[PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly
Cédric Le Goater
clg at kaod.org
Wed Sep 12 15:57:24 AEST 2018
On 09/12/2018 01:33 AM, Guenter Roeck wrote:
> On Wed, Sep 12, 2018 at 08:23:29AM +0930, Joel Stanley wrote:
>> On Wed, 12 Sep 2018 at 07:48, Jae Hyun Yoo <jae.hyun.yoo at linux.intel.com> wrote:
>>> On 9/11/2018 1:41 PM, Guenter Roeck wrote:
>>>> On Tue, Sep 11, 2018 at 01:30:41PM -0700, Jae Hyun Yoo wrote:
>>>>> I checked this patch again but it doesn't have any change that could
>>>>> affect to the probing flow. I'll debug the issue on qemu 3.0 environment
>>>>> and will share if I find something.
>>>> The problem may be that qemu and the new code disagree how interrupts
>>>> should be generated and handled, and the new code does not handle the
>>>> interrupts it receives from the simulated hardware. This will result
>>>> in i2c device probe failure, which in turn can cause all kinds of
>>> Yes, that makes sense. Looks like it should be reverted until the issue
>>> is fixed. Will submit a patch to revert it.
>> Let's not rush. The qemu model was written in order to allow us to
>> test the kernel code, and was validated by the kernel driver we have.
>> We've had situations in the past (with the i2c driver in fact) where a
>> change in the driver required an update of the model to be more
>> I suggest we wait until Cedric has a chance to look at the issue
>> before reverting the patch.
> Looking into the patch, clearing the interrupt status at the end of an
> interrupt handler is always suspicious and tends to result in race
yes. That happened in the past with the I2C aspeed driver. I can not find
the thread anymore but we had to move up the ack of the interrupts.
QEMU tends to be much faster to fire interrupts than real HW.
> conditions (because additional interrupts may have arrived while handling
> the existing interrupts, or because interrupt handling itself may trigger
> another interrupt). With that in mind, the following patch fixes the
> problem for me.
Acked-by: Cédric Le Goater <clg at kaod.org>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index c258c4d9a4c0..c488e6950b7c 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -552,6 +552,8 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
> irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
> + /* Ack all interrupt bits. */
> + writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
> irq_remaining = irq_received;
> #if IS_ENABLED(CONFIG_I2C_SLAVE)
> @@ -584,8 +586,6 @@ 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);
> return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
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