All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH v2 07/10] i2c: rcar: don't issue stop when HW does it automatically
@ 2015-11-12 14:42 ` Wolfram Sang
  0 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

The manual says (55.4.8.6) that HW does automatically send STOP after
NACK was received. My measuerments confirm that.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 316de40fa4dc69..3880293edc3c72 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -459,8 +459,8 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 
 	/* Nack */
 	if (msr & MNR) {
-		/* go to stop phase */
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
+		/* HW automatically sends STOP after received NACK */
+		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 		rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
 		rcar_i2c_flags_set(priv, ID_NACK);
 		goto out;
-- 
2.1.4


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH v2 07/10] i2c: rcar: don't issue stop when HW does it automatically
@ 2015-11-12 14:42 ` Wolfram Sang
  0 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

The manual says (55.4.8.6) that HW does automatically send STOP after
NACK was received. My measuerments confirm that.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 316de40fa4dc69..3880293edc3c72 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -459,8 +459,8 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 
 	/* Nack */
 	if (msr & MNR) {
-		/* go to stop phase */
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
+		/* HW automatically sends STOP after received NACK */
+		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 		rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
 		rcar_i2c_flags_set(priv, ID_NACK);
 		goto out;
-- 
2.1.4


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH v2 08/10] i2c: rcar: check master irqs before slave irqs
  2015-11-12 14:42 ` Wolfram Sang
@ 2015-11-12 14:42   ` Wolfram Sang
  -1 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

Due to the HW design, master IRQs are timing critical, so give them
precedence over slave IRQ.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 3880293edc3c72..8ad4c7d1ad8654 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -436,19 +436,17 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
 static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 {
 	struct rcar_i2c_priv *priv = ptr;
-	irqreturn_t result = IRQ_HANDLED;
 	u32 msr;
 
-	if (rcar_i2c_slave_irq(priv))
-		goto exit;
-
 	msr = rcar_i2c_read(priv, ICMSR);
 
 	/* Only handle interrupts that are currently enabled */
 	msr &= rcar_i2c_read(priv, ICMIER);
 	if (!msr) {
-		result = IRQ_NONE;
-		goto exit;
+		if (rcar_i2c_slave_irq(priv))
+			return IRQ_HANDLED;
+
+		return IRQ_NONE;
 	}
 
 	/* Arbitration lost */
@@ -485,8 +483,7 @@ out:
 		wake_up(&priv->wait);
 	}
 
-exit:
-	return result;
+	return IRQ_HANDLED;
 }
 
 static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
-- 
2.1.4


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH v2 08/10] i2c: rcar: check master irqs before slave irqs
@ 2015-11-12 14:42   ` Wolfram Sang
  0 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

Due to the HW design, master IRQs are timing critical, so give them
precedence over slave IRQ.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 3880293edc3c72..8ad4c7d1ad8654 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -436,19 +436,17 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
 static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 {
 	struct rcar_i2c_priv *priv = ptr;
-	irqreturn_t result = IRQ_HANDLED;
 	u32 msr;
 
-	if (rcar_i2c_slave_irq(priv))
-		goto exit;
-
 	msr = rcar_i2c_read(priv, ICMSR);
 
 	/* Only handle interrupts that are currently enabled */
 	msr &= rcar_i2c_read(priv, ICMIER);
 	if (!msr) {
-		result = IRQ_NONE;
-		goto exit;
+		if (rcar_i2c_slave_irq(priv))
+			return IRQ_HANDLED;
+
+		return IRQ_NONE;
 	}
 
 	/* Arbitration lost */
@@ -485,8 +483,7 @@ out:
 		wake_up(&priv->wait);
 	}
 
-exit:
-	return result;
+	return IRQ_HANDLED;
 }
 
 static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
-- 
2.1.4

^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH v2 09/10] i2c: rcar: revoke START request early
  2015-11-12 14:42 ` Wolfram Sang
@ 2015-11-12 14:42   ` Wolfram Sang
  -1 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

If we don't clear START generation as soon as possible, it may cause
another message to be generated, e.g. when receiving NACK in address
phase. To keep the race window as small as possible, we clear it right
at the beginning of the interrupt. We don't need any checks since we
always want to stop START and STOP generation on the next occasion after
we started it.

This patch improves the situation but sadly does not completely fix it.
It is still to be researched if we can do better given this HW design.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 8ad4c7d1ad8654..64a01c0177463a 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -83,6 +83,7 @@
 
 #define RCAR_BUS_PHASE_START	(MDBS | MIE | ESG)
 #define RCAR_BUS_PHASE_DATA	(MDBS | MIE)
+#define RCAR_BUS_MASK_DATA	(~(ESG | FSB) & 0xFF)
 #define RCAR_BUS_PHASE_STOP	(MDBS | MIE | FSB)
 
 #define RCAR_IRQ_SEND	(MNR | MAL | MST | MAT | MDE)
@@ -289,13 +290,6 @@ static int rcar_i2c_irq_send(struct rcar_i2c_priv *priv, u32 msr)
 	if (!(msr & MDE))
 		return 0;
 
-	/*
-	 * If address transfer phase finished,
-	 * goto data phase.
-	 */
-	if (msr & MAT)
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
-
 	if (priv->pos < msg->len) {
 		/*
 		 * Prepare next data to ICRXTX register.
@@ -347,11 +341,7 @@ static int rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
 		return 0;
 
 	if (msr & MAT) {
-		/*
-		 * Address transfer phase finished,
-		 * but, there is no data at this point.
-		 * Do nothing.
-		 */
+		/* Address transfer phase finished, but no data at this point. */
 	} else if (priv->pos < msg->len) {
 		/*
 		 * get received data
@@ -367,8 +357,6 @@ static int rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
 	 */
 	if (priv->pos + 1 >= msg->len)
 		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
-	else
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 
 	if (priv->pos = msg->len && !(priv->flags & ID_LAST_MSG))
 		rcar_i2c_next_msg(priv);
@@ -436,7 +424,11 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
 static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 {
 	struct rcar_i2c_priv *priv = ptr;
-	u32 msr;
+	u32 msr, val;
+
+	/* Clear START or STOP as soon as we can */
+	val = rcar_i2c_read(priv, ICMCR);
+	rcar_i2c_write(priv, ICMCR, val & RCAR_BUS_MASK_DATA);
 
 	msr = rcar_i2c_read(priv, ICMSR);
 
@@ -458,7 +450,6 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 	/* Nack */
 	if (msr & MNR) {
 		/* HW automatically sends STOP after received NACK */
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 		rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
 		rcar_i2c_flags_set(priv, ID_NACK);
 		goto out;
-- 
2.1.4


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH v2 09/10] i2c: rcar: revoke START request early
@ 2015-11-12 14:42   ` Wolfram Sang
  0 siblings, 0 replies; 6+ messages in thread
From: Wolfram Sang @ 2015-11-12 14:42 UTC (permalink / raw)
  To: linux-i2c
  Cc: linux-sh, Magnus Damm, Simon Horman, Laurent Pinchart,
	Geert Uytterhoeven, Wolfram Sang, Yoshihiro Shimoda,
	Kuninori Morimoto

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

If we don't clear START generation as soon as possible, it may cause
another message to be generated, e.g. when receiving NACK in address
phase. To keep the race window as small as possible, we clear it right
at the beginning of the interrupt. We don't need any checks since we
always want to stop START and STOP generation on the next occasion after
we started it.

This patch improves the situation but sadly does not completely fix it.
It is still to be researched if we can do better given this HW design.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 drivers/i2c/busses/i2c-rcar.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index 8ad4c7d1ad8654..64a01c0177463a 100644
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -83,6 +83,7 @@
 
 #define RCAR_BUS_PHASE_START	(MDBS | MIE | ESG)
 #define RCAR_BUS_PHASE_DATA	(MDBS | MIE)
+#define RCAR_BUS_MASK_DATA	(~(ESG | FSB) & 0xFF)
 #define RCAR_BUS_PHASE_STOP	(MDBS | MIE | FSB)
 
 #define RCAR_IRQ_SEND	(MNR | MAL | MST | MAT | MDE)
@@ -289,13 +290,6 @@ static int rcar_i2c_irq_send(struct rcar_i2c_priv *priv, u32 msr)
 	if (!(msr & MDE))
 		return 0;
 
-	/*
-	 * If address transfer phase finished,
-	 * goto data phase.
-	 */
-	if (msr & MAT)
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
-
 	if (priv->pos < msg->len) {
 		/*
 		 * Prepare next data to ICRXTX register.
@@ -347,11 +341,7 @@ static int rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
 		return 0;
 
 	if (msr & MAT) {
-		/*
-		 * Address transfer phase finished,
-		 * but, there is no data at this point.
-		 * Do nothing.
-		 */
+		/* Address transfer phase finished, but no data at this point. */
 	} else if (priv->pos < msg->len) {
 		/*
 		 * get received data
@@ -367,8 +357,6 @@ static int rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr)
 	 */
 	if (priv->pos + 1 >= msg->len)
 		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_STOP);
-	else
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 
 	if (priv->pos == msg->len && !(priv->flags & ID_LAST_MSG))
 		rcar_i2c_next_msg(priv);
@@ -436,7 +424,11 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv)
 static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 {
 	struct rcar_i2c_priv *priv = ptr;
-	u32 msr;
+	u32 msr, val;
+
+	/* Clear START or STOP as soon as we can */
+	val = rcar_i2c_read(priv, ICMCR);
+	rcar_i2c_write(priv, ICMCR, val & RCAR_BUS_MASK_DATA);
 
 	msr = rcar_i2c_read(priv, ICMSR);
 
@@ -458,7 +450,6 @@ static irqreturn_t rcar_i2c_irq(int irq, void *ptr)
 	/* Nack */
 	if (msr & MNR) {
 		/* HW automatically sends STOP after received NACK */
-		rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA);
 		rcar_i2c_write(priv, ICMIER, RCAR_IRQ_STOP);
 		rcar_i2c_flags_set(priv, ID_NACK);
 		goto out;
-- 
2.1.4

^ permalink raw reply related	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2015-11-12 14:43 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-11-12 14:42 [PATCH v2 07/10] i2c: rcar: don't issue stop when HW does it automatically Wolfram Sang
2015-11-12 14:42 ` Wolfram Sang
2015-11-12 14:42 ` [PATCH v2 08/10] i2c: rcar: check master irqs before slave irqs Wolfram Sang
2015-11-12 14:42   ` Wolfram Sang
2015-11-12 14:42 ` [PATCH v2 09/10] i2c: rcar: revoke START request early Wolfram Sang
2015-11-12 14:42   ` Wolfram Sang

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.