[U-Boot] [PATCH] mmc: fix OCR Polling

[Andrew Gabbasov <andrew_gabbasov@mentor.com>]

Hi Peng,

> From: Peng.Fan at freescale.com (Peng Fan)
> Date: Thu, 19 Mar 2015 16:22:46 +0800
> Subject: [U-Boot] [PATCH] mmc: fix OCR Polling
> 
> If in mmc_send_op_cond, OCR_BUSY is set in CMD1's response, then
> state is transfered to Ready state, and there is no need to send
> CMD1 again. Otherwise following CMD1 will recieve no response, or
> timeour error from driver such as fsl_esdhc.c.
> 
> If not into Ready state in previous CMD1, then continue CMD1 command.
> 
> In mmc_complete_op_cond, we use the value mmc->op_cond_response
> from mmc_send_op_cond, since there should be no CMD1 command between
> mmc_send_op_cond and mmc_complete_op_cond
> 
> Before fixing this, uboot log shows:
> "
> CMD_SEND:0
>                 ARG                      0x00000000
>                 MMC_RSP_NONE
> CMD_SEND:8
>                 ARG                      0x000001AA
>                 MMC_RSP_R1,5,6,7         0x18EC1504
> CMD_SEND:55
>                 ARG                      0x00000000
>                 MMC_RSP_R1,5,6,7         0x18EC1504
> CMD_SEND:0
>                 ARG                      0x00000000
>                 MMC_RSP_NONE
> CMD_SEND:1
>                 ARG                      0x00000000
>                 MMC_RSP_R3,4             0x00FF8080
> CMD_SEND:1
>                 ARG                      0x40300000
>                 MMC_RSP_R3,4             0xC0FF8080 --> Already OCR_BUSY
set
> CMD_SEND:1
>                 ARG                      0x40300000
>                 MMC_RSP_R3,4             0x0096850A --> Failed CMD1
> MMC init failed
> "
> 
> Using this patch, this issue is fixed, emmc can be detected correctly.
> 
> 
> Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
> ---
>  drivers/mmc/mmc.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
> index a13769e..43a9a8a 100644
> --- a/drivers/mmc/mmc.c
> +++ b/drivers/mmc/mmc.c
> @@ -406,14 +406,23 @@ static int mmc_complete_op_cond(struct mmc *mmc)
>  
>      mmc->op_cond_pending = 0;
>      start = get_timer(0);
> -    do {
> +    /*
> +     * If in mmc_send_op_cond, OCR_BUSY is set in CMD1's response, then
> +     * state is transfered to Ready state, and there is no need to
> +     * send CMD1 again. Otherwise following CMD1 will recieve no
response,
> +     * or timeour error from driver such as fsl_esdhc.c.
> +     *
> +     * If not into Ready state in previous CMD1, then continue CMD1
> +     * command.
> +     */
> +    while (!(mmc->op_cond_response & OCR_BUSY)) {
>          err = mmc_send_op_cond_iter(mmc, &cmd, 1);
>          if (err)
>              return err;
>          if (get_timer(start) > timeout)
>              return UNUSABLE_ERR;
>          udelay(100);
> -    } while (!(mmc->op_cond_response & OCR_BUSY));
> +    }
>  
>      if (mmc_host_is_spi(mmc)) { /* read OCR for spi */
>          cmd.cmdidx = MMC_CMD_SPI_READ_OCR;
> -- 
> 1.8.4

After this patch, if the busy flag is indeed already set (so that the loop
body
is not executed), and it is not an SPI case (mmc_host_is_spi(mmc) is false),
the "cmd" structure (which is local to mmc_complete_op_cond() function)
is left uninitialized, and using cmd.response[0] later in the function
becomes
incorrect. And the OCR register value and the high capacity flag may be set
incorrectly.

So, this patch is not enough by itself, it needs to be modified (appended)
in order to get the correct code.

Coincidentally, the same day I submitted a patch series
("[U-Boot] [PATCH 0/6] mmc: Fix OCR polling and splitted initialization"),
that, among other changes, fixes the OCR polling problem too
("[U-Boot] [PATCH 4/6] mmc: Continue polling MMC card for OCR only if it is
still not ready"),
but in a slightly different way, that hopefully doesn't have the mentioned
issue.

Thanks.

Best regards,
Andrew