Re: [PATCH] Recognize CSD structure version 3

[Adrian Hunter <adrian.hunter@nokia.com>]

Kyungmin Park wrote:
> The eMMC spec 4.4 and 4.3 + additional feature chips has CSD structure version 3

That is not exactly correct.  There is no CSD structure version 1.3.  Instead
there are two fields for CSD structure version.  One in CSD and one in Extended CSD.

In CSD there is:

CSD_STRUCTURE [127:126]
Describes the version of the CSD structure.
Table 44 — CSD register structure
CSD_STRUCTURE    CSD Structure Version    Valid for System Specification Version
0                CSD version No.          1.0 Allocated by MMCA
1                CSD version No.          1.1 Allocated by MMCA
2                CSD version No.          1.2 Version 4.1–4.2–4.3
3                Version is coded in the CSD_STRUCTURE byte in the EXT_CSD register

So the 3 does not mean version 1.3 it just means look at Extended CSD instead.
But the Extended CSD field does not define CSD structure version 3 at all.

CSD_STRUCTURE [194]
This field is a continuation of the CSD_STRUCTURE field in the CSD register
Table 78 — CSD register structure
CSD_STRUCTURE    CSD structure version    Valid for System Specification Version
0                CSD version No. 1.0      Allocated by MMCA
1                CSD version No. 1.1      Allocated by MMCA
2                CSD version No. 1.2      Version 4.1–4.2–4.3-4.4
3–255            Reserved for future use

> To probe these chip properly and make it simple.
> it doesn't check CSD structure.
> 
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 89f7a25..9e42bc6 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -118,15 +118,12 @@ static int mmc_decode_csd(struct mmc_card *card)
>  	u32 *resp = card->raw_csd;
>  
>  	/*
> -	 * We only understand CSD structure v1.1 and v1.2.
> +	 * We understand all CSD structure v1.1, v1.2 and v1.3.

This comment is not correct. v1.3 does not exist.

>  	 * v1.2 has extra information in bits 15, 11 and 10.
>  	 */
>  	csd_struct = UNSTUFF_BITS(resp, 126, 2);
> -	if (csd_struct != 1 && csd_struct != 2) {
> -		printk(KERN_ERR "%s: unrecognised CSD structure version %d\n",

I don't agree with removing this validation without a reason.  Instead
extend it to 3.

To support the '3' value properly, the Extended CSD CSD_STRUCTURE
field needs to be validated also i.e. in mmc_read_ext_csd() do
something like:


	u32 *resp = card->raw_csd;

	if (UNSTUFF_BITS(resp, 126, 2) == 3) {
		check ext_csd[194]
	}




> +	printk(KERN_DEBUG "%s: recognised CSD structure version %d\n",
>  			mmc_hostname(card->host), csd_struct);
> -		return -EINVAL;
> -	}
>  
>  	csd->mmca_vsn	 = UNSTUFF_BITS(resp, 122, 4);
>  	m = UNSTUFF_BITS(resp, 115, 4);
> --
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