linux-kernel - Re: [PATCH v1] iio: adc: ad_sigma_delta: Clear pending interrupts before enable

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Date: Mon, 08 Apr 2024 10:31:21 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, Markus Burri <markus.burri@...com>
Cc: linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>,
 linux-iio@...r.kernel.org, Nuno Sa <nuno.sa@...log.com>
Subject: Re: [PATCH v1] iio: adc: ad_sigma_delta: Clear pending interrupts
 before enable

On Sat, 2024-04-06 at 17:17 +0100, Jonathan Cameron wrote:
> On Thu,  4 Apr 2024 19:51:26 +0200
> Markus Burri <markus.burri@...com> wrote:
> 
> Hi Markus,
> 
> 
> > For device will enable and disable irq contiously like AD7195,
> > it use DOUT/RDY pin for both SPI transfer and data ready.
> > It will disable irq during SPI transfer, and re-eanble irq after SPI
> > transfer.
> > That may cause irq status bit set to 1 during spi transfer.
> 
> Superficially that sounds like it might be an irq driver bug to me...
> Or just possibly an irq chip doing lazy disabling?

Yes, this sounds odd as we are already explicitly disabling lazy disabling:

https://elixir.bootlin.com/linux/latest/source/drivers/iio/adc/ad_sigma_delta.c#L589

> 
> > 
> > When the active condition has been detected, the corresponding bit
> > remains set until cleared by software. Status flags are cleared
> > by writing a 1 to the corresponding bit position.
> > 
> > Signed-off-by: Markus Burri <markus.burri@...com>
> 
> I'll need an appropriate ADI ack for this one.
> 

Yeah, I wanted to reply to this one Friday but then completely forgot. I can't
really ack this one. I would need some insights from someone with more core IRQ
knowledge. But...

> It seems highly unusual to be calling a generic irqchip related function in a
> driver (there are no other such users).  So this seems unlikely to be
> the right fix for this particular problem.
> 

Yes, and this (I think) would not even fix (if a fix is needed) this for all
irqchips which to me already sounds not the way to go.

- Nuno Sá
>