Re: [PATCH] mmc: dw_mmc: Remove old card detect infrastructure

[Alim Akhtar]

Hi Doug,

On Tue, Oct 14, 2014 at 10:03 PM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote:
> The dw_mmc driver had a bunch of code that ran whenever a card was
> ejected and inserted.  However, this code was old and crufty and
> should be removed.  Some evidence that it's really not needed:
>
> 1. Is is supposed to be legal to use 'cd-gpio' on dw_mmc instead of
>    using the built-in card detect mechanism.  The 'cd-gpio' code
>    doesn't run any of the crufty old code but yet still works.
>
> 2. While looking at this, I realized that my old change (369ac86 mmc:
>    dw_mmc: don't queue up a card detect at slot startup) actually
>    castrated the old code a little bit already and nobody noticed.
>    Specifically "last_detect_state" was left as 0 at bootup.  That
>    means that on the first card removal none of the crufty code ran.
>
Yes, right most of these codes are _almost_ never call. But I see
dw_mci_reset() being called on card removal (after first
insert/removal).
I tested this on exynos5800 and this looks working fine. We need to
test once cross suspend/resume as well.
And as Jaehoon pointed out,probably lets look in TRM if there are some
recommended  steps for cd-detect.
Otherwise this looks good to me.

> 3. I can run "while true; do dd if=/dev/mmcblk1 of=/dev/null; done"
>    while ejecting and inserting an SD Card and the world doesn't
>    explode.
>
> If some of the crufty old code is actually needed, we should justify
> it and also put it in some place where it will be run even with
> "cd-gpio".
>
> Note that in my case I'm using the "cd-gpio" mechanism but for various
> reasons the hardware triggers a dw_mmc "card detect" at bootup.  That
> was actually causing a real bug.  The card detect workqueue was
> running while the system was trying to enumerate the card.  The
> "present != slot->last_detect_state" triggered and we were doing all
> kinds of crazy stuff and messing up enumeration.  The new mechanism of
> just asking the core to check the card is much safer and then the
> bogus interrupt doesn't hurt.
>
> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> ---
>  drivers/mmc/host/dw_mmc.c  | 121 ++++++++-------------------------------------
>  drivers/mmc/host/dw_mmc.h  |   2 -
>  include/linux/mmc/dw_mmc.h |   2 -
>  3 files changed, 20 insertions(+), 105 deletions(-)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 69f0cc6..6a86495 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -34,7 +34,6 @@
>  #include <linux/mmc/dw_mmc.h>
>  #include <linux/bitops.h>
>  #include <linux/regulator/consumer.h>
> -#include <linux/workqueue.h>
>  #include <linux/of.h>
>  #include <linux/of_gpio.h>
>  #include <linux/mmc/slot-gpio.h>
> @@ -1954,6 +1953,23 @@ static void dw_mci_cmd_interrupt(struct dw_mci *host, u32 status)
>         tasklet_schedule(&host->tasklet);
>  }
>
> +static void dw_mci_handle_cd(struct dw_mci *host)
> +{
> +       int i;
> +
> +       for (i = 0; i < host->num_slots; i++) {
> +               struct dw_mci_slot *slot = host->slot[i];
> +
> +               if (!slot)
> +                       continue;
> +
> +               if (slot->mmc->ops->card_event)
> +                       slot->mmc->ops->card_event(slot->mmc);
> +               mmc_detect_change(slot->mmc,
> +                       msecs_to_jiffies(host->pdata->detect_delay_ms));
> +       }
> +}
> +
>  static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
>  {
>         struct dw_mci *host = dev_id;
> @@ -2029,7 +2045,7 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
>
>                 if (pending & SDMMC_INT_CD) {
>                         mci_writel(host, RINTSTS, SDMMC_INT_CD);
> -                       queue_work(host->card_workqueue, &host->card_work);
> +                       dw_mci_handle_cd(host);
>                 }
>
>                 /* Handle SDIO Interrupts */
> @@ -2056,88 +2072,6 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
>         return IRQ_HANDLED;
>  }
>
> -static void dw_mci_work_routine_card(struct work_struct *work)
> -{
> -       struct dw_mci *host = container_of(work, struct dw_mci, card_work);
> -       int i;
> -
> -       for (i = 0; i < host->num_slots; i++) {
> -               struct dw_mci_slot *slot = host->slot[i];
> -               struct mmc_host *mmc = slot->mmc;
> -               struct mmc_request *mrq;
> -               int present;
> -
> -               present = dw_mci_get_cd(mmc);
> -               while (present != slot->last_detect_state) {
> -                       dev_dbg(&slot->mmc->class_dev, "card %s\n",
> -                               present ? "inserted" : "removed");
> -
> -                       spin_lock_bh(&host->lock);
> -
> -                       /* Card change detected */
> -                       slot->last_detect_state = present;
> -
> -                       /* Clean up queue if present */
> -                       mrq = slot->mrq;
> -                       if (mrq) {
> -                               if (mrq == host->mrq) {
> -                                       host->data = NULL;
> -                                       host->cmd = NULL;
> -
> -                                       switch (host->state) {
> -                                       case STATE_IDLE:
> -                                       case STATE_WAITING_CMD11_DONE:
> -                                               break;
> -                                       case STATE_SENDING_CMD11:
> -                                       case STATE_SENDING_CMD:
> -                                               mrq->cmd->error = -ENOMEDIUM;
> -                                               if (!mrq->data)
> -                                                       break;
> -                                               /* fall through */
> -                                       case STATE_SENDING_DATA:
> -                                               mrq->data->error = -ENOMEDIUM;
> -                                               dw_mci_stop_dma(host);
> -                                               break;
> -                                       case STATE_DATA_BUSY:
> -                                       case STATE_DATA_ERROR:
> -                                               if (mrq->data->error == -EINPROGRESS)
> -                                                       mrq->data->error = -ENOMEDIUM;
> -                                               /* fall through */
> -                                       case STATE_SENDING_STOP:
> -                                               if (mrq->stop)
> -                                                       mrq->stop->error = -ENOMEDIUM;
> -                                               break;
> -                                       }
> -
> -                                       dw_mci_request_end(host, mrq);
> -                               } else {
> -                                       list_del(&slot->queue_node);
> -                                       mrq->cmd->error = -ENOMEDIUM;
> -                                       if (mrq->data)
> -                                               mrq->data->error = -ENOMEDIUM;
> -                                       if (mrq->stop)
> -                                               mrq->stop->error = -ENOMEDIUM;
> -
> -                                       spin_unlock(&host->lock);
> -                                       mmc_request_done(slot->mmc, mrq);
> -                                       spin_lock(&host->lock);
> -                               }
> -                       }
> -
> -                       /* Power down slot */
> -                       if (present == 0)
> -                               dw_mci_reset(host);
> -
> -                       spin_unlock_bh(&host->lock);
> -
> -                       present = dw_mci_get_cd(mmc);
> -               }
> -
> -               mmc_detect_change(slot->mmc,
> -                       msecs_to_jiffies(host->pdata->detect_delay_ms));
> -       }
> -}
> -
>  #ifdef CONFIG_OF
>  /* given a slot id, find out the device node representing that slot */
>  static struct device_node *dw_mci_of_find_slot_node(struct device *dev, u8 slot)
> @@ -2289,9 +2223,6 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
>         dw_mci_init_debugfs(slot);
>  #endif
>
> -       /* Card initially undetected */
> -       slot->last_detect_state = 0;
> -
>         return 0;
>
>  err_host_allocated:
> @@ -2672,17 +2603,10 @@ int dw_mci_probe(struct dw_mci *host)
>                 host->data_offset = DATA_240A_OFFSET;
>
>         tasklet_init(&host->tasklet, dw_mci_tasklet_func, (unsigned long)host);
> -       host->card_workqueue = alloc_workqueue("dw-mci-card",
> -                       WQ_MEM_RECLAIM, 1);
> -       if (!host->card_workqueue) {
> -               ret = -ENOMEM;
> -               goto err_dmaunmap;
> -       }
> -       INIT_WORK(&host->card_work, dw_mci_work_routine_card);
>         ret = devm_request_irq(host->dev, host->irq, dw_mci_interrupt,
>                                host->irq_flags, "dw-mci", host);
>         if (ret)
> -               goto err_workqueue;
> +               goto err_dmaunmap;
>
>         if (host->pdata->num_slots)
>                 host->num_slots = host->pdata->num_slots;
> @@ -2718,7 +2642,7 @@ int dw_mci_probe(struct dw_mci *host)
>         } else {
>                 dev_dbg(host->dev, "attempted to initialize %d slots, "
>                                         "but failed on all\n", host->num_slots);
> -               goto err_workqueue;
> +               goto err_dmaunmap;
>         }
>
>         if (host->quirks & DW_MCI_QUIRK_IDMAC_DTO)
> @@ -2726,9 +2650,6 @@ int dw_mci_probe(struct dw_mci *host)
>
>         return 0;
>
> -err_workqueue:
> -       destroy_workqueue(host->card_workqueue);
> -
>  err_dmaunmap:
>         if (host->use_dma && host->dma_ops->exit)
>                 host->dma_ops->exit(host);
> @@ -2762,8 +2683,6 @@ void dw_mci_remove(struct dw_mci *host)
>         mci_writel(host, CLKENA, 0);
>         mci_writel(host, CLKSRC, 0);
>
> -       destroy_workqueue(host->card_workqueue);
> -
>         if (host->use_dma && host->dma_ops->exit)
>                 host->dma_ops->exit(host);
>
> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
> index 01b99e8..71d4995 100644
> --- a/drivers/mmc/host/dw_mmc.h
> +++ b/drivers/mmc/host/dw_mmc.h
> @@ -214,7 +214,6 @@ extern int dw_mci_resume(struct dw_mci *host);
>   *     with CONFIG_MMC_CLKGATE.
>   * @flags: Random state bits associated with the slot.
>   * @id: Number of this slot.
> - * @last_detect_state: Most recently observed card detect state.
>   */
>  struct dw_mci_slot {
>         struct mmc_host         *mmc;
> @@ -234,7 +233,6 @@ struct dw_mci_slot {
>  #define DW_MMC_CARD_PRESENT    0
>  #define DW_MMC_CARD_NEED_INIT  1
>         int                     id;
> -       int                     last_detect_state;
>  };
>
>  struct dw_mci_tuning_data {
> diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
> index 0013669..69d0814 100644
> --- a/include/linux/mmc/dw_mmc.h
> +++ b/include/linux/mmc/dw_mmc.h
> @@ -135,7 +135,6 @@ struct dw_mci {
>         struct mmc_command      stop_abort;
>         unsigned int            prev_blksz;
>         unsigned char           timing;
> -       struct workqueue_struct *card_workqueue;
>
>         /* DMA interface members*/
>         int                     use_dma;
> @@ -154,7 +153,6 @@ struct dw_mci {
>         u32                     stop_cmdr;
>         u32                     dir_status;
>         struct tasklet_struct   tasklet;
> -       struct work_struct      card_work;
>         unsigned long           pending_events;
>         unsigned long           completed_events;
>         enum dw_mci_state       state;
> --
> 2.1.0.rc2.206.gedb03e5
>
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-- 
Regards,
Alim
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