From c7b514ec979e23a08c411f3d8ed39c7922751422 Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Wed, 23 Dec 2020 18:21:51 +0100 Subject: i2c: rcar: faster irq code to minimize HW race condition MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To avoid the HW race condition on R-Car Gen2 and earlier, we need to write to ICMCR as soon as possible in the interrupt handler. We can improve this by writing a static value instead of masking out bits. Signed-off-by: Wolfram Sang Reviewed-by: Niklas Söderlund Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-rcar.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c index 217def2d7cb4..824586d7ee56 100644 --- a/drivers/i2c/busses/i2c-rcar.c +++ b/drivers/i2c/busses/i2c-rcar.c @@ -91,7 +91,6 @@ #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) @@ -621,7 +620,7 @@ static bool rcar_i2c_slave_irq(struct rcar_i2c_priv *priv) /* * This driver has a lock-free design because there are IP cores (at least * R-Car Gen2) which have an inherent race condition in their hardware design. - * There, we need to clear RCAR_BUS_MASK_DATA bits as soon as possible after + * There, we need to switch to RCAR_BUS_PHASE_DATA as soon as possible after * the interrupt was generated, otherwise an unwanted repeated message gets * generated. It turned out that taking a spinlock at the beginning of the ISR * was already causing repeated messages. Thus, this driver was converted to @@ -630,13 +629,11 @@ 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, val; + u32 msr; /* Clear START or STOP immediately, except for REPSTART after read */ - if (likely(!(priv->flags & ID_P_REP_AFTER_RD))) { - val = rcar_i2c_read(priv, ICMCR); - rcar_i2c_write(priv, ICMCR, val & RCAR_BUS_MASK_DATA); - } + if (likely(!(priv->flags & ID_P_REP_AFTER_RD))) + rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_DATA); msr = rcar_i2c_read(priv, ICMSR); -- cgit v1.2.3