From: "Sabau, Radu bogdan" <Radu.Sabau@analog.com>
To: "David Lechner" <dlechner@baylibre.com>,
"Lars-Peter Clausen" <lars@metafoo.de>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
"Jonathan Cameron" <jic23@kernel.org>,
"Sa, Nuno" <Nuno.Sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"Uwe Kleine-König" <ukleinek@kernel.org>,
"Liam Girdwood" <lgirdwood@gmail.com>,
"Mark Brown" <broonie@kernel.org>,
"Linus Walleij" <linusw@kernel.org>,
"Bartosz Golaszewski" <brgl@kernel.org>,
"Philipp Zabel" <p.zabel@pengutronix.de>
Cc: "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-pwm@vger.kernel.org" <linux-pwm@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>
Subject: RE: [PATCH v3 4/4] iio: adc: ad4691: add SPI offload support
Date: Mon, 16 Mar 2026 13:31:19 +0000 [thread overview]
Message-ID: <LV9PR03MB84148D2AD53C977D5EB92E14F740A@LV9PR03MB8414.namprd03.prod.outlook.com> (raw)
In-Reply-To: <b8a9a56b-04cb-4bb3-8606-3d90d1aba721@baylibre.com>
> -----Original Message-----
> From: David Lechner <dlechner@baylibre.com>
> Sent: Saturday, March 14, 2026 9:37 PM
...
> > +
> > + if (args[0] != AD4691_TRIGGER_EVENT_BUSY &&
> > + args[0] != AD4691_TRIGGER_EVENT_DATA_READY)
>
> What is the difference between BUSY and DATA_READY?
>
Perhaps BUSY won't be used at all, since indeed this question got me
thinking of its necessity.
> > + return false;
> > +
...
> > + xfer[num_xfers].cs_change = 1;
> > + xfer[num_xfers].cs_change_delay.value = 1000;
>
> This needs an explantion of where the number comes from. I would expect
> 430 ns
> based on max value of t_CONV from the datasheet.
>
You are right about this. I was playing with this value at testing and
Forgot to change it back, my bad...
> > + xfer[num_xfers].cs_change_delay.unit =
...
> > + } else {
> > + /*
> > + * CNV_CLOCK_MODE: single transfer per channel (2-byte cmd
> +
> > + * 2-byte data = 4 bytes, one 32-bit SPI Engine DMA word).
> > + * AVG_IN registers are used; RX layout: [cmd_hi, cmd_lo,
> d_hi, d_lo]
>
> These comments are confusing. What it actually appears we are doing is
> doing a 16-bit write and then a 16-bit read. I assume we are doing it
> using 32-bit words for efficiny so that we only have 1/2 of the number
> of xfers required to do it separately.
>
> TX layout: [cmd_hi, cmd_lo, ignore, ignore]
> RX layout: [ignore, ignore, data_hi, data_lo]
>
I will make sure to update the comment as you are saying here, since
TX and RX should be explained separately. Having them both as
'RX layout' is a mistake.
>
> > + */
> > + for (i = 0; i < n_active; i++) {
> > + unsigned int reg;
> > + int ch = active_chans[i];
> > +
> > + reg = AD4691_AVG_IN(ch);
> > +
> put_unaligned_be32(FIELD_PREP(AD4691_MSG_ADDR_HI, (reg >> 8)
> | 0x80) |
>
> Mixing FIELD_PREP() and bit ops looks wrong.
Will stick to bit ops in this case, then.
next prev parent reply other threads:[~2026-03-16 13:31 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-13 10:07 [PATCH v3 0/4] iio: adc: ad4691: add driver for AD4691 multichannel SAR ADC family Radu Sabau via B4 Relay
2026-03-13 10:07 ` [PATCH v3 1/4] dt-bindings: iio: adc: add bindings for AD4691 family Radu Sabau via B4 Relay
2026-03-14 9:41 ` Krzysztof Kozlowski
2026-03-16 11:55 ` Sabau, Radu bogdan
2026-03-14 15:29 ` David Lechner
2026-03-14 16:19 ` David Lechner
2026-03-16 12:39 ` Sabau, Radu bogdan
2026-03-16 12:55 ` Sabau, Radu bogdan
2026-03-16 15:14 ` David Lechner
2026-03-16 15:47 ` Sabau, Radu bogdan
2026-03-14 18:18 ` David Lechner
2026-03-13 10:07 ` [PATCH v3 2/4] iio: adc: ad4691: add initial driver " Radu Sabau via B4 Relay
2026-03-13 10:58 ` Andy Shevchenko
2026-03-16 15:29 ` Sabau, Radu bogdan
2026-03-16 15:51 ` David Lechner
2026-03-16 15:57 ` Sabau, Radu bogdan
2026-03-16 16:13 ` Andy Shevchenko
2026-03-14 11:04 ` Nuno Sá
2026-03-16 14:29 ` Sabau, Radu bogdan
2026-03-16 16:00 ` Sabau, Radu bogdan
2026-03-14 16:36 ` David Lechner
2026-03-16 13:01 ` Sabau, Radu bogdan
2026-03-25 15:01 ` kernel test robot
2026-03-13 10:07 ` [PATCH v3 3/4] iio: adc: ad4691: add triggered buffer support Radu Sabau via B4 Relay
2026-03-13 11:13 ` Andy Shevchenko
2026-03-13 12:09 ` Sabau, Radu bogdan
2026-03-13 14:40 ` Andy Shevchenko
2026-03-14 18:37 ` David Lechner
2026-03-16 13:22 ` Sabau, Radu bogdan
2026-03-16 15:37 ` David Lechner
2026-03-16 15:56 ` Sabau, Radu bogdan
2026-03-16 16:44 ` David Lechner
2026-03-17 9:27 ` Sabau, Radu bogdan
2026-03-13 10:07 ` [PATCH v3 4/4] iio: adc: ad4691: add SPI offload support Radu Sabau via B4 Relay
2026-03-14 19:37 ` David Lechner
2026-03-16 13:31 ` Sabau, Radu bogdan [this message]
2026-03-13 11:14 ` [PATCH v3 0/4] iio: adc: ad4691: add driver for AD4691 multichannel SAR ADC family Andy Shevchenko
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