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SubjectRe: [PATCH] i2c: designware: call i2c_dw_read_clear_intrbits_slave() once
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Hi

On 10/20/20 11:33 AM, Michael Wu wrote:
> i2c_dw_read_clear_intrbits_slave() was called per each interrupt handle.
> It caused some interrupt bits which haven't been handled yet were cleared,
> the corresponding handlers would do nothing due to interrupt bits been
> discarded. For example,
>
> $ i2cset -f -y 2 0x42 0x00 0x41; dmesg -c
> [0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
> [1][irq_handler ]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
> WRITE_RECEIVED
> [0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
> [1][irq_handler ]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
> WRITE_RECEIVED
>
> t1: ISR with the 1st IC_INTR_RX_FULL.
> t2: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave().
> t3: Enter i2c_dw_irq_handler_slave() and then do
> i2c_slave_event(WRITE_RECEIVED) because
> if (stat & DW_IC_INTR_RX_FULL).
> t4: ISR with both IC_INTR_STOP_DET and the 2nd IC_INTR_RX_FULL.
> t5: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave(). The
> current IC_INTR_STOP_DET is cleared by this
> i2c_dw_read_clear_intrbits_slave().
> t6: Enter i2c_dw_irq_handler_slave() and then do
> i2c_slave_event(WRITE_RECEIVED) because
> if (stat & DW_IC_INTR_RX_FULL).
> t7: i2c_slave_event(STOP) never be done because IC_INTR_STOP_DET was
> cleared in t5.
>
> The root cause is that i2c_dw_read_clear_intrbits_slave() was called many
> times. Calling i2c_dw_read_clear_intrbits_slave() once in one ISR and take
> the returned stat for later handling is the solution.
>
> Signed-off-by: Michael Wu <michael.wu@vatics.com>
> ---
> drivers/i2c/busses/i2c-designware-slave.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-designware-slave.c b/drivers/i2c/busses/i2c-designware-slave.c
> index 44974b53a626..02e7c5171827 100644
> --- a/drivers/i2c/busses/i2c-designware-slave.c
> +++ b/drivers/i2c/busses/i2c-designware-slave.c
> @@ -159,7 +159,6 @@ static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
> u32 raw_stat, stat, enabled, tmp;
> u8 val = 0, slave_activity;
>
> - regmap_read(dev->map, DW_IC_INTR_STAT, &stat);
> regmap_read(dev->map, DW_IC_ENABLE, &enabled);
> regmap_read(dev->map, DW_IC_RAW_INTR_STAT, &raw_stat);
> regmap_read(dev->map, DW_IC_STATUS, &tmp);
> @@ -168,13 +167,11 @@ static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
> if (!enabled || !(raw_stat & ~DW_IC_INTR_ACTIVITY) || !dev->slave)
> return 0;
>
> + stat = i2c_dw_read_clear_intrbits_slave(dev);
> dev_dbg(dev->dev,
> "%#x STATUS SLAVE_ACTIVITY=%#x : RAW_INTR_STAT=%#x : INTR_STAT=%#x\n",
> enabled, slave_activity, raw_stat, stat);
>
> - if ((stat & DW_IC_INTR_RX_FULL) && (stat & DW_IC_INTR_STOP_DET))
> - i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED, &val);
> -

...

> +
> + if ((stat & DW_IC_INTR_RX_FULL) && (stat & DW_IC_INTR_STOP_DET))
> + i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED, &val);

Was this move a leftover that got committed by accident? I think it's
better to have this logic change in another patch. Or was it even
questionable to move the I2C_SLAVE_WRITE_REQUESTED reporting after all
other?

Jarkko

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