linux-kernel - Re: [PATCH] mmc: core: Remove FW revision from CID check

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Message-ID: <ff06bd46-bf43-d2dc-751f-47f41ccc1821@intel.com>
Date:   Thu, 20 Jul 2023 09:44:56 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Wenchao Chen <wenchao.chen666@...il.com>
Cc:     Wenchao Chen <wenchao.chen@...soc.com>, ulf.hansson@...aro.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhenxiong.lai@...soc.com, chunyan.zhang@...soc.com,
        yuelin.tang@...soc.com
Subject: Re: [PATCH] mmc: core: Remove FW revision from CID check

On 19/07/23 05:46, Wenchao Chen wrote:
> On Tue, Jul 18, 2023 at 2:13 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> On 18/07/23 04:15, Wenchao Chen wrote:
>>> When the card is reset, mmc_card_init() will check if this
>>> card is the previous card by comparing the CID.
>>>
>>> If the firmware is upgraded, the product version may change,
>>> so we remove the product version from the CID check.
>>
>> What is the use-case for this?  I would have thought it is safer
>> not to assume anything about the card after the firmware has been
>> upgraded.
>>
> Hi adrian
>     Understood, but we have case:
>     1.Before the firmware upgrade
>         [T5745@C0] mmc0 oldcard raw->cid[2]: 32691160, raw->cid[3]: d9241800
>         PRV=69
>     2.After the firmware upgrade
>         [T5745@C0] mmc0 cid[2]: 32011160 cid[3]: d9241800
>         PRV=01
>     If the PRV is not excluded in the CID check, then the mmc
> initialization will fail after the mmc reset.
>     In addition, CRC is excluded because some controllers support
> SDHCI_QUIRK2_RSP_136_HAS_CRC.

I do not know what others are doing in this regard, nor what
circumstances are leading to the re-initialization.

Presumably a clean re-initialization could be done by
unbinding and rebinding the host controller.

> 
>>>
>>> Signed-off-by: Wenchao Chen <wenchao.chen@...soc.com>
>>> ---
>>>  drivers/mmc/core/mmc.c | 18 +++++++++++++++++-
>>>  1 file changed, 17 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>> index 89cd48fcec79..32a73378d5c3 100644
>>> --- a/drivers/mmc/core/mmc.c
>>> +++ b/drivers/mmc/core/mmc.c
>>> @@ -32,6 +32,9 @@
>>>  #define MIN_CACHE_EN_TIMEOUT_MS 1600
>>>  #define CACHE_FLUSH_TIMEOUT_MS 30000 /* 30s */
>>>
>>> +#define MMC_CID_PRV_MASK GENMASK(23, 16)
>>> +#define MMC_CID_CRC_MASK GENMASK(7, 0)
>>> +
>>>  static const unsigned int tran_exp[] = {
>>>       10000,          100000,         1000000,        10000000,
>>>       0,              0,              0,              0
>>> @@ -126,6 +129,19 @@ static int mmc_decode_cid(struct mmc_card *card)
>>>       return 0;
>>>  }
>>>
>>> +static int mmc_check_cid(u32 *cid, u32 *raw_cid)
>>> +{
>>> +     /*
>>> +      * When comparing CID, we need to remove the product
>>> +      * version (Field PRV, offset 55:48) and CRC. Because
>>> +      * the product version will change when the firmware
>>> +      * is upgraded. Also, the new CRC is different.
>>> +      */
>>> +     return cid[0] != raw_cid[0] || cid[1] != raw_cid[1] ||
>>> +             (cid[2] & ~MMC_CID_PRV_MASK) != (raw_cid[2] & ~MMC_CID_PRV_MASK) ||
>>> +             (cid[3] & ~MMC_CID_CRC_MASK) != (raw_cid[3] & ~MMC_CID_CRC_MASK);
>>> +}
>>> +
>>>  static void mmc_set_erase_size(struct mmc_card *card)
>>>  {
>>>       if (card->ext_csd.erase_group_def & 1)
>>> @@ -1640,7 +1656,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>>>               goto err;
>>>
>>>       if (oldcard) {
>>> -             if (memcmp(cid, oldcard->raw_cid, sizeof(cid)) != 0) {
>>> +             if (mmc_check_cid(cid, oldcard->raw_cid)) {
>>>                       pr_debug("%s: Perhaps the card was replaced\n",
>>>                               mmc_hostname(host));
>>>                       err = -ENOENT;
>>