-----Original Message----- From: Wolfram Sang [mailto:wsa@xxxxxxxxxxxxx] Sent: Wednesday, April 29, 2020 3:54 PM To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx> Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx>; Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>; Joel Stanley <joel@xxxxxxxxx>; Andrew Jeffery <andrew@xxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx; openbmc@xxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-aspeed@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx Subject: Re: [PATCH v0 linux master] i2c/busses: Avoid i2c interrupt status clear race condition. On Wed, Apr 29, 2020 at 11:37:37AM +0800, ryan_chen wrote: > In AST2600 there have a slow peripheral bus between CPU and i2c > controller. > Therefore GIC i2c interrupt status clear have delay timing, when CPU > issue write clear i2c controller interrupt status. > To avoid this issue, the driver need have read after write clear at > i2c ISR. > > Signed-off-by: ryan_chen <ryan_chen@xxxxxxxxxxxxxx> v0? is it a prototype? [Ryan Chen] It is not prototype it is official patch. And is there maybe a Fixes: tag for it? [Ryan Chen] Yes it is a fix patch. > --- > drivers/i2c/busses/i2c-aspeed.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/i2c/busses/i2c-aspeed.c > b/drivers/i2c/busses/i2c-aspeed.c index 07c1993274c5..f51702d86a90 > 100644 > --- a/drivers/i2c/busses/i2c-aspeed.c > +++ b/drivers/i2c/busses/i2c-aspeed.c > @@ -603,6 +603,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id) > /* Ack all interrupts except for Rx done */ > writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE, > bus->base + ASPEED_I2C_INTR_STS_REG); > + readl(bus->base + ASPEED_I2C_INTR_STS_REG); > irq_remaining = irq_received; > > #if IS_ENABLED(CONFIG_I2C_SLAVE) > @@ -645,9 +646,11 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id) > irq_received, irq_handled); > > /* Ack Rx done */ > - if (irq_received & ASPEED_I2CD_INTR_RX_DONE) > + if (irq_received & ASPEED_I2CD_INTR_RX_DONE) { > writel(ASPEED_I2CD_INTR_RX_DONE, > bus->base + ASPEED_I2C_INTR_STS_REG); > + readl(bus->base + ASPEED_I2C_INTR_STS_REG); > + } > spin_unlock(&bus->lock); > return irq_remaining ? IRQ_NONE : IRQ_HANDLED; } > -- > 2.17.1 >
