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.
@@ -1681,6 +1681,9 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) struct device *dev = &slave->dev; struct sdw_driver *drv = drv_to_sdw_driver(dev->driver);
+ if (drv->ops && drv->ops->interrupt_callback_early) + drv->ops->interrupt_callback_early(slave); + if (drv->ops && drv->ops->interrupt_callback) { slave_intr.sdca_cascade = sdca_cascade; slave_intr.control_port = clear;
Would that similarly worry you? As in is it the client driver writer dealing with 2 points of entry that worries you, or something deeper relating to the IRQs?
Also if it helps I could go over in a little more detail how the IRQs on our device works and why that means I would prefer to have the option to use both. There are alternatives but they arn't really as pretty.
Thanks, Charles