Merge branch 'net-ipa-gsi-channel-flow-control'

Alex Elder says:

====================
net: ipa: GSI channel flow control

Starting with IPA v4.2, endpoint DELAY mode (which prevents data
transfer on TX endpoints) does not work properly.  To address this,
changes were made to allow underlying GSI channels to be put into
a "flow controlled" state, which achieves a similar objective.
The first patch in this series implements the flow controlled
channel state and the commands used to control it.  It arranges
to use the new mechanism--instead of DELAY mode--for IPA v4.2+.

In IPA v4.11, the notion of GSI channel flow control was enhanced,
and implemented in a slightly different way.  For the most part this
doesn't affect the way the IPA driver uses flow control, but the
second patch adds support for the newer mechanism.
====================

Link: https://lore.kernel.org/r/20211124194416.707007-1-elder@linaro.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

4 files changed, 99 insertions, 35 deletions

diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index b611e39167fe..bc981043cc80 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -93,6 +93,7 @@
 
 #define GSI_CHANNEL_STOP_RETRIES	10
 #define GSI_CHANNEL_MODEM_HALT_RETRIES	10
+#define GSI_CHANNEL_MODEM_FLOW_RETRIES	5	/* disable flow control only */
 
 #define GSI_MHI_EVENT_ID_START		10	/* 1st reserved event id */
 #define GSI_MHI_EVENT_ID_END		16	/* Last reserved event id */
@@ -1162,18 +1163,23 @@ static void gsi_isr_gp_int1(struct gsi *gsi)
 	u32 result;
 	u32 val;
 
-	/* This interrupt is used to handle completions of the two GENERIC
-	 * GSI commands.  We use these to allocate and halt channels on
-	 * the modem's behalf due to a hardware quirk on IPA v4.2.  Once
-	 * allocated, the modem "owns" these channels, and as a result we
-	 * have no way of knowing the channel's state at any given time.
+	/* This interrupt is used to handle completions of GENERIC GSI
+	 * commands.  We use these to allocate and halt channels on the
+	 * modem's behalf due to a hardware quirk on IPA v4.2.  The modem
+	 * "owns" channels even when the AP allocates them, and have no
+	 * way of knowing whether a modem channel's state has been changed.
+	 *
+	 * We also use GENERIC commands to enable/disable channel flow
+	 * control for IPA v4.2+.
 	 *
 	 * It is recommended that we halt the modem channels we allocated
 	 * when shutting down, but it's possible the channel isn't running
 	 * at the time we issue the HALT command.  We'll get an error in
 	 * that case, but it's harmless (the channel is already halted).
+	 * Similarly, we could get an error back when updating flow control
+	 * on a channel because it's not in the proper state.
 	 *
-	 * For this reason, we silently ignore a CHANNEL_NOT_RUNNING error
+	 * In either case, we silently ignore a CHANNEL_NOT_RUNNING error
 	 * if we receive it.
 	 */
 	val = ioread32(gsi->virt + GSI_CNTXT_SCRATCH_0_OFFSET);
@@ -1639,18 +1645,25 @@ static void gsi_channel_teardown_one(struct gsi *gsi, u32 channel_id)
 	gsi_evt_ring_de_alloc_command(gsi, evt_ring_id);
 }
 
+/* We use generic commands only to operate on modem channels.  We don't have
+ * the ability to determine channel state for a modem channel, so we simply
+ * issue the command and wait for it to complete.
+ */
 static int gsi_generic_command(struct gsi *gsi, u32 channel_id,
-			       enum gsi_generic_cmd_opcode opcode)
+			       enum gsi_generic_cmd_opcode opcode,
+			       u8 params)
 {
 	bool timeout;
 	u32 val;
 
-	/* The error global interrupt type is always enabled (until we
-	 * teardown), so we won't change that.  A generic EE command
-	 * completes with a GSI global interrupt of type GP_INT1.  We
-	 * only perform one generic command at a time (to allocate or
-	 * halt a modem channel) and only from this function.  So we
-	 * enable the GP_INT1 IRQ type here while we're expecting it.
+	/* The error global interrupt type is always enabled (until we tear
+	 * down), so we will keep it enabled.
+	 *
+	 * A generic EE command completes with a GSI global interrupt of
+	 * type GP_INT1.  We only perform one generic command at a time
+	 * (to allocate, halt, or enable/disable flow control on a modem
+	 * channel), and only from this function.  So we enable the GP_INT1
+	 * IRQ type here, and disable it again after the command completes.
 	 */
 	val = BIT(ERROR_INT) | BIT(GP_INT1);
 	iowrite32(val, gsi->virt + GSI_CNTXT_GLOB_IRQ_EN_OFFSET);
@@ -1664,6 +1677,7 @@ static int gsi_generic_command(struct gsi *gsi, u32 channel_id,
 	val = u32_encode_bits(opcode, GENERIC_OPCODE_FMASK);
 	val |= u32_encode_bits(channel_id, GENERIC_CHID_FMASK);
 	val |= u32_encode_bits(GSI_EE_MODEM, GENERIC_EE_FMASK);
+	val |= u32_encode_bits(params, GENERIC_PARAMS_FMASK);
 
 	timeout = !gsi_command(gsi, GSI_GENERIC_CMD_OFFSET, val);
 
@@ -1682,7 +1696,7 @@ static int gsi_generic_command(struct gsi *gsi, u32 channel_id,
 static int gsi_modem_channel_alloc(struct gsi *gsi, u32 channel_id)
 {
 	return gsi_generic_command(gsi, channel_id,
-				   GSI_GENERIC_ALLOCATE_CHANNEL);
+				   GSI_GENERIC_ALLOCATE_CHANNEL, 0);
 }
 
 static void gsi_modem_channel_halt(struct gsi *gsi, u32 channel_id)
@@ -1692,7 +1706,7 @@ static void gsi_modem_channel_halt(struct gsi *gsi, u32 channel_id)
 
 	do
 		ret = gsi_generic_command(gsi, channel_id,
-					  GSI_GENERIC_HALT_CHANNEL);
+					  GSI_GENERIC_HALT_CHANNEL, 0);
 	while (ret == -EAGAIN && retries--);
 
 	if (ret)
@@ -1700,6 +1714,32 @@ static void gsi_modem_channel_halt(struct gsi *gsi, u32 channel_id)
 			ret, channel_id);
 }
 
+/* Enable or disable flow control for a modem GSI TX channel (IPA v4.2+) */
+void
+gsi_modem_channel_flow_control(struct gsi *gsi, u32 channel_id, bool enable)
+{
+	u32 retries = 0;
+	u32 command;
+	int ret;
+
+	command = enable ? GSI_GENERIC_ENABLE_FLOW_CONTROL
+			 : GSI_GENERIC_DISABLE_FLOW_CONTROL;
+	/* Disabling flow control on IPA v4.11+ can return -EAGAIN if enable
+	 * is underway.  In this case we need to retry the command.
+	 */
+	if (!enable && gsi->version >= IPA_VERSION_4_11)
+		retries = GSI_CHANNEL_MODEM_FLOW_RETRIES;
+
+	do
+		ret = gsi_generic_command(gsi, channel_id, command, 0);
+	while (ret == -EAGAIN && retries--);
+
+	if (ret)
+		dev_err(gsi->dev,
+			"error %d %sabling mode channel %u flow control\n",
+			ret, enable ? "en" : "dis", channel_id);
+}
+
 /* Setup function for channels */
 static int gsi_channel_setup(struct gsi *gsi)
 {
diff --git a/drivers/net/ipa/gsi.h b/drivers/net/ipa/gsi.h
index 75dfc7655f3b..9cc657658811 100644
--- a/drivers/net/ipa/gsi.h
+++ b/drivers/net/ipa/gsi.h
@@ -101,6 +101,7 @@ enum gsi_channel_state {
 	GSI_CHANNEL_STATE_STARTED		= 0x2,
 	GSI_CHANNEL_STATE_STOPPED		= 0x3,
 	GSI_CHANNEL_STATE_STOP_IN_PROC		= 0x4,
+	GSI_CHANNEL_STATE_FLOW_CONTROLLED	= 0x5,	/* IPA v4.2-v4.9 */
 	GSI_CHANNEL_STATE_ERROR			= 0xf,
 };
 
@@ -216,6 +217,15 @@ int gsi_channel_start(struct gsi *gsi, u32 channel_id);
 int gsi_channel_stop(struct gsi *gsi, u32 channel_id);
 
 /**
+ * gsi_modem_channel_flow_control() - Set channel flow control state (IPA v4.2+)
+ * @gsi:	GSI pointer returned by gsi_setup()
+ * @channel_id:	Modem TX channel to control
+ * @enable:	Whether to enable flow control (i.e., prevent flow)
+ */
+void gsi_modem_channel_flow_control(struct gsi *gsi, u32 channel_id,
+				    bool enable);
+
+/**
  * gsi_channel_reset() - Reset an allocated GSI channel
  * @gsi:	GSI pointer
  * @channel_id:	Channel to be reset
diff --git a/drivers/net/ipa/gsi_reg.h b/drivers/net/ipa/gsi_reg.h
index bf9593d9eaea..8906f4381032 100644
--- a/drivers/net/ipa/gsi_reg.h
+++ b/drivers/net/ipa/gsi_reg.h
@@ -313,11 +313,15 @@ enum gsi_evt_cmd_opcode {
 #define GENERIC_OPCODE_FMASK		GENMASK(4, 0)
 #define GENERIC_CHID_FMASK		GENMASK(9, 5)
 #define GENERIC_EE_FMASK		GENMASK(13, 10)
+#define GENERIC_PARAMS_FMASK		GENMASK(31, 24)	/* IPA v4.11+ */
 
 /** enum gsi_generic_cmd_opcode - GENERIC_OPCODE field values in GENERIC_CMD */
 enum gsi_generic_cmd_opcode {
 	GSI_GENERIC_HALT_CHANNEL		= 0x1,
 	GSI_GENERIC_ALLOCATE_CHANNEL		= 0x2,
+	GSI_GENERIC_ENABLE_FLOW_CONTROL		= 0x3,	/* IPA v4.2+ */
+	GSI_GENERIC_DISABLE_FLOW_CONTROL	= 0x4,	/* IPA v4.2+ */
+	GSI_GENERIC_QUERY_FLOW_CONTROL		= 0x5,	/* IPA v4.11+ */
 };
 
 /* The next register is present for IPA v3.5.1 and above */
diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index fba576a7717f..b475f89e09bd 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -237,7 +237,8 @@ static struct gsi_trans *ipa_endpoint_trans_alloc(struct ipa_endpoint *endpoint,
 }
 
 /* suspend_delay represents suspend for RX, delay for TX endpoints.
- * Note that suspend is not supported starting with IPA v4.0.
+ * Note that suspend is not supported starting with IPA v4.0, and
+ * delay mode should not be used starting with IPA v4.2.
  */
 static bool
 ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
@@ -248,11 +249,8 @@ ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
 	u32 mask;
 	u32 val;
 
-	/* Suspend is not supported for IPA v4.0+.  Delay doesn't work
-	 * correctly on IPA v4.2.
-	 */
 	if (endpoint->toward_ipa)
-		WARN_ON(ipa->version == IPA_VERSION_4_2);
+		WARN_ON(ipa->version >= IPA_VERSION_4_2);
 	else
 		WARN_ON(ipa->version >= IPA_VERSION_4_0);
 
@@ -270,15 +268,15 @@ ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
 	return state;
 }
 
-/* We currently don't care what the previous state was for delay mode */
+/* We don't care what the previous state was for delay mode */
 static void
 ipa_endpoint_program_delay(struct ipa_endpoint *endpoint, bool enable)
 {
+	/* Delay mode should not be used for IPA v4.2+ */
+	WARN_ON(endpoint->ipa->version >= IPA_VERSION_4_2);
 	WARN_ON(!endpoint->toward_ipa);
 
-	/* Delay mode doesn't work properly for IPA v4.2 */
-	if (endpoint->ipa->version != IPA_VERSION_4_2)
-		(void)ipa_endpoint_init_ctrl(endpoint, enable);
+	(void)ipa_endpoint_init_ctrl(endpoint, enable);
 }
 
 static bool ipa_endpoint_aggr_active(struct ipa_endpoint *endpoint)
@@ -355,26 +353,29 @@ ipa_endpoint_program_suspend(struct ipa_endpoint *endpoint, bool enable)
 	return suspended;
 }
 
-/* Enable or disable delay or suspend mode on all modem endpoints */
+/* Put all modem RX endpoints into suspend mode, and stop transmission
+ * on all modem TX endpoints.  Prior to IPA v4.2, endpoint DELAY mode is
+ * used for TX endpoints; starting with IPA v4.2 we use GSI channel flow
+ * control instead.
+ */
 void ipa_endpoint_modem_pause_all(struct ipa *ipa, bool enable)
 {
 	u32 endpoint_id;
 
-	/* DELAY mode doesn't work correctly on IPA v4.2 */
-	if (ipa->version == IPA_VERSION_4_2)
-		return;
-
 	for (endpoint_id = 0; endpoint_id < IPA_ENDPOINT_MAX; endpoint_id++) {
 		struct ipa_endpoint *endpoint = &ipa->endpoint[endpoint_id];
 
 		if (endpoint->ee_id != GSI_EE_MODEM)
 			continue;
 
-		/* Set TX delay mode or RX suspend mode */
-		if (endpoint->toward_ipa)
+		if (!endpoint->toward_ipa)
+			(void)ipa_endpoint_program_suspend(endpoint, enable);
+		else if (ipa->version < IPA_VERSION_4_2)
 			ipa_endpoint_program_delay(endpoint, enable);
 		else
-			(void)ipa_endpoint_program_suspend(endpoint, enable);
+			gsi_modem_channel_flow_control(&ipa->gsi,
+						       endpoint->channel_id,
+						       enable);
 	}
 }
 
@@ -1532,10 +1533,19 @@ static void ipa_endpoint_reset(struct ipa_endpoint *endpoint)
 
 static void ipa_endpoint_program(struct ipa_endpoint *endpoint)
 {
-	if (endpoint->toward_ipa)
-		ipa_endpoint_program_delay(endpoint, false);
-	else
+	if (endpoint->toward_ipa) {
+		/* Newer versions of IPA use GSI channel flow control
+		 * instead of endpoint DELAY mode to prevent sending data.
+		 * Flow control is disabled for newly-allocated channels,
+		 * and we can assume flow control is not (ever) enabled
+		 * for AP TX channels.
+		 */
+		if (endpoint->ipa->version < IPA_VERSION_4_2)
+			ipa_endpoint_program_delay(endpoint, false);
+	} else {
+		/* Ensure suspend mode is off on all AP RX endpoints */
 		(void)ipa_endpoint_program_suspend(endpoint, false);
+	}
 	ipa_endpoint_init_cfg(endpoint);
 	ipa_endpoint_init_nat(endpoint);
 	ipa_endpoint_init_hdr(endpoint);