Re: [PATCH 1/1] I2C: designware: fix IO timeout issue for AMD controller

Mika Westerberg
2015-11-05T13:55:34Z

On Thu, Nov 05, 2015 at 08:34:44PM +0800, Xiangliang Yu wrote:
> Because of some hardware limitation, AMD I2C controller can't
> trigger next interrupt if interrupt status has been changed
> after clearing interrupt status bits. Then, I2C will lost
> interrupt and IO timeout.
>
> According to hardware design, this patch implements a workaround
> to disable i2c controller interrupt after clearing interrupt bits
> when entering ISR and to enable i2c interrupt before exiting ISR.
>
> To reduce the performance impacts on other vendors, use unlikely
> function to check flag in ISR.
>
> Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
> ---
> drivers/i2c/busses/i2c-designware-core.c | 6 ++++++
> drivers/i2c/busses/i2c-designware-core.h | 1 +
> drivers/i2c/busses/i2c-designware-platdrv.c | 4 ++++
> 3 files changed, 11 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
> index 7441cdc..04e7b65 100644
> --- a/drivers/i2c/busses/i2c-designware-core.c
> +++ b/drivers/i2c/busses/i2c-designware-core.c
> @@ -783,6 +783,9 @@ irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
>
> stat = i2c_dw_read_clear_intrbits(dev);

What if the status changes right here, before you go and mask the
interrupt?

>
> + if (unlikely(dev->accessor_flags & ACCESS_INTR_MASK))
> + i2c_dw_disable_int(dev);
> +
> if (stat & DW_IC_INTR_TX_ABRT) {
> dev->cmd_err |= DW_IC_ERR_TX_ABRT;
> dev->status = STATUS_IDLE;
> @@ -811,6 +814,9 @@ tx_aborted:
> if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
> complete(&dev->cmd_complete);
>
> + if (unlikely(dev->accessor_flags & ACCESS_INTR_MASK))
> + dw_writel(dev, DW_IC_INTR_DEFAULT_MASK, DW_IC_INTR_MASK);

The driver disables TX interrupt when it is not needed anymore or when
TX gets aborted but the above will re-enable all interrupts regardless.
Is that the intention?

> +
> return IRQ_HANDLED;
> }
> EXPORT_SYMBOL_GPL(i2c_dw_isr);
> diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
> index 9630222..808ef6a 100644
> --- a/drivers/i2c/busses/i2c-designware-core.h
> +++ b/drivers/i2c/busses/i2c-designware-core.h
> @@ -111,6 +111,7 @@ struct dw_i2c_dev {
>
> #define ACCESS_SWAP 0x00000001
> #define ACCESS_16BIT 0x00000002
> +#define ACCESS_INTR_MASK 0x00000004
>
> extern u32 dw_readl(struct dw_i2c_dev *dev, int offset);
> extern void dw_writel(struct dw_i2c_dev *dev, u32 b, int offset);
> diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> index 472b882..0c59357 100644
> --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> @@ -251,6 +251,10 @@ static int dw_i2c_probe(struct platform_device *pdev)
> dev->rx_fifo_depth = ((param1 >> 8) & 0xff) + 1;
> dev->adapter.nr = pdev->id;
> }
> +
> + if (!strncmp(pdev->name, "AMD0010", 7))
> + dev->accessor_flags |= ACCESS_INTR_MASK;
> +

Can't you put this to ->driver_data? For example it could refer to a
configuration structure that then contains quirk flags.

> r = i2c_dw_init(dev);
> if (r)
> return r;
> --
> 1.9.1