linux-kernel - Re: [PATCH] mmc: Add delay between CMD6 and CMD13 for Sandisk eMMC cards

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Date:	Sun, 21 Sep 2014 19:48:27 +0200
From:	Pavel Machek <pavel@....cz>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	Jean-Michel Hautbois <jean-michel.hautbois@...alys.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"tgih.jun@...sung.com" <tgih.jun@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Chris Ball <chris@...ntf.net>
Subject: Re: [PATCH] mmc: Add delay between CMD6 and CMD13 for Sandisk eMMC
 cards

On Mon 2014-09-15 19:44:28, Jaehoon Chung wrote:
> On 09/15/2014 07:08 PM, Jean-Michel Hautbois wrote:
> > Hi Jaehoon,
> > 
> >> On 09/09/2014 09:26 PM, Jean-Michel Hautbois wrote:
> >>> Tested on a i.MX6 board, with Sandisk SDIN5D1-2G.
> >>> Without this patch, I/O errors occur.
> >>> This eMMC seems to have a different Manufacturer ID as it reads 0x45
> >>> and not 0x2 as specified in datasheet.
> >>
> >> I think this patch don't merge into mainline.
> >> This is not solution for problem.
> >> you mentioned the below comment, this is workaround.
> > 
> > Yes
> > 
> >>>
> >>> Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@...alys.com>
> >>> ---
> >>>  drivers/mmc/core/mmc_ops.c | 9 +++++++++
> >>>  1 file changed, 9 insertions(+)
> >>>
> >>> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
> >>> index f51b5ba..91babaa 100644
> >>> --- a/drivers/mmc/core/mmc_ops.c
> >>> +++ b/drivers/mmc/core/mmc_ops.c
> >>> @@ -458,6 +458,15 @@ int __mmc_switch(struct mmc_card *card, u8 set, u8 index, u8 value,
> >>>       if (!use_busy_signal)
> >>>               return 0;
> >>>
> >>> +     /* WORKAROUND: for Sandisk eMMC cards, it might need certain delay
> >>> +      * before sending CMD13 after CMD6
> >>> +      * On SDIN5D1-2G MANFID is 0x45 and not 0x2 as specified in datasheet
> >>> +      */
> >>> +     if (card->cid.manfid == CID_MANFID_SANDISK ||
> >>> +             card->cid.manfid == 0x45) {
> >>> +             msleep(1);
> >>> +     }
> >>
> >> If it's a general problem of Sandisk SDIN5D1-2G,
> >> I think you need to verify this problem. And can you use the MMC_FIXUP() and QUIRK?
> > 
> > Well, this is difficult to verify, I know that on all my SDIN5D1-2G I
> > have this MANFID different from what is defined by CID_MANFID_SANDISK.
> > How should I use MMC_FIXUP ? Like this ?
> 
> I think you need to explain why delay is need.
> i didn't have same card, but it might be your host controller or other problem. 

Datasheet says it is needed, so we need to do the delay.

Adding pointer to the datasheet (page, chapter) to the comment might be good idea.


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