[PATCH net-next 0/3] net: ipa: kill endpoint delay mode workaround

[PATCH net-next 0/3] net: ipa: kill endpoint delay mode workaround

[Alex Elder]

A "delay mode" feature was put in place to work around a problem
where packets could passed to the modem before it was ready to
handle them.  That problem no longer exists, and we don't need the
workaround any more so get rid of it.

					-Alex

Alex Elder (3):
  net: ipa: have ipa_endpoint_init_ctrl() return previous state
  net: ipa: introduce ipa_endpoint_program_suspend()
  net: ipa: remove endpoint delay mode feature

 drivers/net/ipa/ipa_data-sdm845.c |  1 -
 drivers/net/ipa/ipa_data.h        |  6 ---
 drivers/net/ipa/ipa_endpoint.c    | 85 ++++++++++++++++++-------------
 3 files changed, 49 insertions(+), 43 deletions(-)

-- 
2.20.1

[PATCH net-next 1/3] net: ipa: have ipa_endpoint_init_ctrl() return previous state

[Alex Elder]

Change ipa_endpoint_init_ctrl() so it returns the previous state
(whether suspend or delay mode was enabled) rather than indicating
whether the request caused a change in state.  This makes it easier
to understand what's happening where called.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_endpoint.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index 6de03be28784..ad72adff653e 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -284,11 +284,12 @@ 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.
  */
-static int
+static bool
 ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
 {
 	u32 offset = IPA_REG_ENDP_INIT_CTRL_N_OFFSET(endpoint->endpoint_id);
 	struct ipa *ipa = endpoint->ipa;
+	bool state;
 	u32 mask;
 	u32 val;
 
@@ -296,13 +297,14 @@ ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
 	mask = endpoint->toward_ipa ? ENDP_DELAY_FMASK : ENDP_SUSPEND_FMASK;
 
 	val = ioread32(ipa->reg_virt + offset);
-	if (suspend_delay == !!(val & mask))
-		return -EALREADY;	/* Already set to desired state */
+	/* Don't bother if it's already in the requested state */
+	state = !!(val & mask);
+	if (suspend_delay != state) {
+		val ^= mask;
+		iowrite32(val, ipa->reg_virt + offset);
+	}
 
-	val ^= mask;
-	iowrite32(val, ipa->reg_virt + offset);
-
-	return 0;
+	return state;
 }
 
 /* Enable or disable delay or suspend mode on all modem endpoints */
@@ -1164,8 +1166,7 @@ static int ipa_endpoint_reset_rx_aggr(struct ipa_endpoint *endpoint)
 
 	/* Make sure the channel isn't suspended */
 	if (endpoint->ipa->version == IPA_VERSION_3_5_1)
-		if (!ipa_endpoint_init_ctrl(endpoint, false))
-			endpoint_suspended = true;
+		endpoint_suspended = ipa_endpoint_init_ctrl(endpoint, false);
 
 	/* Start channel and do a 1 byte read */
 	ret = gsi_channel_start(gsi, endpoint->channel_id);
@@ -1318,21 +1319,20 @@ static void ipa_endpoint_program(struct ipa_endpoint *endpoint)
 	if (endpoint->toward_ipa) {
 		bool delay_mode = endpoint->data->tx.delay;
 
-		ret = ipa_endpoint_init_ctrl(endpoint, delay_mode);
 		/* Endpoint is expected to not be in delay mode */
-		if (!ret != delay_mode) {
+		if (ipa_endpoint_init_ctrl(endpoint, delay_mode))
 			dev_warn(dev,
 				"TX endpoint %u was %sin delay mode\n",
 				endpoint->endpoint_id,
 				delay_mode ? "already " : "");
-		}
 		ipa_endpoint_init_hdr_ext(endpoint);
 		ipa_endpoint_init_aggr(endpoint);
 		ipa_endpoint_init_deaggr(endpoint);
 		ipa_endpoint_init_seq(endpoint);
 	} else {
+		/* Endpoint is expected to not be suspended */
 		if (endpoint->ipa->version == IPA_VERSION_3_5_1) {
-			if (!ipa_endpoint_init_ctrl(endpoint, false))
+			if (ipa_endpoint_init_ctrl(endpoint, false))
 				dev_warn(dev,
 					"RX endpoint %u was suspended\n",
 					endpoint->endpoint_id);
@@ -1471,7 +1471,7 @@ void ipa_endpoint_resume_one(struct ipa_endpoint *endpoint)
 	/* IPA v3.5.1 doesn't use channel start for resume */
 	start_channel = endpoint->ipa->version != IPA_VERSION_3_5_1;
 	if (!endpoint->toward_ipa && !start_channel)
-		WARN_ON(ipa_endpoint_init_ctrl(endpoint, false));
+		WARN_ON(!ipa_endpoint_init_ctrl(endpoint, false));
 
 	ret = gsi_channel_resume(gsi, endpoint->channel_id, start_channel);
 	if (ret)
-- 
2.20.1

[PATCH net-next 2/3] net: ipa: introduce ipa_endpoint_program_suspend()

[Alex Elder]

Create a new helper function that encapsulates enabling or disabling
suspend on an RX endpoint.  It returns the previous state of the
endpoint (true means suspend mode was enabled).

Create another function that handles enabling or disabling delay mode
on a TX endpoint.  Delay mode does not work correctly on IPA version
4.2, so we don't currently use it (and shouldn't).

We only set delay mode in one case, and although we don't expect an
endpoint to already be in delay mode, it doesn't really matter if it
was.  So the delay function doesn't return a value.

Stop issuing warnings if the previous suspend or delay mode state
differs from what is expected.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_endpoint.c | 67 +++++++++++++++++++++-------------
 1 file changed, 41 insertions(+), 26 deletions(-)

diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index ad72adff653e..a830101b8edb 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -293,7 +293,14 @@ ipa_endpoint_init_ctrl(struct ipa_endpoint *endpoint, bool suspend_delay)
 	u32 mask;
 	u32 val;
 
-	/* assert(ipa->version == IPA_VERSION_3_5_1 */
+	/* Suspend is not supported for IPA v4.0+.  Delay doesn't work
+	 * correctly on IPA v4.2.
+	 *
+	 * if (endpoint->toward_ipa)
+	 * 	assert(ipa->version != IPA_VERSION_4.2);
+	 * else
+	 * 	assert(ipa->version == IPA_VERSION_3_5_1);
+	 */
 	mask = endpoint->toward_ipa ? ENDP_DELAY_FMASK : ENDP_SUSPEND_FMASK;
 
 	val = ioread32(ipa->reg_virt + offset);
@@ -307,13 +314,31 @@ 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 */
+static void
+ipa_endpoint_program_delay(struct ipa_endpoint *endpoint, bool enable)
+{
+	/* assert(endpoint->toward_ipa); */
+
+	(void)ipa_endpoint_init_ctrl(endpoint, enable);
+}
+
+/* Returns previous suspend state (true means it was enabled) */
+static bool
+ipa_endpoint_program_suspend(struct ipa_endpoint *endpoint, bool enable)
+{
+	/* assert(!endpoint->toward_ipa); */
+
+	return ipa_endpoint_init_ctrl(endpoint, enable);
+}
+
 /* Enable or disable delay or suspend mode on all modem endpoints */
 void ipa_endpoint_modem_pause_all(struct ipa *ipa, bool enable)
 {
 	bool support_suspend;
 	u32 endpoint_id;
 
-	/* DELAY mode doesn't work right on IPA v4.2 */
+	/* DELAY mode doesn't work correctly on IPA v4.2 */
 	if (ipa->version == IPA_VERSION_4_2)
 		return;
 
@@ -327,8 +352,10 @@ void ipa_endpoint_modem_pause_all(struct ipa *ipa, bool enable)
 			continue;
 
 		/* Set TX delay mode, or for IPA v3.5.1 RX suspend mode */
-		if (endpoint->toward_ipa || support_suspend)
-			(void)ipa_endpoint_init_ctrl(endpoint, enable);
+		if (endpoint->toward_ipa)
+			ipa_endpoint_program_delay(endpoint, enable);
+		else if (support_suspend)
+			(void)ipa_endpoint_program_suspend(endpoint, enable);
 	}
 }
 
@@ -1135,8 +1162,8 @@ static int ipa_endpoint_reset_rx_aggr(struct ipa_endpoint *endpoint)
 {
 	struct device *dev = &endpoint->ipa->pdev->dev;
 	struct ipa *ipa = endpoint->ipa;
-	bool endpoint_suspended = false;
 	struct gsi *gsi = &ipa->gsi;
+	bool suspended = false;
 	dma_addr_t addr;
 	bool db_enable;
 	u32 retries;
@@ -1166,7 +1193,7 @@ static int ipa_endpoint_reset_rx_aggr(struct ipa_endpoint *endpoint)
 
 	/* Make sure the channel isn't suspended */
 	if (endpoint->ipa->version == IPA_VERSION_3_5_1)
-		endpoint_suspended = ipa_endpoint_init_ctrl(endpoint, false);
+		suspended = ipa_endpoint_program_suspend(endpoint, false);
 
 	/* Start channel and do a 1 byte read */
 	ret = gsi_channel_start(gsi, endpoint->channel_id);
@@ -1211,8 +1238,8 @@ static int ipa_endpoint_reset_rx_aggr(struct ipa_endpoint *endpoint)
 err_endpoint_stop:
 	ipa_endpoint_stop(endpoint);
 out_suspend_again:
-	if (endpoint_suspended)
-		(void)ipa_endpoint_init_ctrl(endpoint, true);
+	if (suspended)
+		(void)ipa_endpoint_program_suspend(endpoint, true);
 	dma_unmap_single(dev, addr, len, DMA_FROM_DEVICE);
 out_kfree:
 	kfree(virt);
@@ -1313,30 +1340,18 @@ int ipa_endpoint_stop(struct ipa_endpoint *endpoint)
 
 static void ipa_endpoint_program(struct ipa_endpoint *endpoint)
 {
-	struct device *dev = &endpoint->ipa->pdev->dev;
-	int ret;
-
 	if (endpoint->toward_ipa) {
 		bool delay_mode = endpoint->data->tx.delay;
 
-		/* Endpoint is expected to not be in delay mode */
-		if (ipa_endpoint_init_ctrl(endpoint, delay_mode))
-			dev_warn(dev,
-				"TX endpoint %u was %sin delay mode\n",
-				endpoint->endpoint_id,
-				delay_mode ? "already " : "");
+		if (endpoint->ipa->version != IPA_VERSION_4_2)
+			ipa_endpoint_program_delay(endpoint, delay_mode);
 		ipa_endpoint_init_hdr_ext(endpoint);
 		ipa_endpoint_init_aggr(endpoint);
 		ipa_endpoint_init_deaggr(endpoint);
 		ipa_endpoint_init_seq(endpoint);
 	} else {
-		/* Endpoint is expected to not be suspended */
-		if (endpoint->ipa->version == IPA_VERSION_3_5_1) {
-			if (ipa_endpoint_init_ctrl(endpoint, false))
-				dev_warn(dev,
-					"RX endpoint %u was suspended\n",
-					endpoint->endpoint_id);
-		}
+		if (endpoint->ipa->version == IPA_VERSION_3_5_1)
+			(void)ipa_endpoint_program_suspend(endpoint, false);
 		ipa_endpoint_init_hdr_ext(endpoint);
 		ipa_endpoint_init_aggr(endpoint);
 	}
@@ -1448,7 +1463,7 @@ void ipa_endpoint_suspend_one(struct ipa_endpoint *endpoint)
 		 * aggregation frame, then simulating the arrival of such
 		 * an interrupt.
 		 */
-		WARN_ON(ipa_endpoint_init_ctrl(endpoint, true));
+		(void)ipa_endpoint_program_suspend(endpoint, true);
 		ipa_endpoint_suspend_aggr(endpoint);
 	}
 
@@ -1471,7 +1486,7 @@ void ipa_endpoint_resume_one(struct ipa_endpoint *endpoint)
 	/* IPA v3.5.1 doesn't use channel start for resume */
 	start_channel = endpoint->ipa->version != IPA_VERSION_3_5_1;
 	if (!endpoint->toward_ipa && !start_channel)
-		WARN_ON(!ipa_endpoint_init_ctrl(endpoint, false));
+		(void)ipa_endpoint_program_suspend(endpoint, false);
 
 	ret = gsi_channel_resume(gsi, endpoint->channel_id, start_channel);
 	if (ret)
-- 
2.20.1

[PATCH net-next 3/3] net: ipa: remove endpoint delay mode feature

[Alex Elder]

A "delay mode" feature was put in place to work around a problem
that was observed during development of the upstream IPA driver.  It
used TX endpoint "delay mode" in order to prevent transmitting
packets toward the modem before it was ready.

A race condition that would explain the problem has long since been
fixed, and we have concluded that the "delay mode" feature is no
longer required.  So get rid of it.

Signed-off-by: Alex Elder <elder@linaro.org>
---
 drivers/net/ipa/ipa_data-sdm845.c | 1 -
 drivers/net/ipa/ipa_data.h        | 6 ------
 drivers/net/ipa/ipa_endpoint.c    | 4 +---
 3 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/net/ipa/ipa_data-sdm845.c b/drivers/net/ipa/ipa_data-sdm845.c
index f7ba85717edf..52d4b84e0dac 100644
--- a/drivers/net/ipa/ipa_data-sdm845.c
+++ b/drivers/net/ipa/ipa_data-sdm845.c
@@ -74,7 +74,6 @@ static const struct ipa_gsi_endpoint_data ipa_gsi_endpoint_data[] = {
 				.tx = {
 					.status_endpoint =
 						IPA_ENDPOINT_MODEM_AP_RX,
-					.delay	= true,
 				},
 			},
 		},
diff --git a/drivers/net/ipa/ipa_data.h b/drivers/net/ipa/ipa_data.h
index 16dfd74717b1..7fc1058a5ca9 100644
--- a/drivers/net/ipa/ipa_data.h
+++ b/drivers/net/ipa/ipa_data.h
@@ -80,18 +80,12 @@ struct gsi_channel_data {
 /**
  * struct ipa_endpoint_tx_data - configuration data for TX endpoints
  * @status_endpoint:	endpoint to which status elements are sent
- * @delay:		whether endpoint starts in delay mode
- *
- * Delay mode prevents a TX endpoint from transmitting anything, even if
- * commands have been presented to the hardware.  Once the endpoint exits
- * delay mode, queued transfer commands are sent.
  *
  * The @status_endpoint is only valid if the endpoint's @status_enable
  * flag is set.
  */
 struct ipa_endpoint_tx_data {
 	enum ipa_endpoint_name status_endpoint;
-	bool delay;
 };
 
 /**
diff --git a/drivers/net/ipa/ipa_endpoint.c b/drivers/net/ipa/ipa_endpoint.c
index a830101b8edb..8dc12ec18fc7 100644
--- a/drivers/net/ipa/ipa_endpoint.c
+++ b/drivers/net/ipa/ipa_endpoint.c
@@ -1341,10 +1341,8 @@ int ipa_endpoint_stop(struct ipa_endpoint *endpoint)
 static void ipa_endpoint_program(struct ipa_endpoint *endpoint)
 {
 	if (endpoint->toward_ipa) {
-		bool delay_mode = endpoint->data->tx.delay;
-
 		if (endpoint->ipa->version != IPA_VERSION_4_2)
-			ipa_endpoint_program_delay(endpoint, delay_mode);
+			ipa_endpoint_program_delay(endpoint, false);
 		ipa_endpoint_init_hdr_ext(endpoint);
 		ipa_endpoint_init_aggr(endpoint);
 		ipa_endpoint_init_deaggr(endpoint);
-- 
2.20.1

Re: [PATCH net-next 0/3] net: ipa: kill endpoint delay mode workaround

[David Miller]

From: Alex Elder <elder@linaro.org>
Date: Mon,  4 May 2020 18:37:10 -0500

> A "delay mode" feature was put in place to work around a problem
> where packets could passed to the modem before it was ready to
> handle them.  That problem no longer exists, and we don't need the
> workaround any more so get rid of it.

Series applied.