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SubjectRe: [PATCH] mmc: rtsx: fix incorrect last byte in R2 response

On 08/11/2014 09:02 PM, Dan Carpenter wrote:
> On Mon, Aug 11, 2014 at 04:32:16PM +0800, rogerable@realtek.com wrote:
>> From: Roger Tseng <rogerable@realtek.com>
>>
>> Current code erroneously fill the last byte of R2 response with an undefined
>> value. In addition, it is impossible to obtain the real values since the
>> controller actually 'offloads' the last byte(CRC7, end bit) while receiving R2
>> response. This could cause mmc stack to obtain inconsistent CID from the same
>> card after resume and misidentify it as a different card.
>>
>> Fix by assigning a dummy value 0x01 to the last byte of R2 response.
>>
>> Signed-off-by: Roger Tseng <rogerable@realtek.com>
>> ---
>> drivers/mmc/host/rtsx_pci_sdmmc.c | 1 +
>> drivers/mmc/host/rtsx_usb_sdmmc.c | 1 +
>> 2 files changed, 2 insertions(+)
>>
>> diff --git a/drivers/mmc/host/rtsx_pci_sdmmc.c b/drivers/mmc/host/rtsx_pci_sdmmc.c
>> index dfde4a2..54849d8 100644
>> --- a/drivers/mmc/host/rtsx_pci_sdmmc.c
>> +++ b/drivers/mmc/host/rtsx_pci_sdmmc.c
>> @@ -412,6 +412,7 @@ static void sd_send_cmd_get_rsp(struct realtek_pci_sdmmc *host,
>> }
>>
>> if (rsp_type == SD_RSP_TYPE_R2) {
>> + ptr[16] = 1;
>
> Avoid magic numbers like 16 and 0x1.
>
> This is subtle enough that it deserves a comment.
>
> ptr[stat_idx] = 0x1 /* 0x1 chosen randomly */
>
The 0x1 consists of 7-bit dummy zero CRC and stop bit 1, described in SD
card. Anyway, I'll give a comment to this in the next version.
>> for (i = 0; i < 4; i++) {
>> cmd->resp[i] = get_unaligned_be32(ptr + 1 + i * 4);
>> dev_dbg(sdmmc_dev(host), "cmd->resp[%d] = 0x%08x\n",
>
> There are a lot of magic numbers in this function. We could get rid
> of this i < 4 loop but doing:
>
> memcpy(cmd->resp, ptr + 1, resp_len);
>
> Currently we don't use resp_len and the resp_len = 5 assignment is off
> by one... It should be resp_len = 4. This function is quite ugly.

I can remove the unused rsp_len in this function. But I'm afraid the
loop is still required. The destination cmd->resp is cpu-endian, but the
raw response from SD card in the buffer (pointed by ptr) is big-endian.

> regards,
> dan carpenter
>
>
> ------Please consider the environment before printing this e-mail.
> .
>

Best regards,
Roger Tseng


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