diff options
| author | Wolfram Sang <wsa+renesas@sang-engineering.com> | 2020-12-23 18:21:51 +0100 |
|---|---|---|
| committer | Wolfram Sang <wsa@kernel.org> | 2021-01-05 16:29:06 +0100 |
| commit | c7b514ec979e23a08c411f3d8ed39c7922751422 (patch) | |
| tree | 26283d7292331bc63232f611677bf13d7123f951 /drivers/i2c | |
| parent | 357ee8841d0b7bd822f25fc768afbc0c2ab7e47b (diff) | |
| download | linux-c7b514ec979e23a08c411f3d8ed39c7922751422.tar.bz2 | |
i2c: rcar: faster irq code to minimize HW race condition
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 <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/busses/i2c-rcar.c | 11 |
1 files changed, 4 insertions, 7 deletions
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); |