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

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Date: Sat, 13 Apr 2024 16:56:36 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Nuno Sá <noname.nuno@...il.com>
Cc: Markus Burri <markus.burri@...com>, 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 Mon, 08 Apr 2024 10:31:21 +0200
Nuno Sá <noname.nuno@...il.com> wrote:

> 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

Markus, can you confirm you are running no a kernel with that line present?
Maybe this is just an old kernel not having the fix?

> 
> >   
> > > 
> > > 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
> >