[PATCH net 1/3] net: ipa: clear pending interrupts before enabling

[Alex Elder]

We enable the completion interrupt for channel or event ring
commands only when we issue them.  The interrupt is disabled after
the interrupt has fired, or after we have timed out waiting for it.

If we time out, the command could complete after the interrupt has
been disabled, causing a state change in the channel or event ring.
The interrupt associated with that state change would be delivered
the next time the completion interrupt is enabled.

To avoid previous command completions interfering with new commands,
clear all pending completion interrupts before re-enabling them for
a new command.

Fixes: b4175f8731f78 ("net: ipa: only enable GSI event control IRQs when needed")
Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
---
 drivers/net/ipa/gsi.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index c4795249719d4..4aee60d62ab09 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -340,7 +340,13 @@ static int evt_ring_command(struct gsi *gsi, u32 evt_ring_id,
 	 * 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.
+	 *
+	 * There's a small chance that a previous command completed
+	 * after the interrupt was disabled, so make sure we have no
+	 * pending interrupts before we enable them.
 	 */
+	iowrite32(~0, gsi->virt + GSI_CNTXT_SRC_EV_CH_IRQ_CLR_OFFSET);
+
 	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);
@@ -453,7 +459,13 @@ gsi_channel_command(struct gsi_channel *channel, enum gsi_ch_cmd_opcode opcode)
 	 * issued here.  So we only permit *this* channel to trigger
 	 * an interrupt and only enable the channel control IRQ type
 	 * when we expect it to occur.
+	 *
+	 * There's a small chance that a previous command completed
+	 * after the interrupt was disabled, so make sure we have no
+	 * pending interrupts before we enable them.
 	 */
+	iowrite32(~0, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_CLR_OFFSET);
+
 	val = BIT(channel_id);
 	iowrite32(val, gsi->virt + GSI_CNTXT_SRC_CH_IRQ_MSK_OFFSET);
 	gsi_irq_type_enable(gsi, GSI_CH_CTRL);
-- 
2.20.1