linux-kernel - Re: [PATCH] rtc: ds1307: add basic support for ds1341 chip

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Date:   Wed, 23 Aug 2017 17:12:03 +0200
From:   Aleksander Morgado <aleksander@...ksander.es>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnaud Ebalard <arno@...isbad.org>,
        David Lowe <dave-lowe@...world.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Marek Vasut <marex@...x.de>, Tin Huynh <tnhuynh@....com>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrey Smirnov <andrew.smirnov@...il.com>,
        Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH] rtc: ds1307: add basic support for ds1341 chip

On 23/08/17 07:38, Nikita Yushchenko wrote:
> This adds support for reading and writing date/time from/to ds1314 chip.
> 
> Other functionality (alarms, inout clock, output clock) is not added
> yet, because availability of that depends on chip connections.
> 
> Signed-off-by: Nikita Yushchenko <nikita.yoush@...entembedded.com>

Tested this patch on a ZII RDU2 and it seems to work properly.

Tested-by: Aleksander Morgado <aleksander@...ksander.es

> ---
>  drivers/rtc/Kconfig      | 10 +++++-----
>  drivers/rtc/rtc-ds1307.c | 13 +++++++++++++
>  2 files changed, 18 insertions(+), 5 deletions(-)
> ===
> DS1341/1342 chips have additional features, namely
> - alarms,
> - input clock (can be used instead of intercal oscillator for better
>   accuracy),
> - output clock ("square wave generation")
> 
> However, not all of that is available at the same time. Same chip pins,
> CLKIN/nINTA and SQW/nINTB, can be used either for input/output clocks,
> or for alarm interrupts. Role of these pins on particular board depends
> on hardware wiring.
> 
> We can add device tree properties that describe if each of pins is wired
> as clock, or as interrupt, or left unconnected, and enable support for
> corresponding functionality based on that. But that requires hardware setups
> for testing, and also is somewhat cumbersome. Additional complexity is
> caused by bit enabling/disabling output clock also affects which pins alarm
> interrupts are routed to.
> 
> Another factor is that there are hardware setups (i.e. ZII RDU2) that
> power DS1341 from SuperCap, which makes power saving critical. For such
> setups, kernel driver should leave register bits that control mentioned
> pins in the state configured by bootloader.
> 
> Given all that, it was decided to limit support to "only date/time" for
> now. That is enough for common use case. Full (and cumbersome) implementation
> can be added later if ever needed.
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index 72419ac2c52a..db63592a0f57 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -227,14 +227,14 @@ config RTC_DRV_AS3722
>  	  will be called rtc-as3722.
>  
>  config RTC_DRV_DS1307
> -	tristate "Dallas/Maxim DS1307/37/38/39/40, ST M41T00, EPSON RX-8025, ISL12057"
> +	tristate "Dallas/Maxim DS1307/37/38/39/40/41, ST M41T00, EPSON RX-8025, ISL12057"
>  	help
>  	  If you say yes here you get support for various compatible RTC
>  	  chips (often with battery backup) connected with I2C. This driver
> -	  should handle DS1307, DS1337, DS1338, DS1339, DS1340, ST M41T00,
> -	  EPSON RX-8025, Intersil ISL12057 and probably other chips. In some
> -	  cases the RTC must already have been initialized (by manufacturing or
> -	  a bootloader).
> +	  should handle DS1307, DS1337, DS1338, DS1339, DS1340, DS1341,
> +	  ST M41T00, EPSON RX-8025, Intersil ISL12057 and probably other chips.
> +	  In some cases the RTC must already have been initialized (by
> +	  manufacturing or a bootloader).
>  
>  	  The first seven registers on these chips hold an RTC, and other
>  	  registers may add features such as NVRAM, a trickle charger for
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 4fac49e55d47..1d11f8000f8a 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -39,6 +39,7 @@ enum ds_type {
>  	ds_1338,
>  	ds_1339,
>  	ds_1340,
> +	ds_1341,
>  	ds_1388,
>  	ds_3231,
>  	m41t0,
> @@ -179,6 +180,10 @@ static struct chip_desc chips[last_ds_type] = {
>  		.century_bit	= DS1340_BIT_CENTURY,
>  		.trickle_charger_reg = 0x08,
>  	},
> +	[ds_1341] = {
> +		.century_reg	= DS1307_REG_MONTH,
> +		.century_bit	= DS1337_BIT_CENTURY,
> +	},
>  	[ds_1388] = {
>  		.trickle_charger_reg = 0x0a,
>  	},
> @@ -209,6 +214,7 @@ static const struct i2c_device_id ds1307_id[] = {
>  	{ "ds1339", ds_1339 },
>  	{ "ds1388", ds_1388 },
>  	{ "ds1340", ds_1340 },
> +	{ "ds1341", ds_1341 },
>  	{ "ds3231", ds_3231 },
>  	{ "m41t0", m41t0 },
>  	{ "m41t00", m41t00 },
> @@ -253,6 +259,10 @@ static const struct of_device_id ds1307_of_match[] = {
>  		.data = (void *)ds_1340
>  	},
>  	{
> +		.compatible = "dallas,ds1341",
> +		.data = (void *)ds_1341
> +	},
> +	{
>  		.compatible = "maxim,ds3231",
>  		.data = (void *)ds_3231
>  	},
> @@ -298,6 +308,7 @@ static const struct acpi_device_id ds1307_acpi_ids[] = {
>  	{ .id = "DS1339", .driver_data = ds_1339 },
>  	{ .id = "DS1388", .driver_data = ds_1388 },
>  	{ .id = "DS1340", .driver_data = ds_1340 },
> +	{ .id = "DS1341", .driver_data = ds_1341 },
>  	{ .id = "DS3231", .driver_data = ds_3231 },
>  	{ .id = "M41T0", .driver_data = m41t0 },
>  	{ .id = "M41T00", .driver_data = m41t00 },
> @@ -1323,6 +1334,7 @@ static int ds1307_probe(struct i2c_client *client,
>  	static const int	bbsqi_bitpos[] = {
>  		[ds_1337] = 0,
>  		[ds_1339] = DS1339_BIT_BBSQI,
> +		[ds_1341] = 0,
>  		[ds_3231] = DS3231_BIT_BBSQW,
>  	};
>  	const struct rtc_class_ops *rtc_ops = &ds13xx_rtc_ops;
> @@ -1401,6 +1413,7 @@ static int ds1307_probe(struct i2c_client *client,
>  	switch (ds1307->type) {
>  	case ds_1337:
>  	case ds_1339:
> +	case ds_1341:
>  	case ds_3231:
>  		/* get registers that the "rtc" read below won't read... */
>  		err = regmap_bulk_read(ds1307->regmap, DS1337_REG_CONTROL,
> 


-- 
Aleksander
https://aleksander.es