On 17/04/17 03:36, John Ewalt wrote: > Hi all, > > I am not sure if this is the right way to ask a question about SD cards, so > please correct me as I am new to Linux kernel development. > > I am currently working with a Intel Joule SOM and development board (Broxton > M core) and when I insert the SD card, it is recognized as a SDR104 UHS-I > card. Since this host has the MMC_CAP_AGGRESSIVE_PM bit set, it is > suspended. That all works as expected. When the card is resumed, the OCR > is read expecting bit 24 (switch to 1.8 V accepted (S18A)) to be set, but it > is clear as the card is still at 1.8v signaling since it was never powered > down during the suspend. I would expect the power to go off. AFAICS there is ASL in the host controllers _PS3 method to tell the PMIC to do that. > > I see 3 ways to solve this problem: > First, power down the card during suspend. I think this is the intended > behavior but there is no power manager registered to this host (as compiled) > and I'm not sure how to add one, let alone the hardware changes necessary to > implement the powering down of the sd card. > > Second, don't suspend (I have tested this and it works as the card is not > suspended) > > Third, the host could remember that the card was at 1.8v signaling and if it > will not "switch" to 1.8v, assume it is at 1.8v and go through the uhs_setup > anyway. I have tried this too and it works for UHS cards, but I doubt it > would be the right change. > > > I would appreciate any help or direction anyone can provide as I would > really like to use my fast card at the full data rates. I am currently > setup to test any suggestions you have. > > Thank you all, > > -John > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
