Re: [PATCH] rtc: add support for rtc NXP pca21125

[Alexandre Belloni]

Hi,

Don't forget to Cc the rtc-linux mailing list.

Also, please please run checkpatch on your patches

On 18/10/2016 at 07:47:24 -0700, VENKAT PRASHANTH B U wrote :
> This is the patch to add support for
> NXP rtc pca21125
> 
> Signed-off-by: Venkat Prashanth B U <venkat.prashanth2498@xxxxxxxxx>
> ---
> ---
>  drivers/rtc/Kconfig        |  12 ++++
>  drivers/rtc/Makefile       |   1 +
>  drivers/rtc/rtc-pca21125.c | 164 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 177 insertions(+)
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index e215f50..df10e0e 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -686,6 +686,18 @@ config RTC_DRV_MAX6916
>  	  This driver can also be built as a module. If so, the module
>  	  will be called rtc-max6916.
>  
> +config RTC_DRV_PCA21125
> +	tristate "NXP PCA21125"
> +	help
> +	  If you say yes here you will get support for the
> +	  NXP PCA21125 SPI RTC chip.
> +
> +	  This driver only supports the RTC feature, and not other chip
> +	  features such as alarms.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rtc-pca21125.
> +
>  config RTC_DRV_R9701
>  	tristate "Epson RTC-9701JE"
>  	help
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 7cf7ad5..2c6af37 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -105,6 +105,7 @@ obj-$(CONFIG_RTC_DRV_NUC900)	+= rtc-nuc900.o
>  obj-$(CONFIG_RTC_DRV_OMAP)	+= rtc-omap.o
>  obj-$(CONFIG_RTC_DRV_OPAL)	+= rtc-opal.o
>  obj-$(CONFIG_RTC_DRV_PALMAS)	+= rtc-palmas.o
> +obj-$(CONFIG_RTC_DRV_PCA21125)	+= rtc-pca21125.o
>  obj-$(CONFIG_RTC_DRV_PCAP)	+= rtc-pcap.o
>  obj-$(CONFIG_RTC_DRV_PCF2123)	+= rtc-pcf2123.o
>  obj-$(CONFIG_RTC_DRV_PCF2127)	+= rtc-pcf2127.o
> diff --git a/drivers/rtc/rtc-pca21125.c b/drivers/rtc/rtc-pca21125.c
> index e69de29..8d42e4e 100644
> --- a/drivers/rtc/rtc-pca21125.c
> +++ b/drivers/rtc/rtc-pca21125.c
The whole file is badly indented

> @@ -0,0 +1,164 @@
> +	/* rtc-pca21125.c
> +	*
> +	* Driver for NXP  PCA21125 CMOS, SPI Compatible
> +	* Real Time Clock
> +	*
> +	* Author : Venkat Prashanth B U <venkat.prashanth2498@xxxxxxxxx>
> +	*
> +	* This program is free software; you can redistribute it and/or modify
> +	* it under the terms of the GNU General Public License version 2 as
> +	* published by the Free Software Foundation.
> +	*
> +	*/
> +	
> +	#include <linux/init.h>
> +	#include <linux/module.h>
> +	#include <linux/device.h>
> +	#include <linux/platform_device.h>
> +	#include <linux/rtc.h>
> +	#include <linux/spi/spi.h>
> +	#include <linux/bcd.h>
> +	
> +	/* Registers in pca21125 rtc */
> +	
> +	#define PCA21125_SECONDS_REG	0x02
> +	#define PCA21125_MINUTES_REG	0x03
> +	#define PCA21125_HOURS_REG		0x04
> +	#define PCA21125_DATE_REG		0x05
> +	#define PCA21125_DAY_REG		0x06
> +	#define PCA21125_MONTH_REG		0x07
> +	#define PCA21125_YEAR_REG		0x08

Those are defined but not used

> +	#define PCA21125_CONTROL_REG	0x01
> +	#define PCA21125_STATUS_REG	0x00
> +	#define PCA21125_CLOCK_BURST	0x0D
> +	
> +	static int pca21125_read_reg(struct device *dev, unsigned char address,
> +					unsigned char *data)
> +	{
> +		struct spi_device *spi = to_spi_device(dev);
> +	
> +		*data = address | 0x80;
> +	
> +		return spi_write_then_read(spi, data, 1, data, 1);
> +	}
> +	
> +	static int pca21125_write_reg(struct device *dev, unsigned char address,
> +					unsigned char data)
> +	{
> +		struct spi_device *spi = to_spi_device(dev);
> +		unsigned char buf[2];
> +	
> +		buf[0] = address & 0x7F;
> +		buf[1] = data;
> +	
> +		return spi_write_then_read(spi, buf, 2, NULL, 0);
> +	}
> +	
> +	static int pca21125_read_time(struct device *dev, struct rtc_time *dt)
> +	{
> +		struct spi_device *spi = to_spi_device(dev);
> +		int err;
> +		unsigned char buf[8];
> +	
> +		buf[0] = PCA21125_CLOCK_BURST | 0x80;
> +	
> +		err = spi_write_then_read(spi, buf, 1, buf, 8);
> +	
> +		if (err)
> +			return err;
> +	

I'm not sure to understand how this can actually work, time/date starts
at 0x2

> +		dt->tm_sec = bcd2bin(buf[0]);
> +		dt->tm_min = bcd2bin(buf[1]);
> +		dt->tm_hour = bcd2bin(buf[2] & 0x3F);
> +		dt->tm_mday = bcd2bin(buf[3]);
> +		dt->tm_mon = bcd2bin(buf[4]) - 1;
> +		dt->tm_wday = bcd2bin(buf[5]) - 1;
> +		dt->tm_year = bcd2bin(buf[6]) + 100;
> +	
> +		return rtc_valid_tm(dt);
> +	}
> +	
> +	static int pca21125_set_time(struct device *dev, struct rtc_time *dt)
> +	{
> +		struct spi_device *spi = to_spi_device(dev);
> +		unsigned char buf[9];
> +	
> +		if (dt->tm_year < 100 || dt->tm_year > 199) {
> +			dev_err(&spi->dev, "Year must be between 2000 and 2099. It's %d.\n",
> +				dt->tm_year + 1900);
> +		return -EINVAL;
> +		}
> +	
> +		buf[0] = bin2bcd(dt->tm_sec);
> +		buf[1] = bin2bcd(dt->tm_min);
> +		buf[2] = (bin2bcd(dt->tm_hour) & 0X3F);
> +		buf[3] = bin2bcd(dt->tm_mday);
> +		buf[4] = bin2bcd(dt->tm_mon + 1);
> +		buf[5] = bin2bcd(dt->tm_wday + 1);
> +		buf[6] = bin2bcd(dt->tm_year % 100);
> +		buf[7] = bin2bcd(0x00);
> +	

Isn't it necessary to write the address on the bus first? How does that
work?

> +		/* write the rtc settings */
> +		return spi_write_then_read(spi, buf, 9, NULL, 0);
> +	}
> +	
> +	static const struct rtc_class_ops pca21125_rtc_ops = {
> +		.read_time = pca21125_read_time,
> +		.set_time = pca21125_set_time,
> +	};
> +	
> +	static int pca21125_probe(struct spi_device *spi)
> +	{
> +		struct rtc_device *rtc;
> +		unsigned char data;
> +		int res;
> +	
> +		/* spi setup with pca21125 in mode 3 and bits per word as 8 */
> +		spi->mode = SPI_MODE_3;
> +		spi->bits_per_word = 8;
> +		spi_setup(spi);
> +	
> +		/* RTC Settings */
> +		res = pca21125_read_reg(&spi->dev, PCA21125_SECONDS_REG, &data);
> +		if (res)
> +			return res;
> +	

Is that read useful?

> +		/* Disable the write protect of rtc */
> +		pca21125_read_reg(&spi->dev, PCA21125_CONTROL_REG, &data);
> +		data = data & ~(1 << 7);

This is a magic value, please use a define

> +		pca21125_write_reg(&spi->dev, PCA21125_CONTROL_REG, data);
> +	
> +		/*Enable oscillator,disable oscillator stop flag, glitch filter*/
> +		pca21125_read_reg(&spi->dev, PCA21125_STATUS_REG, &data);
> +		data = data & 0x1B;

ditto

> +		pca21125_write_reg(&spi->dev, PCA21125_STATUS_REG, data);
> +	
> +		/* display the settings */
> +		pca21125_read_reg(&spi->dev, PCA21125_CONTROL_REG, &data);
> +		dev_info(&spi->dev, "PCA21125 RTC CTRL Reg = 0x%02x\n", data);
> +	

I don't think anybody actually cares about that information

> +		pca21125_read_reg(&spi->dev, PCA21125_STATUS_REG, &data);
> +		dev_info(&spi->dev, "PCA21125 RTC Status Reg = 0x%02x\n", data);
> +	

ditto

> +		rtc = devm_rtc_device_register(&spi->dev, "pca21125",
> +							&pca21125_rtc_ops, THIS_MODULE);
> +		if (IS_ERR(rtc))
> +			return PTR_ERR(rtc);
> +	
> +		spi_set_drvdata(spi, rtc);
> +	
> +		return 0;
> +	}
> +	
> +	static struct spi_driver pca21125_driver = {
> +		.driver = {
> +			.name = "pca21125",
> +		},
> +		.probe = pca21125_probe,
> +	};
> +	module_spi_driver(pca21125_driver);
> +	
> +	MODULE_DESCRIPTION("PCA21125 SPI RTC DRIVER");
> +	MODULE_AUTHOR("Venkat Prashanth B U <venkat.prashanth2498@xxxxxxxxx>");
> +	MODULE_LICENSE("GPL v2");
> +	
> -- 
> 1.9.2
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com