Le lun. 6 janv. 2025 à 16:29, David Lechner <dlechner@xxxxxxxxxxxx> a écrit : > > On 12/28/24 8:24 AM, Jonathan Cameron wrote: > > On Tue, 24 Dec 2024 10:34:32 +0100 > > Julien Stephan <jstephan@xxxxxxxxxxxx> wrote: > > > >> The alert functionality is an out of range indicator and can be used as an > >> early indicator of an out of bounds conversion result. > >> > >> ALERT_LOW_THRESHOLD and ALERT_HIGH_THRESHOLD registers are common to all > >> channels. > >> > >> When using 1 SDO line (only mode supported by the driver right now), i.e > >> data outputs only on SDOA, SDOB (or SDOD for 4 channels variants) is > >> used as an alert pin. The alert pin is updated at the end of the > >> conversion (set to low if an alert occurs) and is cleared on a falling > >> edge of CS. > >> > >> The ALERT register contains information about the exact alert status: > >> channel and direction. Unfortunately we can't read this register because > >> in buffered read we cannot claim for direct mode. > >> > >> User can set high/low thresholds and enable event detection using the > >> regular iio events: > >> > >> events/in_thresh_falling_value > >> events/in_thresh_rising_value > >> events/thresh_either_en > >> > >> If the interrupt properties is present in the device tree, an IIO event > >> will be generated for each interrupt received. > >> Because we cannot read ALERT register, we can't determine the exact > >> channel that triggers the alert, neither the direction (hight/low > >> threshold violation), so we send and IIO_EV_DIR_EITHER event for all > >> channels. > >> > >> In buffered reads, if input stays out of thresholds limit, an interrupt > >> will be generated for each sample read, because the alert pin is cleared > >> on a falling edge of CS (i.e when starting a new conversion). To avoid > >> generating to much interrupt, we introduce a reset_timeout that can be > >> used to disable interrupt for a given time (in ms) > >> > >> events/thresh_either_reset_timeout > >> > >> When an interrupt is received, interrupts are disabled and re-enabled > >> after thresh_either_reset_timeout ms. If the reset timeout is set to 0, > >> interrupt are re-enabled directly. > >> Note: interrupts are always disabled at least during the handling of the > >> previous interrupt, because each read triggers 2 transactions, that can > >> lead to 2 interrupts for a single user read. IRQF_ONESHOT is not enough, > >> because, it postpones the 2nd irq after the handling of the first one, > >> which can still trigger 2 interrupts for a single user read. > > > > After some of our recent discussions around interrupt handling and > > the guarantees (that aren't) made, even disabling the interrupt doesn't > > prevent some irq chips queuing up future interrupts. > > > > https://lore.kernel.org/all/io53lznz3qp3jd5rohqsjhosnmdzd6d44sdbwu5jcfrs3rz2a2@orquwgflrtyc/ > > > > I'm not sure this alert can actually work as a result :( > > I am struggling to come up with a scheme that will work. > > > Would it work if we change it to a level-triggered interrupt instead of edge > triggered? > > Since the main purpose of this is to trigger a hardware shutdown, perhaps we > could just omit the interrupt/emitting the event and keep the threshold and > enable attributes if we can't come up with a reasonable way to handle the > interrupts? > Hi Jonathan, and David, I think this is getting very complicated for something not that useful in practice. If needed we can go back on this later to find an appropriate solution. I sent a non RFC V3 version, removing the interrupt handling? Does that work for you? Cheers Julein
