On 1/19/23 10:51, Charles Keepax wrote:
> Currently the SoundWire core will loop handling slave alerts but it will
> only handle those present when the alert was first raised. This causes
> some issues with the Cadence SoundWire IP, which only generates an IRQ
> when alert changes state. This means that if a new alert arrives whilst
> old alerts are being handled it will not be handled in the currently
> loop and then no further alerts will be processed since alert never
> changes state to trigger a new IRQ.
>
> Correct this issue by allowing the core to handle all pending alerts in
> the IRQ handling loop. The code will still only loop up to
> SDW_READ_INTR_CLEAR_RETRY times, so it shouldn't be possible for it get
> completely stuck and if you are generating IRQs faster than you can
> handle them you likely have bigger problems anyway.
The change makes sense, but it's a bit odd to change the way the
interrupts are handled because of a specific design. The bus should be
able to deal with various designs, not force a one-size-fits-all policy
that may not be quite right in all cases.
Could we have a new flag at the bus level that says that peripheral
interrupts are not filtered, and set if for the Intel case?
We could similarly make the SDW_READ_INTR_CLEAR_RETRY constant
bus/platform specific. The SoundWire spec mandates that we re-read the
status after clearing the interrupt, but it doesn't say how to deal with
recurring interrupts.
> Signed-off-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
> ---
> drivers/soundwire/bus.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> index 633d411b64f35..daee2cca94a4d 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -1560,7 +1560,7 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
> unsigned long port;
> bool slave_notify;
> u8 sdca_cascade = 0;
> - u8 buf, buf2[2], _buf, _buf2[2];
> + u8 buf, buf2[2];
> bool parity_check;
> bool parity_quirk;
>
> @@ -1716,9 +1716,9 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
> "SDW_SCP_INT1 recheck read failed:%d\n", ret);
> goto io_err;
> }
> - _buf = ret;
> + buf = ret;
>
> - ret = sdw_nread_no_pm(slave, SDW_SCP_INTSTAT2, 2, _buf2);
> + ret = sdw_nread_no_pm(slave, SDW_SCP_INTSTAT2, 2, buf2);
> if (ret < 0) {
> dev_err(&slave->dev,
> "SDW_SCP_INT2/3 recheck read failed:%d\n", ret);
> @@ -1736,12 +1736,8 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
> }
>
> /*
> - * Make sure no interrupts are pending, but filter to limit loop
> - * to interrupts identified in the first status read
> + * Make sure no interrupts are pending
> */
> - buf &= _buf;
> - buf2[0] &= _buf2[0];
> - buf2[1] &= _buf2[1];
> stat = buf || buf2[0] || buf2[1] || sdca_cascade;
>
> /*
