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    SubjectRe: [PATCH v3 39/77] ncr5380: Standardize interrupt handling
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    On 12/22/2015 02:18 AM, Finn Thain wrote:
    > Because interrupt handling is crucial to the core driver(s), all wrapper
    > drivers need to agree on this code. This patch removes discrepancies.
    >
    > NCR5380_intr() in NCR5380.c has the following pointless loop that differs
    > from the code in atari_NCR5380.c.
    >
    > done = 1;
    > do {
    > /* ... */
    > } while (!done);
    >
    > The 'done' flag gets cleared when a reconnected command is to be processed
    > from the work queue. But in NCR5380.c, the flag is also used to cause the
    > interrupt conditions to be re-examined. Perhaps this was because
    > NCR5380_reselect() was expected to cause another interrupt, or perhaps
    > the remaining present interrupt conditions need to be handled after the
    > NCR5380_reselect() call?
    >
    > Actually, both possibilities are bogus, as is the loop itself. It seems
    > have been overlooked in the hit-and-miss removal of scsi host instance
    > list iteration many years ago; see history/history.git commit 491447e1fcff
    > ("[PATCH] next NCR5380 updates") and commit 69e1a9482e57 ("[PATCH] fix up
    > NCR5380 private data"). See also my earlier patch, "Always retry
    > arbitration and selection".
    >
    > The datasheet says, "IRQ can be reset simply by reading the Reset
    > Parity/Interrupt Register". So don't treat the chip IRQ like a
    > level-triggered interrupt. Of the conditions that set the IRQ flag,
    > some are level-triggered and some are edge-triggered, which means IRQ
    > itself must be edge-triggered.
    >
    > Some interrupt conditions are latched and some are not. Before clearing
    > the chip IRQ flag, clear all state that may cause it to be raised. That
    > means clearing the DMA Mode and Busy Monitor bits in the Mode Register
    > and clearing the host ID in the Select Enable register.
    >
    > Also clean up some printk's and some comments. Keep atari_NCR5380.c and
    > NCR5380.c in agreement.
    >
    > Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
    >
    > ---
    > drivers/scsi/NCR5380.c | 187 +++++++++++++++++++++++--------------------
    > drivers/scsi/atari_NCR5380.c | 156 +++++++++++++++++------------------
    > drivers/scsi/dtc.c | 8 -
    > drivers/scsi/g_NCR5380.c | 2
    > 4 files changed, 180 insertions(+), 173 deletions(-)
    >
    Reviewed-by: Hannes Reinecke <hare@suse.com>

    Cheers,

    Hannes
    --
    Dr. Hannes Reinecke zSeries & Storage
    hare@suse.de +49 911 74053 688
    SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
    GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)


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