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SubjectRe: [PATCH] i2c: aspeed: Acknowledge most interrupts early in interrupt handler
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On 9/13/2018 8:30 PM, Guenter Roeck wrote:
> Commit 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events
> properly") moved interrupt acknowledgment to the end of the interrupt
> handler. In part this was done because the AST2500 datasheet says:
>
> I2CD10 Interrupt Status Register
> bit 2 Receive Done Interrupt status
> S/W needs to clear this status bit to allow next data receiving.
>
> Acknowledging Receive Done before receive data was handled resulted in
> receive errors on high speed I2C busses.
>
> However, interrupt acknowledgment was not only moved to the end of the
> interrupt handler for Receive Done Interrupt status, but for all interrupt
> status bits. This could result in race conditions if a second interrupt was
> received during interrupt handling and not handled but still acknowledged
> at the end of the interrupt handler.
>
> Acknowledge only "Receive Done Interrupt status" late in the interrupt
> handler to solve the problem.
>
> Fixes: 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events properly")
> Cc: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> Cc: Joel Stanley <joel@jms.id.au>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> drivers/i2c/busses/i2c-aspeed.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index c258c4d9a4c0..3d518e09369f 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -552,6 +552,9 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
>
> spin_lock(&bus->lock);
> irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
> + /* Ack all interrupts except for Rx done */
> + writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE,
> + bus->base + ASPEED_I2C_INTR_STS_REG);
> irq_remaining = irq_received;
>
> #if IS_ENABLED(CONFIG_I2C_SLAVE)
> @@ -584,8 +587,10 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
> "irq handled != irq. expected 0x%08x, but was 0x%08x\n",
> irq_received, irq_handled);
>
> - /* Ack all interrupt bits. */
> - writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
> + /* Ack Rx done */
> + if (irq_received & ASPEED_I2CD_INTR_RX_DONE)
> + writel(ASPEED_I2CD_INTR_RX_DONE,
> + bus->base + ASPEED_I2C_INTR_STS_REG);
> spin_unlock(&bus->lock);
> return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
> }
>

Looks good to me. Thanks! :)

Acked-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>

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