On 1/20/23 04:14, Charles Keepax wrote: > On Thu, Jan 19, 2023 at 11:27:14AM -0600, Pierre-Louis Bossart wrote: >> 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. > > Perhaps I should have phrased the commit message differently > here. To be honest I am not really convince the old code makes > a huge amount of sense. So I would prefer not to add a flag > enabling the weird behaviour. > > I would be of the opinion that there are really two options > for IRQ handling code like this that make sense: > > 1) Loop until the IRQs are handled, ie. it is the soundwire > core's responsibility to make sure all the IRQs are handled > before moving on. > > 2) Just handle the IRQs available when the function is called, > ie. it is the drivers responsibility to keep calling the core > until the IRQs are handled. > > That way there is a clearly defined who that is responsible. > The old code is a weird mix of the two where most of the time > it is the soundwire core's responsibly to handle recurring > IRQs unless a new one happens in which case it is the drivers > responsibilty to recall the core. > > Also the new code will still work for drivers that have level > IRQs and recall the core, without any modification of those > drivers. So I don't see what anyone would be gaining from the > old system. I think the intent of the 'old code' was the option 2), expect that it's broken on Intel platforms and not possible because of the hardware design. I am good with your two suggested options. > Regarding making the clear retries platform specific that makes > sense to me but is clearly a separate patch. I will add it onto > my soundwire todo list. yes, it's a separate patch indeed.
