[PATCH 13/16] thunderbolt: Add polling mode for rings

From: Mika Westerberg
Date: Mon Sep 18 2017 - 11:34:45 EST

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In reply to: Mika Westerberg: "[PATCH 11/16] thunderbolt: Use spinlock in ring serialization"
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In order to support things like networking over Thunderbolt cable, there
needs to be a way to switch the ring to a mode where it can be polled
with the interrupt masked. We implement such mode so that the caller can
allocate a ring by passing pointer to a function that is then called
when an interrupt is triggered. Completed frames can be fetched using
tb_ring_poll() and the interrupt can be re-enabled when the caller is
finished with polling by using tb_ring_poll_complete().

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Reviewed-by: Michael Jamet <michael.jamet@xxxxxxxxx>
Reviewed-by: Yehezkel Bernat <yehezkel.bernat@xxxxxxxxx>
---
drivers/thunderbolt/ctl.c | 2 +-
drivers/thunderbolt/nhi.c | 126 ++++++++++++++++++++++++++++++++++++++++----
include/linux/thunderbolt.h | 23 +++++---
3 files changed, 134 insertions(+), 17 deletions(-)

diff --git a/drivers/thunderbolt/ctl.c b/drivers/thunderbolt/ctl.c
index dd10789e1dbb..d079dbba2c03 100644
--- a/drivers/thunderbolt/ctl.c
+++ b/drivers/thunderbolt/ctl.c
@@ -619,7 +619,7 @@ struct tb_ctl *tb_ctl_alloc(struct tb_nhi *nhi, event_cb cb, void *cb_data)
goto err;

ctl->rx = tb_ring_alloc_rx(nhi, 0, 10, RING_FLAG_NO_SUSPEND, 0xffff,
- 0xffff);
+ 0xffff, NULL, NULL);
if (!ctl->rx)
goto err;

diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index cf1397afa72f..5bc3f77cc1f3 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -252,7 +252,8 @@ static void ring_work(struct work_struct *work)
* Do not hold on to it.
*/
list_del_init(&frame->list);
- frame->callback(ring, frame, canceled);
+ if (frame->callback)
+ frame->callback(ring, frame, canceled);
}
}

@@ -273,11 +274,106 @@ int __tb_ring_enqueue(struct tb_ring *ring, struct ring_frame *frame)
}
EXPORT_SYMBOL_GPL(__tb_ring_enqueue);

+/**
+ * tb_ring_poll() - Poll one completed frame from the ring
+ * @ring: Ring to poll
+ *
+ * This function can be called when @start_poll callback of the @ring
+ * has been called. It will read one completed frame from the ring and
+ * return it to the caller. Returns %NULL if there is no more completed
+ * frames.
+ */
+struct ring_frame *tb_ring_poll(struct tb_ring *ring)
+{
+ struct ring_frame *frame = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&ring->lock, flags);
+ if (!ring->running)
+ goto unlock;
+ if (ring_empty(ring))
+ goto unlock;
+
+ if (ring->descriptors[ring->tail].flags & RING_DESC_COMPLETED) {
+ frame = list_first_entry(&ring->in_flight, typeof(*frame),
+ list);
+ list_del_init(&frame->list);
+
+ if (!ring->is_tx) {
+ frame->size = ring->descriptors[ring->tail].length;
+ frame->eof = ring->descriptors[ring->tail].eof;
+ frame->sof = ring->descriptors[ring->tail].sof;
+ frame->flags = ring->descriptors[ring->tail].flags;
+ }
+
+ ring->tail = (ring->tail + 1) % ring->size;
+ }
+
+unlock:
+ spin_unlock_irqrestore(&ring->lock, flags);
+ return frame;
+}
+EXPORT_SYMBOL_GPL(tb_ring_poll);
+
+static void __ring_interrupt_mask(struct tb_ring *ring, bool mask)
+{
+ int idx = ring_interrupt_index(ring);
+ int reg = REG_RING_INTERRUPT_BASE + idx / 32 * 4;
+ int bit = idx % 32;
+ u32 val;
+
+ val = ioread32(ring->nhi->iobase + reg);
+ if (mask)
+ val &= ~BIT(bit);
+ else
+ val |= BIT(bit);
+ iowrite32(val, ring->nhi->iobase + reg);
+}
+
+/* Both @nhi->lock and @ring->lock should be held */
+static void __ring_interrupt(struct tb_ring *ring)
+{
+ if (!ring->running)
+ return;
+
+ if (ring->start_poll) {
+ __ring_interrupt_mask(ring, false);
+ ring->start_poll(ring->poll_data);
+ } else {
+ schedule_work(&ring->work);
+ }
+}
+
+/**
+ * tb_ring_poll_complete() - Re-start interrupt for the ring
+ * @ring: Ring to re-start the interrupt
+ *
+ * This will re-start (unmask) the ring interrupt once the user is done
+ * with polling.
+ */
+void tb_ring_poll_complete(struct tb_ring *ring)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&ring->nhi->lock, flags);
+ spin_lock(&ring->lock);
+ if (ring->start_poll)
+ __ring_interrupt_mask(ring, false);
+ spin_unlock(&ring->lock);
+ spin_unlock_irqrestore(&ring->nhi->lock, flags);
+}
+EXPORT_SYMBOL_GPL(tb_ring_poll_complete);
+
static irqreturn_t ring_msix(int irq, void *data)
{
struct tb_ring *ring = data;

- schedule_work(&ring->work);
+ spin_lock(&ring->nhi->lock);
+ spin_lock(&ring->lock);
+ __ring_interrupt(ring);
+ spin_unlock(&ring->lock);
+ spin_unlock(&ring->nhi->lock);
+
return IRQ_HANDLED;
}

@@ -317,7 +413,9 @@ static void ring_release_msix(struct tb_ring *ring)

static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
bool transmit, unsigned int flags,
- u16 sof_mask, u16 eof_mask)
+ u16 sof_mask, u16 eof_mask,
+ void (*start_poll)(void *),
+ void *poll_data)
{
struct tb_ring *ring = NULL;
dev_info(&nhi->pdev->dev, "allocating %s ring %d of size %d\n",
@@ -346,6 +444,8 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
ring->head = 0;
ring->tail = 0;
ring->running = false;
+ ring->start_poll = start_poll;
+ ring->poll_data = poll_data;

ring->descriptors = dma_alloc_coherent(&ring->nhi->pdev->dev,
size * sizeof(*ring->descriptors),
@@ -399,7 +499,7 @@ static struct tb_ring *tb_ring_alloc(struct tb_nhi *nhi, u32 hop, int size,
struct tb_ring *tb_ring_alloc_tx(struct tb_nhi *nhi, int hop, int size,
unsigned int flags)
{
- return tb_ring_alloc(nhi, hop, size, true, flags, 0, 0);
+ return tb_ring_alloc(nhi, hop, size, true, flags, 0, 0, NULL, NULL);
}
EXPORT_SYMBOL_GPL(tb_ring_alloc_tx);

@@ -411,11 +511,17 @@ EXPORT_SYMBOL_GPL(tb_ring_alloc_tx);
* @flags: Flags for the ring
* @sof_mask: Mask of PDF values that start a frame
* @eof_mask: Mask of PDF values that end a frame
+ * @start_poll: If not %NULL the ring will call this function when an
+ * interrupt is triggered and masked, instead of callback
+ * in each Rx frame.
+ * @poll_data: Optional data passed to @start_poll
*/
struct tb_ring *tb_ring_alloc_rx(struct tb_nhi *nhi, int hop, int size,
- unsigned int flags, u16 sof_mask, u16 eof_mask)
+ unsigned int flags, u16 sof_mask, u16 eof_mask,
+ void (*start_poll)(void *), void *poll_data)
{
- return tb_ring_alloc(nhi, hop, size, false, flags, sof_mask, eof_mask);
+ return tb_ring_alloc(nhi, hop, size, false, flags, sof_mask, eof_mask,
+ start_poll, poll_data);
}
EXPORT_SYMBOL_GPL(tb_ring_alloc_rx);

@@ -556,6 +662,7 @@ void tb_ring_free(struct tb_ring *ring)
dev_WARN(&ring->nhi->pdev->dev, "%s %d still running\n",
RING_TYPE(ring), ring->hop);
}
+ spin_unlock_irq(&ring->nhi->lock);

ring_release_msix(ring);

@@ -572,7 +679,6 @@ void tb_ring_free(struct tb_ring *ring)
RING_TYPE(ring),
ring->hop);

- spin_unlock_irq(&ring->nhi->lock);
/**
* ring->work can no longer be scheduled (it is scheduled only
* by nhi_interrupt_work, ring_stop and ring_msix). Wait for it
@@ -682,8 +788,10 @@ static void nhi_interrupt_work(struct work_struct *work)
hop);
continue;
}
- /* we do not check ring->running, this is done in ring->work */
- schedule_work(&ring->work);
+
+ spin_lock(&ring->lock);
+ __ring_interrupt(ring);
+ spin_unlock(&ring->lock);
}
spin_unlock_irq(&nhi->lock);
}
diff --git a/include/linux/thunderbolt.h b/include/linux/thunderbolt.h
index 62adb97d77f1..9a63210d5084 100644
--- a/include/linux/thunderbolt.h
+++ b/include/linux/thunderbolt.h
@@ -446,6 +446,9 @@ struct tb_nhi {
* @flags: Ring specific flags
* @sof_mask: Bit mask used to detect start of frame PDF
* @eof_mask: Bit mask used to detect end of frame PDF
+ * @start_poll: Called when ring interrupt is triggered to start
+ * polling. Passing %NULL keeps the ring in interrupt mode.
+ * @poll_data: Data passed to @start_poll
*/
struct tb_ring {
spinlock_t lock;
@@ -466,6 +469,8 @@ struct tb_ring {
unsigned int flags;
u16 sof_mask;
u16 eof_mask;
+ void (*start_poll)(void *data);
+ void *poll_data;
};

/* Leave ring interrupt enabled on suspend */
@@ -499,7 +504,7 @@ enum ring_desc_flags {
/**
* struct ring_frame - For use with ring_rx/ring_tx
* @buffer_phy: DMA mapped address of the frame
- * @callback: Callback called when the frame is finished
+ * @callback: Callback called when the frame is finished (optional)
* @list: Frame is linked to a queue using this
* @size: Size of the frame in bytes (%0 means %4096)
* @flags: Flags for the frame (see &enum ring_desc_flags)
@@ -522,8 +527,8 @@ struct ring_frame {
struct tb_ring *tb_ring_alloc_tx(struct tb_nhi *nhi, int hop, int size,
unsigned int flags);
struct tb_ring *tb_ring_alloc_rx(struct tb_nhi *nhi, int hop, int size,
- unsigned int flags, u16 sof_mask,
- u16 eof_mask);
+ unsigned int flags, u16 sof_mask, u16 eof_mask,
+ void (*start_poll)(void *), void *poll_data);
void tb_ring_start(struct tb_ring *ring);
void tb_ring_stop(struct tb_ring *ring);
void tb_ring_free(struct tb_ring *ring);
@@ -535,8 +540,8 @@ int __tb_ring_enqueue(struct tb_ring *ring, struct ring_frame *frame);
* @ring: Ring to enqueue the frame
* @frame: Frame to enqueue
*
- * @frame->buffer, @frame->buffer_phy and @frame->callback have to be set. The
- * buffer must contain at least %TB_FRAME_SIZE bytes.
+ * @frame->buffer, @frame->buffer_phy have to be set. The buffer must
+ * contain at least %TB_FRAME_SIZE bytes.
*
* @frame->callback will be invoked with @frame->size, @frame->flags,
* @frame->eof, @frame->sof set once the frame has been received.
@@ -557,8 +562,8 @@ static inline int tb_ring_rx(struct tb_ring *ring, struct ring_frame *frame)
* @ring: Ring the enqueue the frame
* @frame: Frame to enqueue
*
- * @frame->buffer, @frame->buffer_phy, @frame->callback, @frame->size,
- * @frame->eof and @frame->sof have to be set.
+ * @frame->buffer, @frame->buffer_phy, @frame->size, @frame->eof and
+ * @frame->sof have to be set.
*
* @frame->callback will be invoked with once the frame has been transmitted.
*
@@ -573,4 +578,8 @@ static inline int tb_ring_tx(struct tb_ring *ring, struct ring_frame *frame)
return __tb_ring_enqueue(ring, frame);
}

+/* Used only when the ring is in polling mode */
+struct ring_frame *tb_ring_poll(struct tb_ring *ring);
+void tb_ring_poll_complete(struct tb_ring *ring);
+
#endif /* THUNDERBOLT_H_ */
--
2.13.5

Next message: Mika Westerberg: "[PATCH 05/16] thunderbolt: Move tb_switch_phy_port_from_link() to thunderbolt.h"
Previous message: Pablo Neira Ayuso: "Re: [PATCH] netfilter: nat: Do not use ARRAY_SIZE() on spinlocks to fix zero div"
In reply to: Mika Westerberg: "[PATCH 11/16] thunderbolt: Use spinlock in ring serialization"
Next in thread: Mika Westerberg: "[PATCH 05/16] thunderbolt: Move tb_switch_phy_port_from_link() to thunderbolt.h"
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