show what went wrong.
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by zardoz99 » Sun Aug 05, 2012 12:38 pm
As I stated, the USB sticks were new. The stick now has a completely different LED flash sequence to the working one and enumerates but with no storage visible. No I/O to it is possible.
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by lb » Sun Aug 05, 2012 1:10 pm
Theq FIQ solution seems to be more worthwile. There are other possible sources of interrupt latency than the SDHCI driver, and reducing IRQ overhead is a good thing, too.
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by sulge » Wed Aug 08, 2012 10:30 am
Because of problems with the USB RPi is useless for me. So, how can I recover my money?
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by jamesh » Wed Aug 08, 2012 11:23 am
sulge wrote:Because of problems with the USB RPi is useless for me. So, how can I recover my money?


What specifically is the problem - lots of people are not having problems that affect general usage.

Alternatively, Ebay would be a good start if you want to sell, and there is someone wanting to buy one in the sales section.
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by sulge » Wed Aug 08, 2012 11:36 am
There is not possible to run 5 USB<->Serial cables. This is problem with drivers. NOT with powered USB HUB. I wasted money for several powered hubs. Because I thought of maybe one of them will be working.
How it was tested at all and allowed to be sold!!!!!!!!????????????
And when you finally going to update this driver????????????
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by jamesh » Wed Aug 08, 2012 11:44 am
sulge wrote:There is not possible to run 5 USB<->Serial cables. This is problem with drivers. NOT with powered USB HUB. I wasted money for several powered hubs. Because I thought of maybe one of them will be working.
How it was tested at all and allowed to be sold!!!!!!!!????????????
And when you finally going to update this driver????????????


It's obviously not suitable, I suggest you sell it on Ebay. You should make most of your Pi money back.

The driver will be updated when it's fixed. At the moment its being worked on. Testing during development didn't show problems, but then, it's impossible to test everything, and 5 USB->serial cables was certainly not tested - it's an unusual combination for the intended purpose of the device..
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by sulge » Wed Aug 08, 2012 12:43 pm
Other users report problems with keyboard, with WiFi dongle and others USB devices. Is it also an unusual combination for the intended purpose of the device?
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by rspitz » Wed Aug 08, 2012 12:44 pm
jamesh wrote: [...] it's impossible to test everything, and 5 USB->serial cables was certainly not tested - it's an unusual combination for the intended purpose of the device..

I beg to differ. Any serious product design has to take into account the so called "intended misuse", meaning that you must foresee real-world scenarios where people do things with your product outside of the intended purpose.

Example: The intended purpose of a wall-mounted radiator is to heat the room. One "intended misuse" for this product is that people will sit or lean on it, so the wall mount must be designed to bear that load.

Given the hype that has been built around the RPi in the geek universe, using it for all kinds of "cool" and out-of-the-way applications which are also heavily publicized on the RPi home page, I'd expect at least some word of caution in a similarly prominent fashion that the product is suffering from some serious, er..., let's call them "teething problems".

After my own sobering and not quite uncostly experiences, I am willing to patiently wait for the dedicated volunteers to analyze the USB problems and come up with a solution. I don't have any qualifications that could help in the effort, so my hat's off to Gordon and others who are working on this. However, if the RPi were a purely commercial product by a profit-oriented company, I'd already returned it for a full refund.
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by sulge » Wed Aug 08, 2012 12:50 pm
@jamesh
It seems to me that this is a huge problem. Why Pi did not officially inform the potential buyers? For example here: http://www.raspberrypi.org/ ???
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by PaulCheffus » Wed Aug 08, 2012 1:38 pm
sulge wrote:@jamesh
It seems to me that this is a huge problem. Why Pi did not officially inform the potential buyers? For example here: http://www.raspberrypi.org/ ???


Hi

To put things in perspective this was supposed to be the development release in readiness for the educational one later in the year. If it won't do what you want then as I see it you have two choices, either wait or sell it.

I have a few issues with the USB but they are not in anyway stopping me from using my Pi to experiment with and to learn Linux (not something I would attempt on my home PC).

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by jamesh » Wed Aug 08, 2012 1:48 pm
rspitz wrote:
jamesh wrote: [...] it's impossible to test everything, and 5 USB->serial cables was certainly not tested - it's an unusual combination for the intended purpose of the device..

I beg to differ. Any serious product design has to take into account the so called "intended misuse", meaning that you must foresee real-world scenarios where people do things with your product outside of the intended purpose.

Example: The intended purpose of a wall-mounted radiator is to heat the room. One "intended misuse" for this product is that people will sit or lean on it, so the wall mount must be designed to bear that load.

Given the hype that has been built around the RPi in the geek universe, using it for all kinds of "cool" and out-of-the-way applications which are also heavily publicized on the RPi home page, I'd expect at least some word of caution in a similarly prominent fashion that the product is suffering from some serious, er..., let's call them "teething problems".

After my own sobering and not quite uncostly experiences, I am willing to patiently wait for the dedicated volunteers to analyze the USB problems and come up with a solution. I don't have any qualifications that could help in the effort, so my hat's off to Gordon and others who are working on this. However, if the RPi were a purely commercial product by a profit-oriented company, I'd already returned it for a full refund.


Are you aware how many different products there are out there that could be plugged in? Millions. How could any company, never mind one with no employees test ALL of those, plus various combinations. Not possible. Your wall mounted radiator example is not valid in this case, it's an overly simple case. Mounting brackets are standardised and are simple to test. In the case here, someone is trying to plug in 5 serial/USB adapters. That's a very unusual use case, and akin to someone having to design a wall bracket to support radiators and Terry Waite. One of the reasons versions of windows take so long to release is due to all the testing they have to do to ensure as much as possible works, and even then you get something like Vista, where loads of peripherals failed to work out of the box.
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by jamesh » Wed Aug 08, 2012 1:50 pm
sulge wrote:@jamesh
It seems to me that this is a huge problem. Why Pi did not officially inform the potential buyers? For example here: http://www.raspberrypi.org/ ???


Because we didn't know about it. It hadn't shown up in testing.
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by Jim JKla » Wed Aug 08, 2012 2:06 pm
If you buy a product thats so new it does not have a case and you expect all the bugs to be ironed out of an operating system thats still in development I would say your expectations have to be unrealistic.

I bought my RPi so I could be part of that vanguard of development if you are not happy to be part of it there are people who want a Pi happy to be part of the queue and I am sure one of those would take it off your hands.
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by jeffhaddow » Wed Aug 08, 2012 2:40 pm
@ rspitz and @ sulge

I agree with Jim JKla that you are a but unrealistic to expect the Raspberry Pi to be an all singing all dancing every thing sorted package, when it is a curcuit board.

I have this particular elephant in my room. I currently can only use the RPi with a keyboard and mouse attached (anything else crashes the internet connection). But considering the story that I've been following, particularly about the testing that had to be completed before they went on general sale, I undersand that it is a priveledge to be part of the general testing of the RPi on the open market.

Meanwhile I am learning a lot about operating a lynux computer and find the experience so much more illuminating than the "Locked Box" philosophy of the majority of today's PCs.

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by sulge » Wed Aug 08, 2012 3:26 pm
jamesh wrote:
sulge wrote:@jamesh
It seems to me that this is a huge problem. Why Pi did not officially inform the potential buyers? For example here: http://www.raspberrypi.org/ ???


Because we didn't know about it. It hadn't shown up in testing.


But now you know and still do not inform!!!!!!!


Jim JKla wrote:If you buy a product thats so new it does not have a case and you expect all the bugs to be ironed out of an operating system thats still in development I would say your expectations have to be unrealistic.

I bought my RPi so I could be part of that vanguard of development if you are not happy to be part of it there are people who want a Pi happy to be part of the queue and I am sure one of those would take it off your hands.


Eeeeeeeeee... So you think that the connect several USB devices and test them, before selling RPi was too much?
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by RaTTuS » Wed Aug 08, 2012 3:35 pm
sulge wrote:Eeeeeeeeee... So you think that the connect several USB devices and test them, before selling RPi was too much?

stop digging....
I've connected a lot of stuff to my RPi ,
some of which work and others don't
not all will have been tested by the foundation , and even if they had 100% sure they did not have the linux distribution they have now.
so things move on.

if you update
http://elinux.org/RPi_VerifiedPeripherals
then others will know that your config won't work
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by jamesh » Wed Aug 08, 2012 3:40 pm
sulge wrote:
jamesh wrote:
sulge wrote:@jamesh
It seems to me that this is a huge problem. Why Pi did not officially inform the potential buyers? For example here: http://www.raspberrypi.org/ ???


Because we didn't know about it. It hadn't shown up in testing.


But now you know and still do not inform!!!!!!!


Jim JKla wrote:If you buy a product thats so new it does not have a case and you expect all the bugs to be ironed out of an operating system thats still in development I would say your expectations have to be unrealistic.

I bought my RPi so I could be part of that vanguard of development if you are not happy to be part of it there are people who want a Pi happy to be part of the queue and I am sure one of those would take it off your hands.


Eeeeeeeeee... So you think that the connect several USB devices and test them, before selling RPi was too much?


Your auto repeat on your keyboard appears not to be working correctly - using a Raspi? ;-)

Anyway, there are problems with some devices on some boards - it depends on the devices, it's not just quantity - most boards and devices appears to work pretty well. The improvements to the driver are getting there.

Meanwhile - calm down. On the whole, it's not the end of the world. You could be trying to get you board working in Syria, in which case USB would be the least of your problems.
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by chrisw2 » Wed Aug 08, 2012 4:20 pm
jamesh wrote:... and akin to someone having to design a wall bracket to support radiators and Terry Waite. ...

Terry Waite? the guy held hostage? was he chained to a radiator? Or is there another Terry Waite who breaks radiator brackets? :)
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by RaTTuS » Wed Aug 08, 2012 4:23 pm
chrisw2 wrote:
jamesh wrote:... and akin to someone having to design a wall bracket to support radiators and Terry Waite. ...

Terry Waite? the guy held hostage? was he chained to a radiator? Or is there another Terry Waite who breaks radiator brackets? :)

yes
http://www.newsbiscuit.com/2007/12/07/t ... iator-261/
http://www.bbc.co.uk/worldservice/histo ... ages.shtml
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by sulge » Wed Aug 08, 2012 4:25 pm
Once again:
But now you know about USB driver problems and still do not inform!

This is not "improvements" the drivers has many bugs this is not only RPi problems, but each which use this driver.

Even Linux experts think that this is not a trivial issue! So please inform potential buyers!!!!
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by RaTTuS » Wed Aug 08, 2012 4:29 pm
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by Jim JKla » Wed Aug 08, 2012 4:31 pm
sulge wrote:
Jim JKla wrote:If you buy a product thats so new it does not have a case and you expect all the bugs to be ironed out of an operating system thats still in development I would say your expectations have to be unrealistic.

I bought my RPi so I could be part of that vanguard of development if you are not happy to be part of it there are people who want a Pi happy to be part of the queue and I am sure one of those would take it off your hands.


Eeeeeeeeee... So you think that the connect several USB devices and test them, before selling RPi was too much?


They did connect several but which several? I have I somewhere in the region of 40 USB devices in my house, some of them don't work with Microsoft Products some of them don't work with Linux Ubuntu.

None will work with my Domain 4000 Ageis workstation, my PPC1640 Amstrad lugable, My Commedore Pet or my Osbourne and some of those the manufacturers no longer exist.

There is a list of stuff that they know works but the Operating System is a moveable feast something that you don't have a remote hope of knowing at the testing stage.

The phase we are still in

To be honest I don't care if the RPi only worked with a Keyboard Mouse and Monitor. I paid three times more for a 16k Sinclair Spectrum and not in real terms it was £109 out of the box ok It did come with a keyboard (rubber) a PSU and cables to connect to a TV and cassette recorder oh yes it came with a ring bound manual and a cassette tape.

By the way the Spectrum did not work with all cassette players at the time (cheaper ones worked best).

Even as it stands bare board the I get more functionality and quality from a Raspberry Pi.

I cannot help but get the feeling your behaving like a spoilt brat thats been presented with the wrong brand of (insert product here).

Yes the USB needs work it is an Elephant in the room we (NOTE WE) need to address and it is in OUR room.

I have to say If you do not like the rules as they stand please do not complain here, because we are busy trying to fix things so that when the real target audience (The School Children) start using the RPi to learn. They get a stable product where the grown ups have sorted out the major bugs. ;)

Please stop throwing your toys out of the pram. We have work to do....

(Sorry Rant over)
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by El_Presidente » Wed Aug 08, 2012 5:18 pm
Jim JKla wrote:Please stop throwing your toys out of the pram. We have work to do....


Well put +1
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