mmc: sdio: runtime PM and 8686 problems
I've had a play with the nRESET line (as far as I can tell it is the only pin I have access to), and no joy.
Also tried playing about a bit with the CMD sequence, again no joy.
I'm not entirely sure of the CMD sequence. It seems we get:
- CMD52 (x2)
- CMD0
- CMD8 (fails)
- CMD5 (fails)
In the "SDIO Simplified Specification Version 2.00" (https://www.sdcard.org/developers/overview/sdio/sdio_spec/Simplified_SDIO_Card_Spec.pdf) page 6 it seems only a CMD52 should be required to "Re-init IO". Previous thread posts state CMD5 (x2) are required by the 8686, but why CMD0/CMD8?
Incidentally errors only occur after the CMD0, but before the first error we get (i.e. a change of cs from 1 to 0):
"mmc1: clock 400000Hz busmode 2 powermode 2 cs 0 Vdd 20 width 0 timing 0".
Any thoughts?
I think we've probably hit the end of the line here, unless someone else pops up who knows more about the Gumstix (i.e. has access to a schematic) or the W2CBW003 and it's SD8686 internals.
Thanks for the help anyway chaps!
Cheers,
Joe
-----Original Message-----
From: Ohad Ben-Cohen <[email protected]>
To: Joe Woodward <[email protected]>
Cc: Daniel Drake <[email protected]>, [email protected], Chris Ball <[email protected]>
Date: Thu, 1 Dec 2011 10:07:24 +0200
Subject: Re: mmc: sdio: runtime PM and 8686 problems
Quoted 40 lines
Quoted 1 line · Joe Woodward
It seems CMD5 fails (which seems to be what the workarounds were
aiming to fix).
Right; you get a timeout (-110), which means the 8686 didn't send any response.
This is unexpected because the sdio reset (the CMD52 you see before the init sequence) should be enough to reset the device (we confirmed this with the Marvell folks on this list awhile ago).
Quoted 1 line
I'm afraid I may not be of much more use as Gumstix (annoyingly)
don't release schematics of their COMs, so actually probing any signals isn't really possible.
Yes, it makes it difficult to debug.
You can try to verify (in the code) that all the text book prerequisites are there (e.g. all SDIO lines are pulled up and muxed correctly. though since stuff work for you without SDIO runtime PM, I assume these are ok), and maybe even play a bit with stuff like delays, sdio resets and power cycles and see if things change. If you have access to the other inputs of the 8686 (it has several of them which are related to power and resets. Neither me nor Daniel have intimate knowledge about what any of those really do, but you could dig some info from emails send by Marvell folks on this list), then you can also try to play with them and see if things change. With luck, you could learn more about the problem and can hopefully get closer to finding a solution.
It could be great if a solution will be found, but if not, we'll probably have to proceed with the revert...
Good luck!
Ohad.
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