linux-kernel - Re: [PATCH v2 2/2] iio: accel: adxl380: Optimize reading of FIFO entries in interrupt handler

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Message-ID: <20260123095417.31b11fd6@jic23-huawei>
Date: Fri, 23 Jan 2026 09:54:17 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: Francesco Lavra <flavra@...libre.com>, Ramona Gradinariu
 <ramona.gradinariu@...log.com>, Antoniu Miclaus
 <antoniu.miclaus@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, Michael
 Hennerich <Michael.Hennerich@...log.com>, David Lechner
 <dlechner@...libre.com>, Nuno Sá <nuno.sa@...log.com>, Andy
 Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: accel: adxl380: Optimize reading of FIFO
 entries in interrupt handler

On Fri, 23 Jan 2026 10:13:16 +0200
Andy Shevchenko <andriy.shevchenko@...el.com> wrote:

> On Thu, Jan 22, 2026 at 07:53:13PM +0000, Jonathan Cameron wrote:
> > On Mon, 19 Jan 2026 11:23:17 +0100
> > Francesco Lavra <flavra@...libre.com> wrote:
> >   
> > > In order to minimize the time required for transferring FIFO data from the
> > > sensor to the host machine, perform the read from the FIFO in a single call
> > > to regmap_bulk_read().  
> 
> > It's a call to regmap_noinc_read()  not regmap_bulk_read()
> > I'll fix it.  
> 
> This is interesting, does it mean the patch was never tested on the real HW?
> Or maybe noninc is intentional?
> 
It's absolutely intentional.  The device presents a single register address
that has the fifo behind it (which is what we added noinc for years ago).
So patch should definitely work.  Goes from reading that register N times in
each call within a loop of M to reading it N x M.

If regcache is in use this makes a difference as avoids corrupting registers
after this point as the address increment expected in the hardware for
a bulk read doesn't happen.  Without regcache it's just "documentation" as
at least for protocols used here its the same as a bulk read on the bus.

So patch is fine, it just mentioned the wrong call in the description
I'd guess this is because someone is working with a tree that has the wrong call in
it but might be wrong.

Jonathan