Re: [PATCH 1/3] libsas: modify SATA error handler

[Dan Williams]

Hi, some notes below:

On Thu, Apr 24, 2014 at 6:27 AM, Xiangliang Yu <yxlraid@xxxxxxxxx> wrote:
> Add support for SATA port softreset and port multiplier error
> handling.

Some more detailed notes about the approach and any caveats would be
appreciated.

>
> Signed-off-by: Xiangliang Yu <yxlraid@xxxxxxxxx>
> ---
>  drivers/scsi/libsas/sas_ata.c |  226 ++++++++++++++++++++++++++++++++++++++++-
>  include/scsi/libsas.h         |    6 +
>  2 files changed, 231 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
> index 766098a..29a19fd 100644
> --- a/drivers/scsi/libsas/sas_ata.c
> +++ b/drivers/scsi/libsas/sas_ata.c
> @@ -442,6 +442,226 @@ static int sas_ata_hard_reset(struct ata_link *link, unsigned int *class,
>         return ret;
>  }
>
> +static void sas_ata_freeze(struct ata_port *ap)
> +{
> +       struct domain_device *dev = ap->private_data;
> +       struct sas_ha_struct *sas_ha = dev->port->ha;
> +       struct Scsi_Host *host = sas_ha->core.shost;
> +       struct sas_internal *i = to_sas_internal(host->transportt);
> +
> +       if (i->dft->lldd_dev_freeze)
> +               i->dft->lldd_dev_freeze(dev);
> +}
> +
> +static void sas_ata_thaw(struct ata_port *ap)
> +{
> +       struct domain_device *dev = ap->private_data;
> +       struct sas_ha_struct *sas_ha = dev->port->ha;
> +       struct Scsi_Host *host = sas_ha->core.shost;
> +       struct sas_internal *i = to_sas_internal(host->transportt);
> +
> +       if (i->dft->lldd_dev_thaw)
> +               i->dft->lldd_dev_thaw(dev);
> +}
> +
> +static int sas_ata_wait_task_done(struct sas_task *task, unsigned long timeout,
> +               int (*check_done)(struct sas_task *task))
> +{

Why do we need a custom check_done() routine?  Since we have a
sas_task we can use the normal completion infrastructure.  See
smp_execute_task().

> +       struct ata_port *ap = task->uldd_task;
> +       unsigned long deadline;
> +       int done;
> +
> +       if (!check_done) {
> +               SAS_DPRINTK("check function is null.\n");
> +               return -1;
> +       }
> +
> +       deadline = ata_deadline(jiffies, timeout);
> +       done = check_done(task);
> +
> +       while (done && time_before(jiffies, deadline)) {
> +               ata_msleep(ap, 1);
> +
> +               done = check_done(task);

This can simply be:

completion_done(&task->slow_task->completion)

> +       }
> +
> +       return done;
> +}
> +
> +static int sas_ata_exec_polled_cmd(struct ata_port *ap, struct ata_taskfile *tf,
> +               int pmp, unsigned long timeout)
> +{
> +       struct domain_device *dev = ap->private_data;
> +       struct sas_ha_struct *sas_ha = dev->port->ha;
> +       struct Scsi_Host *host = sas_ha->core.shost;
> +       struct sas_internal *i = to_sas_internal(host->transportt);
> +       struct sas_task *task = NULL;
> +       int ret = -1;
> +
> +       if (!i->dft->lldd_execute_task) {
> +               SAS_DPRINTK("execute function is null.\n");
> +               return ret;
> +       }
> +
> +       task = sas_alloc_task(GFP_ATOMIC);

I think this can be downgraded to GFP_NOIO.  We're in a sleepable context.

> +       if (!task) {
> +               SAS_DPRINTK("failed to alloc sas task.\n");
> +               goto fail;
> +       }
> +
> +       task->dev = dev;
> +       task->task_proto = SAS_PROTOCOL_SATA;
> +       task->uldd_task = ap;
> +
> +       ata_tf_to_fis(tf, pmp, 0, (u8 *)&task->ata_task.fis);
> +       task->ata_task.retry_count = 1;
> +       task->task_state_flags = SAS_TASK_STATE_PENDING;
> +       task->task_state_flags |= SAS_TASK_NEED_DEV_RESET;
> +
> +       ret = i->dft->lldd_execute_task(task, 1, GFP_ATOMIC);

Same here.

> +       if (ret) {
> +               SAS_DPRINTK("failed to send internal task.\n");
> +               goto fail;
> +       }
> +
> +       if (timeout) {
> +               ret = sas_ata_wait_task_done(task, timeout,
> +                               i->dft->lldd_wait_task_done);
> +               if (ret) {
> +                       SAS_DPRINTK("get wrong status.\n");
> +                       goto fail;
> +               }
> +       }
> +       list_del_init(&task->list);
> +       sas_free_task(task);
> +
> +       return 0;
> +fail:
> +       if (task) {
> +               list_del_init(&task->list);
> +               sas_free_task(task);
> +       }
> +
> +       return ret;
> +}
> +
> +static int sas_ata_soft_reset(struct ata_link *link, unsigned int *class,
> +                             unsigned long deadline)
> +{
> +       struct ata_taskfile tf;
> +       struct ata_port *ap = link->ap;
> +       struct domain_device *dev = ap->private_data;
> +       struct sas_ha_struct *sas_ha = dev->port->ha;
> +       struct Scsi_Host *host = sas_ha->core.shost;
> +       struct sas_internal *i = to_sas_internal(host->transportt);
> +       struct sas_phy *phy;
> +       unsigned long now, msecs;
> +       unsigned int pmp;
> +       int ret = -1;
> +       int (*check_ready)(struct ata_link *link);
> +
> +       phy = sas_get_local_phy(dev);
> +       if (scsi_is_sas_phy_local(phy))
> +               check_ready = local_ata_check_ready;
> +       else
> +               check_ready = smp_ata_check_ready;
> +       sas_put_local_phy(phy);

Does this attempt to support expander attached port multiplier's?
Last I checked expanders do not support this so we should just fail
this for non-local phys.

> +
> +       pmp = sata_srst_pmp(link);
> +
> +       msecs = 0;
> +       now = jiffies;
> +       if (time_after(deadline, now))
> +               msecs = jiffies_to_msecs(deadline - now);
> +
> +       memset(&tf, 0, sizeof(struct ata_taskfile));
> +       tf.ctl = ATA_SRST;
> +       tf.device = ATA_DEVICE_OBS;
> +
> +       if (sas_ata_exec_polled_cmd(ap, &tf, pmp, msecs)) {
> +               ret = -EIO;
> +               goto fail;
> +       }
> +
> +       tf.ctl &= ~ATA_SRST;
> +       sas_ata_exec_polled_cmd(ap, &tf, pmp, msecs);

What about lldd's that do not know how to handle ATA_SRST?  I think we
need preparation patches to make SRST support opt-in, or teach all
lldds how to handle these SRST sas_tasks.

> +
> +       ret = ata_wait_after_reset(link, deadline, check_ready);
> +       if (ret) {
> +               SAS_DPRINTK("device is not ready.\n");
> +               ret = -EIO;
> +               goto fail;
> +       } else {
> +               if (i->dft->lldd_dev_classify)
> +                       *class = i->dft->lldd_dev_classify(dev);
> +       }
> +
> +       return 0;
> +
> +fail:
> +       SAS_DPRINTK("failed to reset.\n");
> +       return ret;
> +}
> +
> +/* According sata 3.0 spec 13.15.4.2, enable the device port */
> +static int sas_ata_pmp_hard_reset(struct ata_link *link, unsigned int *class,
> +                             unsigned long deadline)
> +{
> +       struct ata_port *ap = link->ap;
> +       struct domain_device *dev = ap->private_data;
> +       struct sas_ha_struct *sas_ha = dev->port->ha;
> +       struct Scsi_Host *host = sas_ha->core.shost;
> +       struct sas_internal *i = to_sas_internal(host->transportt);
> +       int ret = -1;
> +       u32 scontrol = 0;
> +
> +       set_bit(SAS_DEV_RESET, &dev->state);
> +
> +       ret = sata_scr_read(link, SCR_CONTROL, &scontrol);

I think a comment is needed clarifying that these reads generate
sas_tasks to a pmp and are not trying to read/write local SCR
registers that do not exist on a SAS hba.

> +       if (ret)
> +               goto error;
> +
> +       /* enable device port */
> +       scontrol = 0x1;
> +       ret = sata_scr_write(link, SCR_CONTROL, scontrol);
> +       if (ret)
> +               goto error;
> +
> +       ata_msleep(ap, 1);
> +
> +       scontrol = 0x0;
> +       ret = sata_scr_write(link, SCR_CONTROL, scontrol);
> +       if (ret)
> +               goto error;
> +
> +       ata_msleep(ap, 10);
> +
> +       /* check device link status */
> +       if (ata_link_offline(link)) {
> +               SAS_DPRINTK("link is offline.\n");
> +               goto error;
> +       }
> +
> +       /* clear X bit */
> +       scontrol = 0xFFFFFFFF;
> +       ret = sata_scr_write(link, SCR_ERROR, scontrol);
> +       if (ret)
> +               goto error;
> +
> +       /* may be need to wait for device sig */
> +       ata_msleep(ap, 3);
> +
> +       /* check device class */
> +       if (i->dft->lldd_dev_classify)
> +               *class = i->dft->lldd_dev_classify(dev);
> +
> +       return 0;
> +
> +error:
> +       SAS_DPRINTK("failed to hard reset.\n");
> +       return ret;
> +}
> +
>  /*
>   * notify the lldd to forget the sas_task for this internal ata command
>   * that bypasses scsi-eh
> @@ -551,8 +771,12 @@ void sas_ata_end_eh(struct ata_port *ap)
>  static struct ata_port_operations sas_sata_ops = {
>         .prereset               = ata_std_prereset,
>         .hardreset              = sas_ata_hard_reset,
> +       .softreset              = sas_ata_soft_reset,
> +       .pmp_hardreset          = sas_ata_pmp_hard_reset,
> +       .freeze                 = sas_ata_freeze,
> +       .thaw                   = sas_ata_thaw,
>         .postreset              = ata_std_postreset,
> -       .error_handler          = ata_std_error_handler,
> +       .error_handler          = sata_pmp_error_handler,
>         .post_internal_cmd      = sas_ata_post_internal,
>         .qc_defer               = ata_std_qc_defer,
>         .qc_prep                = ata_noop_qc_prep,
> diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
> index ef7872c..a26466a 100644
> --- a/include/scsi/libsas.h
> +++ b/include/scsi/libsas.h
> @@ -689,6 +689,12 @@ struct sas_domain_function_template {
>         /* GPIO support */
>         int (*lldd_write_gpio)(struct sas_ha_struct *, u8 reg_type,
>                                u8 reg_index, u8 reg_count, u8 *write_data);
> +
> +       /* ATA EH functions */
> +       void (*lldd_dev_freeze)(struct domain_device *);

Why do we need to pass this all the way through to the lldd?  Can we
get away with emulating this in sas_ata.c.

> +       void (*lldd_dev_thaw)(struct domain_device *);

Same note as lldd_dev_freeze

> +       int (*lldd_wait_task_done)(struct sas_task *);

Should not be needed.

> +       int (*lldd_dev_classify)(struct domain_device *);

I think this belongs in a different patch set.  If we solve device
re-classification for soft reset we need to do the same for the
sas_ata_hard_reset path.
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