From: Jonathan Cameron <jic23@kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>,
linux-iio@vger.kernel.org,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Linux I2C <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH] iio: adc: max9611: Defer probe on POR read
Date: Sun, 10 Nov 2019 17:15:26 +0000 [thread overview]
Message-ID: <20191110171526.2bd269a9@archlinux> (raw)
In-Reply-To: <CAMuHMdUH0LrZ6iEuN1aWCTt_-jpgp=EjxubMAVdp11HLL=ayyQ@mail.gmail.com>
On Thu, 17 Oct 2019 14:55:58 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Jacopo,
>
> CC i2c
Ping. Wolfram, a query in here for you.
Thanks,
Jonathan
>
> On Wed, Oct 16, 2019 at 12:23 PM Jacopo Mondi <jacopo+renesas@jmondi.org> wrote:
> > The max9611 driver tests communications with the chip by reading the die
> > temperature during the probe function. If the temperature register
> > POR (power-on reset) value is returned from the test read, defer probe to
> > give the chip a bit more time to properly exit from reset.
> >
> > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>
> Thanks for your patch!
>
> > Geert,
> > I've not been able to reproduce the issue on my boards (M3-N
> > Salvator-XS and M3-W Salvator-X). As you reported the issue you might be
> > able to reproduce it, could you please test this?
>
> I can reproduce it on Salvator-XS with R-Car H3 ES2.0.
> According to my logs, I've seen the issue on all Salvator-X(S) boards,
> but not with the same frequency. Probability is highest on H3 ES2.0
> (ca. 5% of the boots since I first saw the issue), followed by H3 ES1.0,
> M3-W, and M3-N.
>
> After more investigation, my findings are:
> 1. I cannot reproduce the issue if the max9611 driver is modular.
> Is it related to using max9611 "too soon" after i2c bus init?
> How can "i2c bus init" impact a slave device?
> Perhaps due to pin configuration, e.g. changing from another pin
> function or GPIO to function i2c4?
> 2. Adding a delay at the top of max9611_init() fixes the issue.
> This would explain why the issue is less likely to happy on slower
> SoCs like M3-N.
> 3. Disabling all other i2c slaves on i2c4 in DTS fixes the issue.
> Before, max9611 was initialized last, so this moves init earlier,
> contradicting theory #1.
> 4. Just disabling the adv7482 (which registers 11 dummies i2c slaves)
> in DTS does not fix the issue.
>
> Unfortunately i2c4 is exposed on a 60-pin Samtec QSH connector only,
> for which I have no breakout adapter.
>
> Wolfram: do you have any clues?
>
> > Also, I opted for deferring probe instead of arbitrary repeat the
> > temperature read. What's your opinion?
>
> While this is probably OK if the max9611 driver is built-in, I'm afraid
> this may lead to unbounded delays for a reprobe in case the driver
> is modular.
>
> > --- a/drivers/iio/adc/max9611.c
> > +++ b/drivers/iio/adc/max9611.c
> > @@ -80,6 +80,7 @@
> > * The complete formula to calculate temperature is:
> > * ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
> > */
> > +#define MAX9611_TEMP_POR 0x8000
> > #define MAX9611_TEMP_MAX_POS 0x7f80
> > #define MAX9611_TEMP_MAX_NEG 0xff80
> > #define MAX9611_TEMP_MIN_NEG 0xd980
> > @@ -480,8 +481,10 @@ static int max9611_init(struct max9611_dev *max9611)
> > if (ret)
> > return ret;
> >
> > - regval &= MAX9611_TEMP_MASK;
> > + if (regval == MAX9611_TEMP_POR)
> > + return -EPROBE_DEFER;
> >
> > + regval &= MAX9611_TEMP_MASK;
> > if ((regval > MAX9611_TEMP_MAX_POS &&
> > regval < MAX9611_TEMP_MIN_NEG) ||
> > regval > MAX9611_TEMP_MAX_NEG) {
>
> Gr{oetje,eeting}s,
>
> Geert
>
next prev parent reply other threads:[~2019-11-10 17:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-16 10:25 [PATCH] iio: adc: max9611: Defer probe on POR read Jacopo Mondi
2019-10-17 12:55 ` Geert Uytterhoeven
2019-11-10 17:15 ` Jonathan Cameron [this message]
2019-11-10 18:45 ` Geert Uytterhoeven
2019-11-13 9:41 ` Geert Uytterhoeven
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191110171526.2bd269a9@archlinux \
--to=jic23@kernel.org \
--cc=geert@linux-m68k.org \
--cc=jacopo+renesas@jmondi.org \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=wsa+renesas@sang-engineering.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).