On Tuesday, September 01, 2015 at 06:22:08 PM, Pantelis Antoniou wrote:
Hi Marek,
Hi!
[...]
So you suggest adding board_mmc_getcd() in several places in the mmc subsystem driver to detect removal of the SD card?
Hmmmm, I'm not sure about this one. Panto ?
I’m fine with this. Perhaps we can avoid spamming this all over the place, and that would be better.
It'd be cool if the MMC subsystem could pull the wp-gpios and cd-gpios from DT though :)
+1
Indeed. I would expect this to be a per-board thing. I would not expect all platforms to provide that capability.
That's right.
Also, where did you find out there is such "cleanup" mechanism please ?
Internally we did some tests with several SD cards. We were stunned when it turned out that for some workloads it took up to 15 seconds to end write operation for small data.
The culprit is the SD Card embedded controller responsible for FTL - flash translation layer. It allows NAND memory on the card to be visible as the block device. More importantly it also takes care of wear leveling and bad block management.
Hence, we don't know when it would start housekeeping operations. We can only poll/wait until this controller finishes it work. The code as it was (with the indefinite loop) was taking this situation into account.
The 1 second timeout is apparently too short and makes using SD card non-deterministic and error prone in u-boot.
Even worse, many devices use SD card as the only storage device.
Yes, horrible.
Good that we have agreed.
Heh :)
Horrible closed source flash management algorithm is horrible, film at 11 :)
It was some seriously repugnant flick ...