From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: "Alessandro Zummo" <a.zummo@towertech.it>,
"Andrew Jeffery" <andrew@aj.id.au>,
"Fabio Estevam" <fabio.estevam@nxp.com>,
"Joel Stanley" <joel@jms.id.au>,
"Mark Rutland" <mark.rutland@arm.com>,
"Rob Herring" <robh+dt@kernel.org>,
"Russell King" <linux@armlinux.org.uk>,
"Sascha Hauer" <s.hauer@pengutronix.de>,
"Shawn Guo" <shawnguo@kernel.org>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-rtc@vger.kernel.org, "Søren Andersen" <san@skov.dk>
Subject: Re: [PATCH v1 4/5] rtc: pcf8523: external capacitor configuration
Date: Thu, 13 Sep 2018 21:27:13 +0200 [thread overview]
Message-ID: <20180913192713.GJ14988@piout.net> (raw)
In-Reply-To: <20180907193508.24974-5-sam@ravnborg.org>
On 07/09/2018 21:35:07+0200, Sam Ravnborg wrote:
> From: Søren Andersen <san@skov.dk>
>
> Add support for specifying the quartz load in the DT node.
> The pcf8523 may use either a 7 pF or an 12.5 pF xtal.
> If the rtc has the wrong configuration the time will
> drift several hours/week.
>
> If nothing is specified in DT then the factory default of 7 pF is used.
> This is a change compared to before where the driver assumed 12.5 pF.
>
> Note: all kernel dts trees are updated with the new property.
>
> Signed-off-by: Søren Andersen <san@skov.dk>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Cc: Alessandro Zummo <a.zummo@towertech.it>
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
> drivers/rtc/rtc-pcf8523.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/rtc/rtc-pcf8523.c b/drivers/rtc/rtc-pcf8523.c
> index 453615f8ac9a..3c19b4d21a2d 100644
> --- a/drivers/rtc/rtc-pcf8523.c
> +++ b/drivers/rtc/rtc-pcf8523.c
> @@ -85,7 +85,7 @@ static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
> return 0;
> }
>
> -static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
> +static int pcf8523_select_capacitance(struct i2c_client *client)
> {
> u8 value;
> int err;
> @@ -94,7 +94,7 @@ static int pcf8523_select_capacitance(struct i2c_client *client, bool high)
> if (err < 0)
> return err;
>
> - if (!high)
> + if (!device_property_present(&client->dev, "nxp,quartz_load_12.5pf"))
OK, this is super annoying we unfortunately can't change what was done
previously without breaking the DT ABI. Honestly, I suspect the 12.5pF
value is wrong for most boards anyway.
What I would do is use the value from DT (so either 7000fF or 12500fF)
and set it if present.
If not present, set 12.5pF and print a warning that this differs from
the RTC default.
Hopefully, at some point, we could leave it as it is as the value should
persist across reboot.
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
next prev parent reply other threads:[~2018-09-14 0:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180822183555.GA24084@ravnborg.org>
2018-09-07 19:35 ` [PATCH v1 0/5] add quartz load support to NXP rtc drivers Sam Ravnborg
2018-09-07 19:35 ` [PATCH v1 1/5] dt-binding: rtci-pcf8523: add quartz_load property Sam Ravnborg
2018-09-07 21:43 ` Sam Ravnborg
2018-09-13 19:05 ` Alexandre Belloni
2018-09-13 20:44 ` Sam Ravnborg
2018-09-13 20:51 ` Alexandre Belloni
2018-09-26 15:47 ` Rob Herring
2018-09-26 18:51 ` Alexandre Belloni
2018-09-26 20:42 ` Sam Ravnborg
2018-09-07 19:35 ` [PATCH v1 2/5] dt-binding: rtc-pcf85063: add quartz load property Sam Ravnborg
2018-09-13 19:11 ` Alexandre Belloni
2018-09-07 19:35 ` [PATCH v1 3/5] dts: add nxp,quartz_load_12.5pf to all pcf8523 nodes Sam Ravnborg
2018-09-13 19:14 ` Alexandre Belloni
2018-09-07 19:35 ` [PATCH v1 4/5] rtc: pcf8523: external capacitor configuration Sam Ravnborg
2018-09-13 19:27 ` Alexandre Belloni [this message]
2018-09-07 19:35 ` [PATCH v1 5/5] rtc: pcf85063: " Sam Ravnborg
2018-09-13 19:29 ` Alexandre Belloni
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