Re: [PATCH RESEND v5 1/6] rtc: ls2x: Add support for the Loongson-2K/LS7A RTC

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

Hello,

On 24/08/2021 00:31:37+0800, WANG Xuerui wrote:
> This RTC module is integrated into the Loongson-2K SoC and the LS7A
> bridge chip. This version is almost entirely rewritten to make use of
> current kernel API.
> 
> Signed-off-by: Huacai Chen <chenhuacai@kernel.org>
> Signed-off-by: WANG Xuerui <git@xen0n.name>
> Tested-by: Jiaxun Yang <jiaxun.yang@flygoat.com> # loongson2k
> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Cc: devicetree@vger.kernel.org
> Cc: linux-mips@vger.kernel.org
> ---
>  drivers/rtc/Kconfig    |  11 +++
>  drivers/rtc/Makefile   |   1 +
>  drivers/rtc/rtc-ls2x.c | 180 +++++++++++++++++++++++++++++++++++++++++

Note that I'm still concerned this duplicates rtc-ls1x.c

>  3 files changed, 192 insertions(+)
>  create mode 100644 drivers/rtc/rtc-ls2x.c
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index daff06707455..819f366b4d91 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -1313,6 +1313,17 @@ config RTC_DRV_NTXEC
>  	  embedded controller found in certain e-book readers designed by the
>  	  original design manufacturer Netronix.
>  
> +config RTC_DRV_LS2X
> +	tristate "Loongson LS2X RTC"
> +	depends on OF && MACH_LOONGSON64 || COMPILE_TEST
> +	select REGMAP_MMIO
> +	help
> +	  If you say yes here you get support for the RTC on the Loongson-2K
> +	  SoC and LS7A bridge, which first appeared on the Loongson-2H.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rtc-ls2x.
> +
>  comment "on-CPU RTC drivers"
>  
>  config RTC_DRV_ASM9260
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
> index 5ceeafe4d5b2..98e68484f519 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -83,6 +83,7 @@ obj-$(CONFIG_RTC_DRV_LOONGSON1)	+= rtc-ls1x.o
>  obj-$(CONFIG_RTC_DRV_LP8788)	+= rtc-lp8788.o
>  obj-$(CONFIG_RTC_DRV_LPC24XX)	+= rtc-lpc24xx.o
>  obj-$(CONFIG_RTC_DRV_LPC32XX)	+= rtc-lpc32xx.o
> +obj-$(CONFIG_RTC_DRV_LS2X)	+= rtc-ls2x.o
>  obj-$(CONFIG_RTC_DRV_M41T80)	+= rtc-m41t80.o
>  obj-$(CONFIG_RTC_DRV_M41T93)	+= rtc-m41t93.o
>  obj-$(CONFIG_RTC_DRV_M41T94)	+= rtc-m41t94.o
> diff --git a/drivers/rtc/rtc-ls2x.c b/drivers/rtc/rtc-ls2x.c
> new file mode 100644
> index 000000000000..58901323b219
> --- /dev/null
> +++ b/drivers/rtc/rtc-ls2x.c
> @@ -0,0 +1,180 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Loongson-2K/7A RTC driver
> + *
> + * Based on the original out-of-tree Loongson-2H RTC driver for Linux 2.6.32,
> + * by Shaozong Liu <liushaozong@loongson.cn>.
> + *
> + * Maintained out-of-tree by Huacai Chen <chenhuacai@kernel.org>.
> + *
> + * Rewritten for mainline by WANG Xuerui <git@xen0n.name>.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/rtc.h>
> +
> +#define TOY_TRIM_REG   0x20
> +#define TOY_WRITE0_REG 0x24
> +#define TOY_WRITE1_REG 0x28
> +#define TOY_READ0_REG  0x2c
> +#define TOY_READ1_REG  0x30
> +#define TOY_MATCH0_REG 0x34
> +#define TOY_MATCH1_REG 0x38
> +#define TOY_MATCH2_REG 0x3c
> +#define RTC_CTRL_REG   0x40
> +#define RTC_TRIM_REG   0x60
> +#define RTC_WRITE0_REG 0x64
> +#define RTC_READ0_REG  0x68
> +#define RTC_MATCH0_REG 0x6c
> +#define RTC_MATCH1_REG 0x70
> +#define RTC_MATCH2_REG 0x74
> +
> +#define TOY_MON        GENMASK(31, 26)
> +#define TOY_DAY        GENMASK(25, 21)
> +#define TOY_HOUR       GENMASK(20, 16)
> +#define TOY_MIN        GENMASK(15, 10)
> +#define TOY_SEC        GENMASK(9, 4)
> +#define TOY_MSEC       GENMASK(3, 0)
> +
> +struct ls2x_rtc_priv {
> +	struct regmap *regmap;
> +};
> +
> +static const struct regmap_config ls2x_rtc_regmap_config = {
> +	.reg_bits = 32,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +};
> +
> +struct ls2x_rtc_regs {
> +	u32 reg0;
> +	u32 reg1;
> +};
> +
> +static inline void ls2x_rtc_regs_to_time(struct ls2x_rtc_regs *regs,
> +					 struct rtc_time *tm)
> +{
> +	tm->tm_year = regs->reg1;
> +	tm->tm_sec = FIELD_GET(TOY_SEC, regs->reg0);
> +	tm->tm_min = FIELD_GET(TOY_MIN, regs->reg0);
> +	tm->tm_hour = FIELD_GET(TOY_HOUR, regs->reg0);
> +	tm->tm_mday = FIELD_GET(TOY_DAY, regs->reg0);
> +	tm->tm_mon = FIELD_GET(TOY_MON, regs->reg0) - 1;
> +}
> +
> +static inline void ls2x_rtc_time_to_regs(struct rtc_time *tm,
> +					 struct ls2x_rtc_regs *regs)
> +{
> +	regs->reg0 = FIELD_PREP(TOY_SEC, tm->tm_sec);
> +	regs->reg0 |= FIELD_PREP(TOY_MIN, tm->tm_min);
> +	regs->reg0 |= FIELD_PREP(TOY_HOUR, tm->tm_hour);
> +	regs->reg0 |= FIELD_PREP(TOY_DAY, tm->tm_mday);
> +	regs->reg0 |= FIELD_PREP(TOY_MON, tm->tm_mon + 1);
> +	regs->reg1 = tm->tm_year;
> +}
> +
> +static int ls2x_rtc_read_time(struct device *dev, struct rtc_time *tm)
> +{
> +	struct ls2x_rtc_priv *priv = dev_get_drvdata(dev);
> +	struct ls2x_rtc_regs regs;
> +	int ret;
> +
> +	ret = regmap_read(priv->regmap, TOY_READ1_REG, &regs.reg1);
> +	if (unlikely(ret))
> +		return ret;
> +
> +	ret = regmap_read(priv->regmap, TOY_READ0_REG, &regs.reg0);
> +	if (unlikely(ret))
> +		return ret;
> +

I'm actually wondering why you read first TOY_READ1_REG then
TOY_READ0_REG. ls1x does the opposite and the ls1c datasheet I found
doesn't mention any latching happening. So unless latching is done on
TOY_READ1_REG, you could use regmap_bulk_read and simply avoid struct
ls2x_rtc_regs.
If there is no latching, you may need to read TOY_READ0_REG at least
twice. Because TOY_READ1_REG only contains the year, it is an issue only
on 31 of December and it will not be easy to reproduce.


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com