On 1/23/23 08:53, Charles Keepax wrote: > On Fri, Jan 20, 2023 at 10:20:50AM -0600, Pierre-Louis Bossart wrote: >> On 1/20/23 03:59, Charles Keepax wrote: >>> On Thu, Jan 19, 2023 at 11:12:04AM -0600, Pierre-Louis Bossart wrote: >>>> There should be an explanation and something checking that both are not >>>> used concurrently. >>> >>> I will try to expand the explanation a litte, but I dont see any >>> reason to block calling both handlers, no ill effects would come >>> for a driver having both and it is useful if any soundwire >>> specific steps are needed that arn't on other control buses. >> >> I think it's problematic if the peripheral tries to wake-up the manager >> from clock-stop with both an in-band wake (i.e. drive the data line >> high) and a separate GPIO-based interrupt. It's asking for trouble IMHO. >> We spent hours in the MIPI team to make sure there were no races between >> the manager-initiated restarts and peripheral-initiated restarts, adding >> a 3rd mechanism in the mix gives me a migraine already. > > Apologies but I am struggling see why this has any bearing on > the case of a device that does both an in-band and out-of-band > wake. The code we are adding in this patch will only be called in the > in-band case. handle_nested_irq doesn't do any hardware magic or > schedule any threads, it just calls a function that was provided > when the client called request_threaded_irq. The only guarantee > of atomicity you have on the interrupt_callback is sdw_dev_lock > and that is being held across both calls after the patch. > > Could you be a little more specific on what you mean by this > represents a 3rd mechanism, to me this isn't a new mechanism just > an extra callback? Say for example this patch added an > interrupt_callback_early to sdw_slave_ops that is called just > before interrupt_callback. Well, the main concern is exiting the clock-stop. That is handled by the manager and could be done a) as the result of the framework deciding that something needs to be done (typically as a result of user/applications starting a stream) b) by the device with an in-band wake in case of e.g. jack detection or acoustic events detected c) same as b) but with a separate out-of-band interrupt. I'd like to make sure b) and c) are mutually-exclusive options, and that the device will not throw BOTH an in-band wake and an external interrupt.
