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@xxxxxxxxxxxxxxx> 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 >>>> problems. >>>> >>> >>> 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 >> accurate. >> >> 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@xxxxxxxx> Thanks, C. > Guenter > > --- > > 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) > > spin_lock(&bus->lock); > 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); > spin_unlock(&bus->lock); > return irq_remaining ? IRQ_NONE : IRQ_HANDLED; > } >
