Merge branch 'net-ipa-gsi-interrupt-handling-fixes'

Alex Elder says:

====================
net: ipa: GSI interrupt handling fixes

This series implements fixes for some issues related to handling
interrupts when GSI channel and event ring commands complete.

The first issue is that the completion condition for an event ring
or channel command could occur while the associated interrupt is
disabled.  This would cause the interrupt to fire when it is
subsequently enabled, even if the condition it signals had already
been handled.  The fix is to clear any pending interrupt conditions
before re-enabling the interrupt.

The second and third patches change how the success of an event ring
or channel command is determined.  These commands change the state
of an event ring or channel.  Previously the receipt of a completion
interrupt was required to consider a command successful.  Instead, a
command is successful if it changes the state of the target event
ring or channel in the way expected.  This way the command can
succeed even if the completion interrupt did not arrive while it was
enabled.
====================

Link: https://lore.kernel.org/r/20201222180012.22489-1-elder@linaro.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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);
@@ -378,13 +384,15 @@ static int gsi_evt_ring_alloc_command(struct gsi *gsi, u32 evt_ring_id)
 	}
 
 	ret = evt_ring_command(gsi, evt_ring_id, GSI_EVT_ALLOCATE);
-	if (!ret && evt_ring->state != GSI_EVT_RING_STATE_ALLOCATED) {
+
+	/* If successful the event ring state will have changed */
+	if (evt_ring->state == GSI_EVT_RING_STATE_ALLOCATED)
+		return 0;
+
 	dev_err(gsi->dev, "event ring %u bad state %u after alloc\n",
 		evt_ring_id, evt_ring->state);
-		ret = -EIO;
-	}
 
-	return ret;
+	return -EIO;
 }
 
 /* Reset a GSI event ring in ALLOCATED or ERROR state. */
@@ -402,7 +410,11 @@ static void gsi_evt_ring_reset_command(struct gsi *gsi, u32 evt_ring_id)
 	}
 
 	ret = evt_ring_command(gsi, evt_ring_id, GSI_EVT_RESET);
-	if (!ret && evt_ring->state != GSI_EVT_RING_STATE_ALLOCATED)
+
+	/* If successful the event ring state will have changed */
+	if (evt_ring->state == GSI_EVT_RING_STATE_ALLOCATED)
+		return;
+
 	dev_err(gsi->dev, "event ring %u bad state %u after reset\n",
 		evt_ring_id, evt_ring->state);
 }
@@ -420,7 +432,11 @@ static void gsi_evt_ring_de_alloc_command(struct gsi *gsi, u32 evt_ring_id)
 	}
 
 	ret = evt_ring_command(gsi, evt_ring_id, GSI_EVT_DE_ALLOC);
-	if (!ret && evt_ring->state != GSI_EVT_RING_STATE_NOT_ALLOCATED)
+
+	/* If successful the event ring state will have changed */
+	if (evt_ring->state == GSI_EVT_RING_STATE_NOT_ALLOCATED)
+		return;
+
 	dev_err(gsi->dev, "event ring %u bad state %u after dealloc\n",
 		evt_ring_id, evt_ring->state);
 }
@@ -453,7 +469,13 @@ 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);
@@ -493,15 +515,15 @@ static int gsi_channel_alloc_command(struct gsi *gsi, u32 channel_id)
 
 	ret = gsi_channel_command(channel, GSI_CH_ALLOCATE);
 
-	/* Channel state will normally have been updated */
+	/* If successful the channel state will have changed */
 	state = gsi_channel_state(channel);
-	if (!ret && state != GSI_CHANNEL_STATE_ALLOCATED) {
+	if (state == GSI_CHANNEL_STATE_ALLOCATED)
+		return 0;
+
 	dev_err(dev, "channel %u bad state %u after alloc\n",
 		channel_id, state);
-		ret = -EIO;
-	}
 
-	return ret;
+	return -EIO;
 }
 
 /* Start an ALLOCATED channel */
@@ -521,15 +543,15 @@ static int gsi_channel_start_command(struct gsi_channel *channel)
 
 	ret = gsi_channel_command(channel, GSI_CH_START);
 
-	/* Channel state will normally have been updated */
+	/* If successful the channel state will have changed */
 	state = gsi_channel_state(channel);
-	if (!ret && state != GSI_CHANNEL_STATE_STARTED) {
+	if (state == GSI_CHANNEL_STATE_STARTED)
+		return 0;
+
 	dev_err(dev, "channel %u bad state %u after start\n",
 		gsi_channel_id(channel), state);
-		ret = -EIO;
-	}
 
-	return ret;
+	return -EIO;
 }
 
 /* Stop a GSI channel in STARTED state */
@@ -556,10 +578,10 @@ static int gsi_channel_stop_command(struct gsi_channel *channel)
 
 	ret = gsi_channel_command(channel, GSI_CH_STOP);
 
-	/* Channel state will normally have been updated */
+	/* If successful the channel state will have changed */
 	state = gsi_channel_state(channel);
-	if (ret || state == GSI_CHANNEL_STATE_STOPPED)
-		return ret;
+	if (state == GSI_CHANNEL_STATE_STOPPED)
+		return 0;
 
 	/* We may have to try again if stop is in progress */
 	if (state == GSI_CHANNEL_STATE_STOP_IN_PROC)
@@ -592,9 +614,9 @@ static void gsi_channel_reset_command(struct gsi_channel *channel)
 
 	ret = gsi_channel_command(channel, GSI_CH_RESET);
 
-	/* Channel state will normally have been updated */
+	/* If successful the channel state will have changed */
 	state = gsi_channel_state(channel);
-	if (!ret && state != GSI_CHANNEL_STATE_ALLOCATED)
+	if (state != GSI_CHANNEL_STATE_ALLOCATED)
 		dev_err(dev, "channel %u bad state %u after reset\n",
 			gsi_channel_id(channel), state);
 }
@@ -616,9 +638,10 @@ static void gsi_channel_de_alloc_command(struct gsi *gsi, u32 channel_id)
 
 	ret = gsi_channel_command(channel, GSI_CH_DE_ALLOC);
 
-	/* Channel state will normally have been updated */
+	/* If successful the channel state will have changed */
 	state = gsi_channel_state(channel);
-	if (!ret && state != GSI_CHANNEL_STATE_NOT_ALLOCATED)
+
+	if (state != GSI_CHANNEL_STATE_NOT_ALLOCATED)
 		dev_err(dev, "channel %u bad state %u after dealloc\n",
 			channel_id, state);
 }