[PATCH net-next 08/13] net: ipa: only enable GSI event control IRQs when needed

[Alex Elder <elder@linaro.org>]

A GSI event ring causes an event control interrupt to fire whenever
its state changes (between NOT_ALLOCATED and ALLOCATED).  No event
ring should ever change state except when we request it to.

Currently, we permit *all* events rings to generate event control
interrupts--even those that are never used.  And we enable event
control interrupts essentially at all times, from setup to teardown.

Instead, only enable the event control interrupt type for the
duration of an event ring command, and when doing so, only allow
the event ring being operated upon to cause the interrupt to fire.
Disallow all event rings from issuing the event control interrupt
in gsi_irq_setup().

Because an event ring's interrupt is only enabled when needed,
there is no longer any need to zero the event channel mask in
gsi_irq_disable().

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/gsi.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 4fc72dfe1e9b0..2c01a04e07b70 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -256,6 +256,7 @@ static void gsi_irq_setup(struct gsi *gsi)
 	gsi_irq_type_update(gsi);
 
 	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
 }
 
 /* Turn off all GSI interrupts when we're all done */
@@ -288,10 +289,6 @@ static void gsi_irq_enable(struct gsi *gsi)
 {
 	u32 val;
 
-	val = GENMASK(gsi->evt_ring_count - 1, 0);
-	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
-	gsi->type_enabled_bitmap |= BIT(GSI_EV_CTRL);
-
 	/* Each IEOB interrupt is enabled (later) as needed by channels */
 	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
 	gsi->type_enabled_bitmap |= BIT(GSI_IEOB);
@@ -320,7 +317,6 @@ static void gsi_irq_disable(struct gsi *gsi)
 	iowrite32(0, gsi->virt + GSI_CNTXT_GSI_IRQ_EN_OFFSET);
 	iowrite32(0, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
 	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_IEOB_IRQ_MSK_OFFSET);
-	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
 }
 
 /* Return the virtual address associated with a ring index */
@@ -374,13 +370,30 @@ static int evt_ring_command(struct gsi *gsi, u32 evt_ring_id,
 	struct gsi_evt_ring *evt_ring = &gsi->evt_ring[evt_ring_id];
 	struct completion *completion = &evt_ring->completion;
 	struct device *dev = gsi->dev;
+	bool success;
 	u32 val;
 
+	/* We only perform one event ring command at a time, and event
+	 * control interrupts should only occur when such a command
+	 * is issued here.  Only permit *this* event ring to trigger
+	 * an interrupt, and only enable the event control IRQ type
+	 * when we expect it to occur.
+	 */
+	val = BIT(evt_ring_id);
+	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
+	gsi_irq_type_enable(gsi, GSI_EV_CTRL);
+
 	val = u32_encode_bits(evt_ring_id, EV_CHID_FMASK);
 	val |= u32_encode_bits(opcode, EV_OPCODE_FMASK);
 
-	if (gsi_command(gsi, GSI_EV_CH_CMD_OFFSET, val, completion))
-		return 0;	/* Success! */
+	success = gsi_command(gsi, GSI_EV_CH_CMD_OFFSET, val, completion);
+
+	/* Disable the interrupt again */
+	gsi_irq_type_disable(gsi, GSI_EV_CTRL);
+	iowrite32(0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_MSK_OFFSET);
+
+	if (success)
+		return 0;
 
 	dev_err(dev, "GSI command %u for event ring %u timed out, state %u\n",
 		opcode, evt_ring_id, evt_ring->state);
-- 
2.20.1