On 4/18/23 09:06, Charles Keepax wrote:
> It makes sense to have only a single point responsible for ensuring
> that all currently pending IRQs are handled. The current code in
> sdw_handle_slave_alerts confusingly splits this process in two. This
> code will loop until the asserted IRQs are cleared but it will only
> handle IRQs that were already asserted when it was called. This
> means the caller must also loop (either manually, or through its IRQ
> mechanism) until the IRQs are all handled. It makes sense to either do
> all the looping in sdw_handle_slave_alerts or do no looping there and
> let the host controller repeatedly call it until things are handled.
>
> There are realistically two sensible host controllers, those that
> will generate an IRQ when the alert status changes and those
> that will generate an IRQ continuously whilst the alert status
> is high. The current code will work fine for the second of those
> systems but not the first with out additional looping in the host
> controller. Removing the code that filters out new IRQs whilst
> the handler is running enables both types of host controller to be
> supported and simplifies the code. The code will still only loop up to
> SDW_READ_INTR_CLEAR_RETRY times, so it shouldn't be possible for it to
> get completely stuck handling IRQs forever, and if you are generating
> IRQs faster than you can handle them you likely have bigger problems
> anyway.
>
> This fixes an issue on the Cadence SoundWire IP, which only generates
> IRQs on an alert status change, where an alert which arrives whilst
> another alert is being handled will never be handled and will block
> all future alerts from being handled.
>
> Signed-off-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>
Makes sense to me, thanks for the patch.
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
>
> Changes since v1:
> - Update commit message
>
> Thanks,
> Charles
>
> 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 1ea6a64f8c4a5..338f4f0b5d0cc 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -1588,7 +1588,7 @@ 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;
>
> @@ -1745,9 +1745,9 @@ 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);
> @@ -1765,12 +1765,8 @@ 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;
>
> /*
