Re: [PATCH] mmc: block: Differentiate busy and non-TRAN state

[Ulf Hansson]

On Tue, 6 Jul 2021 at 10:20, Christian Löhle <CLoehle@xxxxxxxxxxxxxx> wrote:
>
> Prevent race condition with ioctl commands
>
> Wait for both, a card no longer signalling busy
> and it being returned back to TRAN state.
> A card not signaling busy does not mean it is
> ready to accept new regular commands.
> Instead for a command to be done it should not only
> no longer signal busy but also return back to TRAN state,
> at least for commands that eventually transition back
> to TRAN. Otherwise the next ioctl command may be rejected
> as the card is still in PROG state after the previous command.
>
> Signed-off-by: Christian Loehle <cloehle@xxxxxxxxxxxxxx>
> ---
>  drivers/mmc/core/block.c | 84 +++++++++++++++++++++++++++++++++++-----
>  include/linux/mmc/mmc.h  |  9 +++--
>  2 files changed, 80 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 88f4c215caa6..dda10ccee37f 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -411,7 +411,32 @@ static int mmc_blk_ioctl_copy_to_user(struct mmc_ioc_cmd __user *ic_ptr,
>         return 0;
>  }
>
> -static int card_busy_detect(struct mmc_card *card, unsigned int timeout_ms,
> +static int is_return_to_tran_cmd(struct mmc_command *cmd)
> +{
> +       /*
> +        * Cards will never return to TRAN after completing
> +        * identification commands or MMC_SEND_STATUS if they are not selected.
> +        */
> +       switch (cmd->opcode) {
> +       case MMC_GO_IDLE_STATE:
> +       case MMC_SEND_OP_COND:
> +       case MMC_ALL_SEND_CID:
> +       case MMC_SET_RELATIVE_ADDR:
> +       case MMC_SET_DSR:
> +       case MMC_SLEEP_AWAKE:
> +       case MMC_SELECT_CARD:
> +       case MMC_SEND_CSD:
> +       case MMC_SEND_CID:
> +       case MMC_SEND_STATUS:
> +       case MMC_GO_INACTIVE_STATE:
> +       case MMC_APP_CMD:
> +               return false;
> +       default:
> +               return true;
> +       }
> +}

What exactly are you trying to do with the user space program through
the mmc ioctl with all these commands? The mmc ioctl interface is not
designed to be used like that.

In principle, it looks like we should support a complete
re-initialization of the card. I am sorry, but no thanks! This doesn't
work, but more importantly, this should be managed solely by the
kernel, in my opinion.

> +
> +static int card_poll_until_tran(struct mmc_card *card, unsigned int timeout_ms,
>                             u32 *resp_errs)
>  {
>         unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
> @@ -433,8 +458,7 @@ static int card_busy_detect(struct mmc_card *card, unsigned int timeout_ms,
>                         *resp_errs |= status;
>
>                 /*
> -                * Timeout if the device never becomes ready for data and never
> -                * leaves the program state.
> +                * Timeout if the device never returns to TRAN state.
>                  */
>                 if (done) {
>                         dev_err(mmc_dev(card->host),
> @@ -442,6 +466,41 @@ static int card_busy_detect(struct mmc_card *card, unsigned int timeout_ms,
>                                  __func__, status);
>                         return -ETIMEDOUT;
>                 }
> +       } while (R1_CURRENT_STATE(status) != R1_STATE_TRAN);
> +
> +       return err;
> +}
> +
> +static int card_busy_detect(struct mmc_card *card, unsigned int timeout_ms,
> +                           u32 *resp_errs)
> +{
> +       unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
> +       int err = 0;
> +       u32 status;
> +
> +       do {
> +               bool done = time_after(jiffies, timeout);
> +
> +               err = __mmc_send_status(card, &status, 5);
> +               if (err) {
> +                       dev_err(mmc_dev(card->host),
> +                               "error %d requesting status\n", err);
> +                       return err;
> +               }
> +
> +               /* Accumulate any response error bits seen */
> +               if (resp_errs)
> +                       *resp_errs |= status;
> +
> +               /*
> +                * Timeout if the device never becomes ready for data.
> +                */
> +               if (done) {
> +                       dev_err(mmc_dev(card->host),
> +                               "Card remained busy! %s status: %#x\n",
> +                                __func__, status);
> +                       return -ETIMEDOUT;
> +               }
>         } while (!mmc_ready_for_data(status));
>
>         return err;
> @@ -596,12 +655,19 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
>
>         if (idata->rpmb || (cmd.flags & MMC_RSP_R1B) == MMC_RSP_R1B) {
>                 /*
> -                * Ensure RPMB/R1B command has completed by polling CMD13
> -                * "Send Status".
> +                * Ensure card is no longer signalling busy by polling CMD13.
>                  */
>                 err = card_busy_detect(card, MMC_BLK_TIMEOUT_MS, NULL);
>         }
>
> +       if (is_return_to_tran_cmd(&cmd)) {
> +               /*
> +                * Ensure card has returned back to TRAN state (e.g. from PROG)
> +                * and is ready to accept a new command.
> +                */
> +               err = card_poll_until_tran(card, MMC_BLK_TIMEOUT_MS, NULL);
> +       }
> +
>         return err;
>  }
>
> @@ -1630,7 +1696,7 @@ static int mmc_blk_fix_state(struct mmc_card *card, struct request *req)
>
>         mmc_blk_send_stop(card, timeout);
>
> -       err = card_busy_detect(card, timeout, NULL);
> +       err = card_poll_until_tran(card, timeout, NULL);
>
>         mmc_retune_release(card->host);
>
> @@ -1662,7 +1728,7 @@ static void mmc_blk_read_single(struct mmc_queue *mq, struct request *req)
>                         goto error_exit;
>
>                 if (!mmc_host_is_spi(host) &&
> -                   !mmc_ready_for_data(status)) {
> +                   !mmc_tran_and_ready_for_data(status)) {
>                         err = mmc_blk_fix_state(card, req);
>                         if (err)
>                                 goto error_exit;
> @@ -1784,7 +1850,7 @@ static void mmc_blk_mq_rw_recovery(struct mmc_queue *mq, struct request *req)
>
>         /* Try to get back to "tran" state */
>         if (!mmc_host_is_spi(mq->card->host) &&
> -           (err || !mmc_ready_for_data(status)))
> +           (err || !mmc_tran_and_ready_for_data(status)))
>                 err = mmc_blk_fix_state(mq->card, req);
>
>         /*
> @@ -1854,7 +1920,7 @@ static int mmc_blk_card_busy(struct mmc_card *card, struct request *req)
>         if (mmc_host_is_spi(card->host) || rq_data_dir(req) == READ)
>                 return 0;
>
> -       err = card_busy_detect(card, MMC_BLK_TIMEOUT_MS, &status);
> +       err = card_poll_until_tran(card, MMC_BLK_TIMEOUT_MS, &status);
>
>         /*
>          * Do not assume data transferred correctly if there are any error bits
> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
> index d9a65c6a8816..9ae27504cbc9 100644
> --- a/include/linux/mmc/mmc.h
> +++ b/include/linux/mmc/mmc.h
> @@ -163,10 +163,11 @@ static inline bool mmc_op_multi(u32 opcode)
>
>  static inline bool mmc_ready_for_data(u32 status)
>  {
> -       /*
> -        * Some cards mishandle the status bits, so make sure to check both the
> -        * busy indication and the card state.
> -        */
> +       return status & R1_READY_FOR_DATA;

mmc_ready_for_data() is also being called from mmc_busy_cb(). The
check for R1_STATE_TRAN is needed there.

> +}
> +
> +static inline bool mmc_tran_and_ready_for_data(u32 status)
> +{
>         return status & R1_READY_FOR_DATA &&
>                R1_CURRENT_STATE(status) == R1_STATE_TRAN;
>  }
> --

Kind regards
Uffe