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Author Topic: Reliable SD support by disabling highspeed operations  (Read 4857 times)
philipl
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« on: May 26, 2009, 10:50:27 PM »

So, it was obvious in retrospect, given the break down of cards that work vs. cards that didn't work, but disabling highspeed operations (50Mhz vs 25/20Mhz) makes all cards work.

It's a trivial change to make to the kernel source, and I'd recommend it until the Marvell guys can sort out a working fix. I've attached a diff.

I'd recommend that those people providing pre-built kernels apply this patch - it has no real downside for now because the highspeed card is almost certainly not going to work - so low speed operation is better than no operation at all!

* disable_hs.diff (0.61 KB - downloaded 270 times.)
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karurosu
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« Reply #1 on: May 27, 2009, 10:16:40 PM »

Sounds promising, but I can't find the attachment.
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philipl
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« Reply #2 on: May 27, 2009, 10:28:53 PM »

It's listed right there in my post and it's been downloaded a few times. Text is green on black so you might have missed it :-P
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karurosu
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« Reply #3 on: May 28, 2009, 08:19:22 PM »

I just tested it with the card that was giving me trouble (Kingston SDHC 4 gig) and it worked just fine!
COpied around 200 mb of data (quite a good speed) and then played some mp3 of it.

Thanks a lot for sharing
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Beck12
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« Reply #4 on: May 29, 2009, 12:17:00 AM »

Would this solve the -110 errors when using rootfs from the SDHC Card? I'm able to boot the system from the SDHC but when using the system for a while (1 or 2 mins), i get bunch of -110 errors and then system crash. I'm currently testing Transend 4GB SDHC card.
I'm using 2.6.30-rc7 kernel currently and everything else seems to work OK.
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karurosu
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« Reply #5 on: May 29, 2009, 08:24:53 AM »

Yes, it solves the -110 errors while using them, however I am not sure if its ready for use as rootfs, I made a couple of tests, read and write speeds were OK, however once I started putting a bit of a load on it (downloading a torrent file) every program that used the SD started to slow down.
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mossroy
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« Reply #6 on: July 26, 2009, 02:16:36 PM »

I also applied this patch on a 2.6.30.3 mainline kernel and used the plug for a few hours.
It looks like it took rid of the -110 errors : without this patch, it took a few minutes before these errors to show up.

I run a few speed tests on the SDHC, based on http://www.computingplugs.com/index.php/SheevaPlug_Performance
As expected, the read speed is reduced : 9.1 Mb/s.
The write speed doesn't seem to be affected :  7.5 Mb/s

That's great news : my plug is finally stable, and it boots on the SD card.

Anyway, it's a pitty we have to reduce the speed. I hope a better solution will be found
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mossroy
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« Reply #7 on: July 28, 2009, 01:13:09 PM »

The plug is up for more than 2 days... That's great!
Thank a lot philipl for this patch

PS : my SDHC card is a Crucial CT8GBSDHC
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CqCn
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« Reply #8 on: August 26, 2009, 05:46:58 PM »

Hi, I am resurrecting this old thread.  Do not know if this/similar stuff is being disussed in other threads here.  If so kindly point them out to me.

1.  Does anybody know if this patch is in the  2.6.30-rc6 kernel?  Is this something that can be applied it to the image, or does it require any compiling?  If the former, any pointer to a howto is welcome.

2. Has anybody successfully booted (rootfs  on the SDCard) off a Polaroid 4GB SDCard?  I have successfully booted off many 1,2, and 4GB cards from MicroCenter, Kingston, and Patrist fine.  But this card does boot.  I think I could boot off of this before the Alpha-6 upgrade.

It is copy the rootfs from other working cards over to this, and the contents compare correctly.  Just the boot fails, both paperclip reboot and power up start.
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Cordially, CqCn

mossroy
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« Reply #9 on: August 27, 2009, 11:58:27 AM »

1. no, as far as I know, this patch is not included in any official kernel. The main reason is that it's not necessary for every SD card. Applying this patch disables highspeed, even if the SD card would work correctly with it

2. I don't know. I don't have a Polaroid SDCard.

If you need, I have a 2.6.30.4 kernel with this patch, based on the config of http://sheeva.with-linux.com/sheeva/
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CqCn
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« Reply #10 on: August 27, 2009, 04:47:46 PM »

1. no, as far as I know, this patch is not included in any official kernel. The main reason is that it's not necessary for every SD card. Applying this patch disables highspeed, even if the SD card would work correctly with it

2. I don't know. I don't have a Polaroid SDCard.

If you need, I have a 2.6.30.4 kernel with this patch, based on the config of http://sheeva.with-linux.com/sheeva/
  mossroy,  Thank you very much for your offer of the patched kernel.  I would try yours when I am ready to upgrade my kernel.  I am a methodical person, and would do kernel upgrade only at certain quiet periods of my developments Smiley currently I am in the middle of some other stuff.

The Polaroid 4G card which did not boot, now boots with a rootdelay=5 added to my bootargs_root env!!  Also I find that this card has a higher speed in one of my speed tests than the other 'normally working' sdcards I have.

You forgot to confirm:  so the short patch you had has to be applied to the source and rebuilt?  It is not a patch to that can be applied to my -rc6 kernel?  If that is the only change, I am interested in trying to apply it.  There used to binary patched for very small items like these ??
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Cordially, CqCn

mossroy
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« Reply #11 on: August 28, 2009, 10:46:14 AM »

The patch must be applied on the source code, not on the binary. You have the recompile the kernel.
Anyway, cross-compiling the kernel is not very difficult. See http://www.computingplugs.com/index.php/Building_a_custom_kernel
I used the mainline source code, the config and patches of http://sheeva.with-linux.com/sheeva/, added this patch, and cross-compiled.
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CqCn
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« Reply #12 on: August 28, 2009, 04:10:00 PM »

mossroy,  OK, thanks.  This gives me incentive to upgrade the kernel.  In the near future I would first get the standard 30.4, and then will do for the first time compiler setup.

But I have general question about the update --- mainly because of my lack of knowledge of the kernel.  Can the recompile be avoided in a case like this at all?  I would image the kernel does consist of a whole bunch of modules too?  The change you have may not affect more than a couple of modules.  So a module upgrade path a possible way?  Perhasps the kernel currently is binary image only --- and binary update might be needed??
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Cordially, CqCn

mossroy
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« Reply #13 on: August 29, 2009, 12:43:11 AM »

Well, you're right in general.
But in this particular case, if I remember well, the patch affects the uImage binary (i.e. the kernel itself), not the modules.
I'm not 100% sure anyway...
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birdman
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« Reply #14 on: August 30, 2009, 05:28:08 PM »

I'd expect the code to be in the uImage rather than the modules since if it were in the modules you'd have to get it loaded in order to mount to partition on the SD card that contains the modules (if you were running with rootfs on the SD card) which you are trying to load.....
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