On Fri, Nov 22, 2024 at 1:34 PM Uwe Kleine-König
<u.kleine-koenig@xxxxxxxxxxxx> wrote:
>
> Some of the ADCs by Analog signal their irq condition on the MISO line.
> So typically that line is connected to an SPI controller and a GPIO. The
> GPIO is used as input and the respective interrupt is enabled when the
> last SPI transfer is completed.
>
> Depending on the GPIO controller the toggling MISO line might make the
> interrupt pending even while it's masked. In that case the irq handler
> is called immediately after irq_enable() and so before the device
> actually pulls that line low which results in non-sense values being
> reported to the upper layers.
>
> The only way to find out if the line was actually pulled low is to read
> the GPIO. (There is a flag in AD7124's status register that also signals
> if an interrupt was asserted, but reading that register toggles the MISO
> line and so might trigger another spurious interrupt.)
>
> Add the possibility to specify an interrupt GPIO in the machine
> description in addition to the plain interrupt. This GPIO is used then
> to check if the irq line is actually active in the irq handler.
...
> + if (!sigma_delta->rdy_gpiod || gpiod_get_value(sigma_delta->rdy_gpiod)) {
> + complete(&sigma_delta->completion);
> + disable_irq_nosync(irq);
> + sigma_delta->irq_dis = true;
> + iio_trigger_poll(sigma_delta->trig);
> +
> + return IRQ_HANDLED;
> + } else {
Redundant 'else'.
> + return IRQ_NONE;
> + }
Can we actually invert the conditional?
> }
...
> + if (sigma_delta->rdy_gpiod && !sigma_delta->irq_line)
Do you need the first check? (I haven't remember what gpiod_to_irq()
will return on NULL, though)
> + sigma_delta->irq_line = gpiod_to_irq(sigma_delta->rdy_gpiod);
...
> --- a/include/linux/iio/adc/ad_sigma_delta.h
> +++ b/include/linux/iio/adc/ad_sigma_delta.h
> @@ -96,6 +96,7 @@ struct ad_sigma_delta {
> unsigned int active_slots;
> unsigned int current_slot;
> unsigned int num_slots;
> + struct gpio_desc *rdy_gpiod;
Do you need a type forward declaration?
> int irq_line;
> bool status_appended;
--
With Best Regards,
Andy Shevchenko
