Hello Greg,
Wolfram recommends the backporting of this series in order to improve the situation with a race condition. Do you think you can take this series for 4.4 stable?
This series applies on 4.4.133, and depends on series: "Fix R-Car I2C data byte sent twice issue"
Thanks, Fab
Wolfram Sang (3): i2c: rcar: don't issue stop when HW does it automatically i2c: rcar: check master irqs before slave irqs i2c: rcar: revoke START request early
drivers/i2c/busses/i2c-rcar.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-)
From: Wolfram Sang wsa+renesas@sang-engineering.com
commit d89667b14f9d13b684287f6189ca209af5feee43 upstream.
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 Signed-off-by: Wolfram Sang wsa@the-dreams.de [fabrizio: cherry-pick to 4.4] Signed-off-by: Fabrizio Castro fabrizio.castro@bp.renesas.com Reviewed-by: Biju Das biju.das@bp.renesas.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 44662e2..6f23b97 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -455,8 +455,8 @@ 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;
From: Wolfram Sang wsa+renesas@sang-engineering.com
commit c3be0af15959e11fa535d5332ab3d7cf34abd09b upstream.
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 Signed-off-by: Wolfram Sang wsa@the-dreams.de [fabrizio: cherry-pick to 4.4] Signed-off-by: Fabrizio Castro fabrizio.castro@bp.renesas.com Reviewed-by: Biju Das biju.das@bp.renesas.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 6f23b97..ee3e02a 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -432,19 +432,17 @@ 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 */ @@ -481,8 +479,7 @@ out: wake_up(&priv->wait); }
-exit: - return result; + return IRQ_HANDLED; }
static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
From: Wolfram Sang wsa+renesas@sang-engineering.com
commit 52df445f29b79006d8b2dcd129152987c0d3bd64 upstream.
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 Signed-off-by: Wolfram Sang wsa@the-dreams.de [fabrizio: cherry-pick to 4.4] Signed-off-by: Fabrizio Castro fabrizio.castro@bp.renesas.com Reviewed-by: Biju Das biju.das@bp.renesas.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 ee3e02a..6f89484 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 void rcar_i2c_irq_send(struct rcar_i2c_priv *priv, u32 msr) if (!(msr & MDE)) return;
- /* - * 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. @@ -345,11 +339,7 @@ static void rcar_i2c_irq_recv(struct rcar_i2c_priv *priv, u32 msr) return;
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 @@ -365,8 +355,6 @@ static void 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); @@ -432,7 +420,11 @@ 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);
@@ -454,7 +446,6 @@ 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;
On Wed, May 30, 2018 at 11:07:10AM +0100, Fabrizio Castro wrote:
Hello Greg,
Wolfram recommends the backporting of this series in order to improve the situation with a race condition. Do you think you can take this series for 4.4 stable?
This series applies on 4.4.133, and depends on series: "Fix R-Car I2C data byte sent twice issue"
All now queued up, thanks.
greg k-h
linux-stable-mirror@lists.linaro.org
-
Fabrizio Castro -
Greg Kroah-Hartman