[ 022/180] ioat2: kill pending flag

From: Willy Tarreau
Date: Mon Oct 01 2012 - 20:10:14 EST


2.6.32-longterm review patch. If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit 281befa5592b0c5f9a3856b5666c62ac66d3d9ee upstream.

The pending == 2 case no longer exists in the driver so, we can use
ioat2_ring_pending() outside the lock to determine if there might be any
descriptors in the ring that the hardware has not seen.

Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Backported-by: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
drivers/dma/ioat/dma_v2.c | 34 ++++++++++++----------------------
drivers/dma/ioat/dma_v2.h | 2 --
2 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 5cc37af..d1be371 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -51,48 +51,40 @@ MODULE_PARM_DESC(ioat_ring_max_alloc_order,

void __ioat2_issue_pending(struct ioat2_dma_chan *ioat)
{
- void * __iomem reg_base = ioat->base.reg_base;
+ struct ioat_chan_common *chan = &ioat->base;

- ioat->pending = 0;
ioat->dmacount += ioat2_ring_pending(ioat);
ioat->issued = ioat->head;
/* make descriptor updates globally visible before notifying channel */
wmb();
- writew(ioat->dmacount, reg_base + IOAT_CHAN_DMACOUNT_OFFSET);
- dev_dbg(to_dev(&ioat->base),
+ writew(ioat->dmacount, chan->reg_base + IOAT_CHAN_DMACOUNT_OFFSET);
+ dev_dbg(to_dev(chan),
"%s: head: %#x tail: %#x issued: %#x count: %#x\n",
__func__, ioat->head, ioat->tail, ioat->issued, ioat->dmacount);
}

-void ioat2_issue_pending(struct dma_chan *chan)
+void ioat2_issue_pending(struct dma_chan *c)
{
- struct ioat2_dma_chan *ioat = to_ioat2_chan(chan);
+ struct ioat2_dma_chan *ioat = to_ioat2_chan(c);

- spin_lock_bh(&ioat->ring_lock);
- if (ioat->pending == 1)
+ if (ioat2_ring_pending(ioat)) {
+ spin_lock_bh(&ioat->ring_lock);
__ioat2_issue_pending(ioat);
- spin_unlock_bh(&ioat->ring_lock);
+ spin_unlock_bh(&ioat->ring_lock);
+ }
}

/**
* ioat2_update_pending - log pending descriptors
* @ioat: ioat2+ channel
*
- * set pending to '1' unless pending is already set to '2', pending == 2
- * indicates that submission is temporarily blocked due to an in-flight
- * reset. If we are already above the ioat_pending_level threshold then
- * just issue pending.
- *
- * called with ring_lock held
+ * Check if the number of unsubmitted descriptors has exceeded the
+ * watermark. Called with ring_lock held
*/
static void ioat2_update_pending(struct ioat2_dma_chan *ioat)
{
- if (unlikely(ioat->pending == 2))
- return;
- else if (ioat2_ring_pending(ioat) > ioat_pending_level)
+ if (ioat2_ring_pending(ioat) > ioat_pending_level)
__ioat2_issue_pending(ioat);
- else
- ioat->pending = 1;
}

static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
@@ -546,7 +538,6 @@ int ioat2_alloc_chan_resources(struct dma_chan *c)
ioat->head = 0;
ioat->issued = 0;
ioat->tail = 0;
- ioat->pending = 0;
ioat->alloc_order = order;
spin_unlock_bh(&ioat->ring_lock);

@@ -815,7 +806,6 @@ void ioat2_free_chan_resources(struct dma_chan *c)

chan->last_completion = 0;
chan->completion_dma = 0;
- ioat->pending = 0;
ioat->dmacount = 0;
}

diff --git a/drivers/dma/ioat/dma_v2.h b/drivers/dma/ioat/dma_v2.h
index 3afad8d..d211335 100644
--- a/drivers/dma/ioat/dma_v2.h
+++ b/drivers/dma/ioat/dma_v2.h
@@ -47,7 +47,6 @@ extern int ioat_ring_alloc_order;
* @head: allocated index
* @issued: hardware notification point
* @tail: cleanup index
- * @pending: lock free indicator for issued != head
* @dmacount: identical to 'head' except for occasionally resetting to zero
* @alloc_order: log2 of the number of allocated descriptors
* @ring: software ring buffer implementation of hardware ring
@@ -61,7 +60,6 @@ struct ioat2_dma_chan {
u16 tail;
u16 dmacount;
u16 alloc_order;
- int pending;
struct ioat_ring_ent **ring;
spinlock_t ring_lock;
};
--
1.7.2.1.45.g54fbc



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/