Messages in this thread | | | Date | Mon, 23 Jan 2023 16:08:02 +0000 | Subject | Re: [PATCH 2/2] soundwire: bus: Allow SoundWire peripherals to register IRQ handlers | From | Richard Fitzgerald <> |
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On 23/01/2023 15:50, Pierre-Louis Bossart wrote: > > > 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.
Why would it be a problem if the device did (b) and (c)? (c) is completely invisible to the SoundWire core and not something that it has to handle. The handler for an out-of-band interrupt must call pm_runtime_get_sync() or pm_runtime_resume_and_get() and that would wake its own driver and the host controller.
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