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

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Date:	Mon, 15 Sep 2014 12:53:55 +0200
From:	Jean-Michel Hautbois <jean-michel.hautbois@...alys.com>
To:	Jaehoon Chung <jh80.chung@...sung.com>
Cc:	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

2014-09-15 12:44 GMT+02:00 Jaehoon Chung <jh80.chung@...sung.com>:
> 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.

Well, I don't know why it is needed, this is undocumented, nothing in
datasheet explains anything about this.

JM
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