From: Wolfram Sang <wsa@the-dreams.de> To: linux-i2c@vger.kernel.org Cc: linux-sh@vger.kernel.org, Magnus Damm <magnus.damm@gmail.com>, Simon Horman <horms@verge.net.au>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Wolfram Sang <wsa@the-dreams.de>, Kuninori Morimoto <kuninori.morimoto.gx@gmail.com>, Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> Subject: [PATCH v3 09/11] i2c: rcar: revoke START request early Date: Thu, 19 Nov 2015 15:56:49 +0000 [thread overview] Message-ID: <1447948611-2615-10-git-send-email-wsa@the-dreams.de> (raw) In-Reply-To: <1447948611-2615-1-git-send-email-wsa@the-dreams.de> 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 f237b4fc5b5e55..40979130200935 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; -- 2.1.4
WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa@the-dreams.de> To: linux-i2c@vger.kernel.org Cc: linux-sh@vger.kernel.org, Magnus Damm <magnus.damm@gmail.com>, Simon Horman <horms@verge.net.au>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Wolfram Sang <wsa@the-dreams.de>, Kuninori Morimoto <kuninori.morimoto.gx@gmail.com>, Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> Subject: [PATCH v3 09/11] i2c: rcar: revoke START request early Date: Thu, 19 Nov 2015 16:56:49 +0100 [thread overview] Message-ID: <1447948611-2615-10-git-send-email-wsa@the-dreams.de> (raw) In-Reply-To: <1447948611-2615-1-git-send-email-wsa@the-dreams.de> 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 f237b4fc5b5e55..40979130200935 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; -- 2.1.4
next prev parent reply other threads:[~2015-11-19 15:56 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-11-19 15:56 [PATCH v3 00/11] i2c: rcar: tackle race conditions in the driver Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 01/11] i2c: rcar: make sure clocks are on when doing clock calculation Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 02/11] i2c: rcar: rework hw init Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 03/11] i2c: rcar: remove unused IOERROR state Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 04/11] i2c: rcar: remove spinlock Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 05/11] i2c: rcar: refactor setup of a msg Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 06/11] i2c: rcar: init new messages in irq Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 07/11] i2c: rcar: don't issue stop when HW does it automatically Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 08/11] i2c: rcar: check master irqs before slave irqs Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang [this message] 2015-11-19 15:56 ` [PATCH v3 09/11] i2c: rcar: revoke START request early Wolfram Sang 2016-03-31 21:02 ` Sergei Shtylyov 2016-03-31 21:02 ` Sergei Shtylyov 2016-03-31 22:48 ` Wolfram Sang 2016-03-31 22:48 ` Wolfram Sang 2016-04-01 19:55 ` Sergei Shtylyov 2016-04-01 19:55 ` Sergei Shtylyov 2016-04-01 20:14 ` Wolfram Sang 2016-04-01 20:14 ` Wolfram Sang 2016-04-01 23:05 ` Sergei Shtylyov 2016-04-01 23:05 ` Sergei Shtylyov 2016-04-02 7:27 ` Wolfram Sang 2016-04-02 7:27 ` Wolfram Sang 2016-04-02 12:51 ` Sergei Shtylyov 2016-04-02 12:51 ` Sergei Shtylyov 2016-04-03 8:25 ` Wolfram Sang 2016-04-03 8:25 ` Wolfram Sang 2016-04-03 13:35 ` Sergei Shtylyov 2016-04-03 13:35 ` Sergei Shtylyov 2016-04-03 13:47 ` Wolfram Sang 2016-04-03 13:47 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 10/11] i2c: rcar: clean up after refactoring Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 15:56 ` [PATCH v3 11/11] i2c: rcar: handle difference in setting up non-first message Wolfram Sang 2015-11-19 15:56 ` Wolfram Sang 2015-11-19 16:01 ` [PATCH v3 00/11] i2c: rcar: tackle race conditions in the driver Laurent Pinchart 2015-11-19 16:01 ` Laurent Pinchart 2015-11-30 13:27 ` Wolfram Sang 2015-11-30 13:27 ` Wolfram Sang
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