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    SubjectRe: [PATCH 11/12] libata: use IRQ expecting
    Hello, Jeff.

    So, something like the following. This should be applied on top of
    the two previous libata patches. The amount of code in the hot path
    is very small. Compared to the cpu actually taking an interrupt and
    accessing hardware, it should be negligible, and this will give us
    working and acceptably performing systems in the presence of most
    types of IRQ problems.

    Thanks.

    Subject: [PATCH] libata: use IRQ expecting

    Legacy ATA is very susceptible to IRQ delivery problems in both
    directions - lost and spurious interrupts. In traditional PATA, the
    IRQ line is ultimately out of the controller and driver's control.

    Even relatively new SATA controllers share this problem as many still
    emulate the traditional IDE interface which doesn't have reliable way
    to indicate interrupt pending state and there also is an issue
    regarding the interpretation of nIEN on both sides of the cable.

    Controllers with native interface have fewer problems compared to the
    ones which use SFF but they still are affected by IRQ misrouting or
    broken MSI implementations.

    IRQ delivery problems on ATA are particularly nasty because it
    commonly hosts installation and/or booting.

    Most of these problems can be worked around by using the new IRQ
    expecting mechanism without adding any noticeable overhead. In ATA,
    almost all operations are initiated by the host and the controller
    signals progress or completion using IRQ. IRQ expecting can easily be
    added in libata core and applied to all libata drivers.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    drivers/ata/libata-core.c | 55 ++++++++++++++++++++++++++++++----------------
    drivers/ata/libata-eh.c | 4 ++-
    drivers/ata/libata-sff.c | 37 +++++++++++++++---------------
    include/linux/libata.h | 2 +
    4 files changed, 60 insertions(+), 38 deletions(-)

    Index: work/drivers/ata/libata-core.c
    ===================================================================
    --- work.orig/drivers/ata/libata-core.c
    +++ work/drivers/ata/libata-core.c
    @@ -4958,22 +4958,7 @@ static void ata_verify_xfer(struct ata_q
    dev->flags &= ~ATA_DFLAG_DUBIOUS_XFER;
    }

    -/**
    - * ata_qc_complete - Complete an active ATA command
    - * @qc: Command to complete
    - *
    - * Indicate to the mid and upper layers that an ATA command has
    - * completed, with either an ok or not-ok status.
    - *
    - * Refrain from calling this function multiple times when
    - * successfully completing multiple NCQ commands.
    - * ata_qc_complete_multiple() should be used instead, which will
    - * properly update IRQ expect state.
    - *
    - * LOCKING:
    - * spin_lock_irqsave(host lock)
    - */
    -void ata_qc_complete(struct ata_queued_cmd *qc)
    +static void ata_qc_complete_raw(struct ata_queued_cmd *qc)
    {
    struct ata_port *ap = qc->ap;

    @@ -5052,6 +5037,27 @@ void ata_qc_complete(struct ata_queued_c
    }

    /**
    + * ata_qc_complete - Complete an active ATA command
    + * @qc: Command to complete
    + *
    + * Indicate to the mid and upper layers that an ATA command has
    + * completed, with either an ok or not-ok status.
    + *
    + * Refrain from calling this function multiple times when
    + * successfully completing multiple NCQ commands.
    + * ata_qc_complete_multiple() should be used instead, which will
    + * properly update IRQ expect state.
    + *
    + * LOCKING:
    + * spin_lock_irqsave(host lock)
    + */
    +void ata_qc_complete(struct ata_queued_cmd *qc)
    +{
    + unexpect_irq(qc->ap->irq_expect, false);
    + ata_qc_complete_raw(qc);
    +}
    +
    +/**
    * ata_qc_complete_multiple - Complete multiple qcs successfully
    * @ap: port in question
    * @qc_active: new qc_active mask
    @@ -5076,6 +5082,8 @@ int ata_qc_complete_multiple(struct ata_
    int nr_done = 0;
    u32 done_mask;

    + unexpect_irq(ap->irq_expect, false);
    +
    done_mask = ap->qc_active ^ qc_active;

    if (unlikely(done_mask & qc_active)) {
    @@ -5090,12 +5098,15 @@ int ata_qc_complete_multiple(struct ata_

    qc = ata_qc_from_tag(ap, tag);
    if (qc) {
    - ata_qc_complete(qc);
    + ata_qc_complete_raw(qc);
    nr_done++;
    }
    done_mask &= ~(1 << tag);
    }

    + if (ap->qc_active)
    + expect_irq(ap->irq_expect);
    +
    return nr_done;
    }

    @@ -5162,6 +5173,7 @@ void ata_qc_issue(struct ata_queued_cmd
    qc->err_mask |= ap->ops->qc_issue(qc);
    if (unlikely(qc->err_mask))
    goto err;
    + expect_irq(ap->irq_expect);
    return;

    sg_err:
    @@ -6194,8 +6206,13 @@ int ata_host_activate(struct ata_host *h
    if (rc)
    return rc;

    - for (i = 0; i < host->n_ports; i++)
    - ata_port_desc(host->ports[i], "irq %d", irq);
    + for (i = 0; i < host->n_ports; i++) {
    + struct ata_port *ap = host->ports[i];
    +
    + if (!ata_port_is_dummy(ap))
    + ap->irq_expect = init_irq_expect(irq, host);
    + ata_port_desc(ap, "irq %d%s", irq, ap->irq_expect ? "+" : "");
    + }

    rc = ata_host_register(host, sht);
    /* if failed, just free the IRQ and leave ports alone */
    Index: work/drivers/ata/libata-eh.c
    ===================================================================
    --- work.orig/drivers/ata/libata-eh.c
    +++ work/drivers/ata/libata-eh.c
    @@ -619,8 +619,10 @@ void ata_scsi_error(struct Scsi_Host *ho
    * handler doesn't diddle with those qcs. This must
    * be done atomically w.r.t. setting QCFLAG_FAILED.
    */
    - if (nr_timedout)
    + if (nr_timedout) {
    + unexpect_irq(ap->irq_expect, true);
    __ata_port_freeze(ap);
    + }

    spin_unlock_irqrestore(ap->lock, flags);

    Index: work/include/linux/libata.h
    ===================================================================
    --- work.orig/include/linux/libata.h
    +++ work/include/linux/libata.h
    @@ -751,6 +751,8 @@ struct ata_port {
    struct ata_host *host;
    struct device *dev;

    + struct irq_expect *irq_expect; /* for irq expecting */
    +
    struct delayed_work hotplug_task;
    struct work_struct scsi_rescan_task;

    Index: work/drivers/ata/libata-sff.c
    ===================================================================
    --- work.orig/drivers/ata/libata-sff.c
    +++ work/drivers/ata/libata-sff.c
    @@ -2388,7 +2388,8 @@ int ata_pci_sff_activate_host(struct ata
    struct device *dev = host->dev;
    struct pci_dev *pdev = to_pci_dev(dev);
    const char *drv_name = dev_driver_string(host->dev);
    - int legacy_mode = 0, rc;
    + struct ata_port *ap[2] = { host->ports[0], host->ports[1] };
    + int legacy_mode = 0, i, rc;

    rc = ata_host_start(host);
    if (rc)
    @@ -2422,29 +2423,29 @@ int ata_pci_sff_activate_host(struct ata
    if (rc)
    goto out;

    - ata_port_desc(host->ports[0], "irq %d", pdev->irq);
    - ata_port_desc(host->ports[1], "irq %d", pdev->irq);
    + for (i = 0; i < 2; i++) {
    + if (!ata_port_is_dummy(ap[i]))
    + ap[i]->irq_expect =
    + init_irq_expect(pdev->irq, host);
    + ata_port_desc(ap[i], "irq %d%s",
    + pdev->irq, ap[i]->irq_expect ? "+" : "");
    + }
    } else if (legacy_mode) {
    - if (!ata_port_is_dummy(host->ports[0])) {
    - rc = devm_request_irq(dev, ATA_PRIMARY_IRQ(pdev),
    - irq_handler, IRQF_SHARED,
    - drv_name, host);
    - if (rc)
    - goto out;
    + unsigned int irqs[2] = { ATA_PRIMARY_IRQ(pdev),
    + ATA_SECONDARY_IRQ(pdev) };

    - ata_port_desc(host->ports[0], "irq %d",
    - ATA_PRIMARY_IRQ(pdev));
    - }
    + for (i = 0; i < 2; i++) {
    + if (ata_port_is_dummy(ap[i]))
    + continue;

    - if (!ata_port_is_dummy(host->ports[1])) {
    - rc = devm_request_irq(dev, ATA_SECONDARY_IRQ(pdev),
    - irq_handler, IRQF_SHARED,
    - drv_name, host);
    + rc = devm_request_irq(dev, irqs[i], irq_handler,
    + IRQF_SHARED, drv_name, host);
    if (rc)
    goto out;

    - ata_port_desc(host->ports[1], "irq %d",
    - ATA_SECONDARY_IRQ(pdev));
    + ap[i]->irq_expect = init_irq_expect(irqs[i], host);
    + ata_port_desc(ap[i], "irq %d%s",
    + irqs[i], ap[i]->irq_expect ? "+" : "");
    }
    }



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