Pierre, Thanks for the information. And what I understood from MMCA specification is that - EXT_CSD_REV: Defines the fixed parameters. related to the EXT_CSD, according to its revision. Nothing to do with MMCA specification version or > 4GB card. SO, I need just one more help from you to browse the MMCA specification where it's mentioned that if Card is >4GB then EXT_CSD_REV Revision should be > 2 (Rev 1.2)? And again the fact I mentioned in my previous email that below fact is from Symbian OS too. So please reply sometime to helping me understand better. Thanks & regards, Ghorai -----Original Message----- From: Pierre Ossman [mailto:pierre@xxxxxxxxx] Sent: 2009-09-15 01:22 To: Ghorai, Sukumar Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; Chikkature Rajashekar, Madhusudhan; Benjamin.Telya@xxxxxxxxxxx; drzeus-list@xxxxxxxxx; Pandita, Vikram; Joshi, Rhishi; Sawant, Anand; Raju, Veeramanikandan Subject: Re: EXT_CSD Register : CSD_STRUCTURE vs CSD_CSD_REV On Mon, 14 Sep 2009 20:34:35 +0530 "Ghorai, Sukumar" <s-ghorai@xxxxxx> wrote: > Hello, > > I am working in Linux MMC driver. > Recently I came across one 16GB MMC card where EXT_CSD Register having EXT_CSD_REV[192] field as ZERO, which is valid according to Specification. But card is not working due to following reason - > > 1. As we know there are two fields in Extended CSD Register - CSD_STRUCTURE Version[194] & EXT_CSD_REV Revision [192]. > > > 1. In mmc.c/ mmc_read_ext_csd () > * Implementation expecting EXT_CSD_REV non zero (e.g. >3 in current code) > * I think it could be checking for CSD_STRUCTURE version. > * Because EXT_CSD_REV having Zero is the valid Field. > * This is the way it's done in other OS too. The opposite, it expects the version to be below 3 as those are the only ones it knows about. Checking the CSD version for the EXT_CSD would just be silly. > > > 1. To check the high capacity card. > * We could check in access mode from OCR. This is not in Linux exactly and steps to check the EXT_CSD_REV. > * This is done in some other OS too. > Checking the OCR is insufficient if I remember the spec correctly, so we ignore it completely. The EXT_CSD needs to be correct for high capacity to work anyway. > So do you think we can update the code to check the CSD_STRUCTURE Version? Please let us know your opinion. No, as that would violate the spec and possibly misinterpret some cards as high-capacity. To handle your card you would have to build some kind of quirks system so that the kernel can identify that this card is buggy and compensate for it. Rgds -- -- Pierre Ossman WARNING: This correspondence is being monitored by the Swedish government. Make sure your server uses encryption for SMTP traffic and consider using PGP for end-to-end encryption. -- 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
