Re: [PATCH 1/4] rtc: ls2x: Add support for the Loongson-2K/LS7A RTC

[WANG Xuerui <kernel@xen0n.name>]

Hi Tiezhu,

On 2020/9/23 17:54, Tiezhu Yang wrote:
> On 09/23/2020 03:58 PM, 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 <chenhc@lemote.com>
>> Signed-off-by: WANG Xuerui <git@xen0n.name>
>> ---
>>   drivers/rtc/Kconfig    |  11 ++
>>   drivers/rtc/Makefile   |   1 +
>>   drivers/rtc/rtc-ls2x.c | 225 +++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 237 insertions(+)
>>   create mode 100644 drivers/rtc/rtc-ls2x.c
>>
>> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
>> index 48c536acd777..41b96633abf3 100644
>> --- a/drivers/rtc/Kconfig
>> +++ b/drivers/rtc/Kconfig
>> @@ -1301,6 +1301,17 @@ config RTC_DRV_CROS_EC
>>         This driver can also be built as a module. If so, the module
>>         will be called rtc-cros-ec.
>>   +config RTC_DRV_LS2X
>> +    tristate "Loongson LS2X RTC"
>> +    depends on 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.
>> +
>
> Hi Xuerui,
>
> rtc-ls2x --> rtc-ls2x-ls7a
> RTC_DRV_LS2X --> RTC_DRV_LS2X_LS7A
> Loongson LS2X RTC --> Loongson LS2X/LS7A RTC
>
> Maybe the related names include ls7a or LS7A is better to
> reflect the reality?
>
The RTC hardware blocks on Loongson 2H, 2K and LS7A all behave the same,
from every public documentation I can find. It is entirely reasonable
for a chip to behave like another, so I don't think the naming is a
problem on its own.

That said, if Loongson could start properly naming and versioning the
various peripheral blocks (of which there are already many revisions
with different quirks added/fixed), that would be a better way forward.
I remember seeing things along the line of "probe PRId" or even "see the
identification string on the chip package" in some Loongson FAQ docs,
just to probe some quirks, and that surely is not desirable...

> Thanks,
> Tiezhu
>
>>   comment "on-CPU RTC drivers"
>>     config RTC_DRV_ASM9260
>> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
>> index 880e08a409c3..ade72f6a2435 100644
>> --- a/drivers/rtc/Makefile
>> +++ b/drivers/rtc/Makefile
>> @@ -84,6 +84,7 @@ 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..e49cbaceccc2
>> --- /dev/null
>> +++ b/drivers/rtc/rtc-ls2x.c
>> @@ -0,0 +1,225 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Loongson-2K/7A RTC driver
>> + *
>> + * Based on the 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 <chenhc@lemote.com>.
>> + *
>> + * Rewritten for mainline by WANG Xuerui <git@xen0n.name>.
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>> +#include <linux/rtc.h>
>> +#include <linux/spinlock.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_MON_SHIFT  26
>> +#define TOY_DAY        GENMASK(25, 21)
>> +#define TOY_DAY_SHIFT  21
>> +#define TOY_HOUR       GENMASK(20, 16)
>> +#define TOY_HOUR_SHIFT 16
>> +#define TOY_MIN        GENMASK(15, 10)
>> +#define TOY_MIN_SHIFT  10
>> +#define TOY_SEC        GENMASK(9, 4)
>> +#define TOY_SEC_SHIFT  4
>> +#define TOY_MSEC       GENMASK(3, 0)
>> +#define TOY_MSEC_SHIFT 0
>> +
>> +struct ls2x_rtc_priv {
>> +    struct regmap *regmap;
>> +    spinlock_t lock;
>> +};
>> +
>> +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 = (regs->reg0 & TOY_SEC) >> TOY_SEC_SHIFT;
>> +    tm->tm_min = (regs->reg0 & TOY_MIN) >> TOY_MIN_SHIFT;
>> +    tm->tm_hour = (regs->reg0 & TOY_HOUR) >> TOY_HOUR_SHIFT;
>> +    tm->tm_mday = (regs->reg0 & TOY_DAY) >> TOY_DAY_SHIFT;
>> +    tm->tm_mon = ((regs->reg0 & TOY_MON) >> TOY_MON_SHIFT) - 1;
>> +}
>> +
>> +static inline void ls2x_rtc_time_to_regs(struct rtc_time *tm,
>> +                     struct ls2x_rtc_regs *regs)
>> +{
>> +    regs->reg0 = (tm->tm_sec << TOY_SEC_SHIFT) & TOY_SEC;
>> +    regs->reg0 |= (tm->tm_min << TOY_MIN_SHIFT) & TOY_MIN;
>> +    regs->reg0 |= (tm->tm_hour << TOY_HOUR_SHIFT) & TOY_HOUR;
>> +    regs->reg0 |= (tm->tm_mday << TOY_DAY_SHIFT) & TOY_DAY;
>> +    regs->reg0 |= ((tm->tm_mon + 1) << TOY_MON_SHIFT) & TOY_MON;
>> +    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;
>> +
>> +    spin_lock_irq(&priv->lock);
>> +
>> +    ret = regmap_read(priv->regmap, TOY_READ1_REG, &regs.reg1);
>> +    if (unlikely(ret)) {
>> +        dev_err(dev, "Failed to read time: %d\n", ret);
>> +        goto fail;
>> +    }
>> +
>> +    ret = regmap_read(priv->regmap, TOY_READ0_REG, &regs.reg0);
>> +    if (unlikely(ret)) {
>> +        dev_err(dev, "Failed to read time: %d\n", ret);
>> +        goto fail;
>> +    }
>> +
>> +    spin_unlock_irq(&priv->lock);
>> +
>> +    ls2x_rtc_regs_to_time(&regs, tm);
>> +
>> +    return 0;
>> +
>> +fail:
>> +    spin_unlock_irq(&priv->lock);
>> +    return ret;
>> +}
>> +
>> +static int ls2x_rtc_set_time(struct device *dev, struct rtc_time *tm)
>> +{
>> +    struct ls2x_rtc_priv *priv = dev_get_drvdata(dev);
>> +    struct ls2x_rtc_regs regs;
>> +    int ret;
>> +
>> +    ls2x_rtc_time_to_regs(tm, &regs);
>> +
>> +    spin_lock_irq(&priv->lock);
>> +
>> +    ret = regmap_write(priv->regmap, TOY_WRITE0_REG, regs.reg0);
>> +    if (unlikely(ret)) {
>> +        dev_err(dev, "Failed to set time: %d\n", ret);
>> +        goto fail;
>> +    }
>> +
>> +    ret = regmap_write(priv->regmap, TOY_WRITE1_REG, regs.reg1);
>> +    if (unlikely(ret)) {
>> +        dev_err(dev, "Failed to set time: %d\n", ret);
>> +        goto fail;
>> +    }
>> +
>> +    spin_unlock_irq(&priv->lock);
>> +
>> +    return 0;
>> +
>> +fail:
>> +    spin_unlock_irq(&priv->lock);
>> +    return ret;
>> +}
>> +
>> +static struct rtc_class_ops ls2x_rtc_ops = {
>> +    .read_time = ls2x_rtc_read_time,
>> +    .set_time = ls2x_rtc_set_time,
>> +};
>> +
>> +static int ls2x_rtc_probe(struct platform_device *pdev)
>> +{
>> +    struct device *dev = &pdev->dev;
>> +    struct rtc_device *rtc;
>> +    struct ls2x_rtc_priv *priv;
>> +    void __iomem *regs;
>> +    int ret;
>> +
>> +    priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +    if (unlikely(!priv))
>> +        return -ENOMEM;
>> +
>> +    spin_lock_init(&priv->lock);
>> +    platform_set_drvdata(pdev, priv);
>> +
>> +    regs = devm_platform_ioremap_resource(pdev, 0);
>> +    if (IS_ERR(regs)) {
>> +        ret = PTR_ERR(regs);
>> +        dev_err(dev, "Failed to map rtc registers: %d\n", ret);
>> +        return ret;
>> +    }
>> +
>> +    priv->regmap = devm_regmap_init_mmio(dev, regs,
>> +                         &ls2x_rtc_regmap_config);
>> +    if (IS_ERR(priv->regmap)) {
>> +        ret = PTR_ERR(priv->regmap);
>> +        dev_err(dev, "Failed to init regmap: %d\n", ret);
>> +        return ret;
>> +    }
>> +
>> +    rtc = devm_rtc_allocate_device(dev);
>> +    if (IS_ERR(rtc)) {
>> +        ret = PTR_ERR(rtc);
>> +        dev_err(dev, "Failed to allocate rtc device: %d\n", ret);
>> +        return ret;
>> +    }
>> +
>> +    rtc->ops = &ls2x_rtc_ops;
>> +
>> +    /* Due to hardware erratum, all years multiple of 4 are considered
>> +     * leap year, so only years 2000 through 2099 are usable.
>> +     *
>> +     * Previous out-of-tree versions of this driver wrote tm_year
>> directly
>> +     * into the year register, so epoch 2000 must be used to preserve
>> +     * semantics on shipped systems.
>> +     */
>> +    rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
>> +    rtc->range_max = RTC_TIMESTAMP_END_2099;
>> +
>> +    return rtc_register_device(rtc);
>> +}
>> +
>> +static const struct of_device_id ls2x_rtc_of_match[] = {
>> +    { .compatible = "loongson,ls2x-rtc" },
>> +    { /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, ls2x_rtc_of_match);
>> +
>> +static struct platform_driver ls2x_rtc_driver = {
>> +    .probe        = ls2x_rtc_probe,
>> +    .driver        = {
>> +        .name    = "ls2x-rtc",
>> +        .of_match_table = of_match_ptr(ls2x_rtc_of_match),
>> +    },
>> +};
>> +
>> +module_platform_driver(ls2x_rtc_driver);
>> +
>> +MODULE_DESCRIPTION("LS2X RTC driver");
>> +MODULE_AUTHOR("WANG Xuerui");
>> +MODULE_AUTHOR("Huacai Chen");
>> +MODULE_LICENSE("GPL");
>> +MODULE_ALIAS("platform:ls2x-rtc");
>