Re: [PATCH V1 4/4] scsi: ufs: Fix queue depth handling for best effort cases

[Santosh Y <santoshsy@gmail.com>]

On Tue, May 27, 2014 at 12:51 PM, Dolev Raviv <draviv@codeaurora.org> wrote:
> Some UFS devices may expose bLUQueueDepth field as zero indicating
> that the queue depth depends on the number of resources available
> for LUN at a particular instant to handle the outstanding transfer
> requests. Currently, when response for SCSI command is TASK_FULL
> the LLD decrements the queue depth but fails to increment when the
> resources are available. The scsi mid-layer handles the change in
> queue depth heuristically and offers simple interface with
> ->change_queue_depth.
>
> Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
> Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
> ---
>  drivers/scsi/ufs/ufshcd.c | 97 ++++++++++++++++++++---------------------------
>  1 file changed, 42 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index b301ed8..b103e95 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1991,27 +1991,55 @@ static int ufshcd_slave_alloc(struct scsi_device *sdev)
>
>         /* allow SCSI layer to restart the device in case of errors */
>         sdev->allow_restart = 1;
> +
>         lun_qdepth = ufshcd_read_sdev_qdepth(hba, sdev);
> -       if (lun_qdepth == 0 || lun_qdepth > hba->nutrs) {
> -               dev_info(hba->dev, "%s, lun %d queue depth is %d\n", __func__,
> -                               sdev->lun, lun_qdepth);
> +       if (lun_qdepth <= 0)
> +               /* eventually, we can figure out the real queue depth */
>                 lun_qdepth = hba->nutrs;
> -       } else if (lun_qdepth < 0) {
> -               lun_qdepth = 1;
> -       }
> +       else
> +               lun_qdepth = min_t(int, lun_qdepth, hba->nutrs);
>
> -       /*
> -        * Inform SCSI Midlayer that the LUN queue depth is same as the
> -        * controller queue depth. If a LUN queue depth is less than the
> -        * controller queue depth and if the LUN reports
> -        * SAM_STAT_TASK_SET_FULL, the LUN queue depth will be adjusted
> -        * with scsi_adjust_queue_depth.
> -        */
> +       dev_dbg(hba->dev, "%s: activate tcq with queue depth %d\n",
> +                       __func__, lun_qdepth);
>         scsi_activate_tcq(sdev, lun_qdepth);
> +
>         return 0;
>  }
>
>  /**
> + * ufshcd_change_queue_depth - change queue depth
> + * @sdev: pointer to SCSI device
> + * @depth: required depth to set
> + * @reason: reason for changing the depth
> + *
> + * Change queue depth according to the reason and make sure
> + * the max. limits are not crossed.
> + */
> +int ufshcd_change_queue_depth(struct scsi_device *sdev, int depth, int reason)
> +{
> +       struct ufs_hba *hba = shost_priv(sdev->host);
> +
> +       if (depth > hba->nutrs)
> +               depth = hba->nutrs;
> +
> +       switch (reason) {
> +       case SCSI_QDEPTH_DEFAULT:
> +       case SCSI_QDEPTH_RAMP_UP:
> +               if (!sdev->tagged_supported)
> +                       depth = 1;
> +               scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
> +               break;
> +       case SCSI_QDEPTH_QFULL:
> +               scsi_track_queue_full(sdev, depth);
> +               break;
> +       default:
> +               return -EOPNOTSUPP;
> +       }
> +
> +       return depth;
> +}
> +
> +/**
>   * ufshcd_slave_destroy - remove SCSI device configurations
>   * @sdev: pointer to SCSI device
>   */
> @@ -2064,42 +2092,6 @@ static int ufshcd_task_req_compl(struct ufs_hba *hba, u32 index, u8 *resp)
>  }
>
>  /**
> - * ufshcd_adjust_lun_qdepth - Update LUN queue depth if device responds with
> - *                           SAM_STAT_TASK_SET_FULL SCSI command status.
> - * @cmd: pointer to SCSI command
> - */
> -static void ufshcd_adjust_lun_qdepth(struct scsi_cmnd *cmd)
> -{
> -       struct ufs_hba *hba;
> -       int i;
> -       int lun_qdepth = 0;
> -
> -       hba = shost_priv(cmd->device->host);
> -
> -       /*
> -        * LUN queue depth can be obtained by counting outstanding commands
> -        * on the LUN.
> -        */
> -       for (i = 0; i < hba->nutrs; i++) {
> -               if (test_bit(i, &hba->outstanding_reqs)) {
> -
> -                       /*
> -                        * Check if the outstanding command belongs
> -                        * to the LUN which reported SAM_STAT_TASK_SET_FULL.
> -                        */
> -                       if (cmd->device->lun == hba->lrb[i].lun)
> -                               lun_qdepth++;
> -               }
> -       }
> -
> -       /*
> -        * LUN queue depth will be total outstanding commands, except the
> -        * command for which the LUN reported SAM_STAT_TASK_SET_FULL.
> -        */
> -       scsi_adjust_queue_depth(cmd->device, MSG_SIMPLE_TAG, lun_qdepth - 1);
> -}
> -
> -/**
>   * ufshcd_scsi_cmd_status - Update SCSI command result based on SCSI status
>   * @lrb: pointer to local reference block of completed command
>   * @scsi_status: SCSI command status
> @@ -2120,12 +2112,6 @@ ufshcd_scsi_cmd_status(struct ufshcd_lrb *lrbp, int scsi_status)
>                           scsi_status;
>                 break;
>         case SAM_STAT_TASK_SET_FULL:
> -               /*
> -                * If a LUN reports SAM_STAT_TASK_SET_FULL, then the LUN queue
> -                * depth needs to be adjusted to the exact number of
> -                * outstanding commands the LUN can handle at any given time.
> -                */
> -               ufshcd_adjust_lun_qdepth(lrbp->cmd);
>         case SAM_STAT_BUSY:
>         case SAM_STAT_TASK_ABORTED:
>                 ufshcd_copy_sense_data(lrbp);
> @@ -3156,6 +3142,7 @@ static struct scsi_host_template ufshcd_driver_template = {
>         .queuecommand           = ufshcd_queuecommand,
>         .slave_alloc            = ufshcd_slave_alloc,
>         .slave_destroy          = ufshcd_slave_destroy,
> +       .change_queue_depth     = ufshcd_change_queue_depth,
>         .eh_abort_handler       = ufshcd_abort,
>         .eh_device_reset_handler = ufshcd_eh_device_reset_handler,
>         .eh_host_reset_handler   = ufshcd_eh_host_reset_handler,
> --
> 1.8.5.2
>
> --

Acked-by: Santosh Y <santoshsy@gmail.com>

-- 
~Santosh