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Date: Thu, 10 May 2018 23:59:46 +0200
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc: a.zummo@...ertech.it, robh+dt@...nel.org, mark.rutland@....com,
linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] rtc: ds1307: add offset sysfs for mt41txx chips.
On 09/05/2018 21:33:54+0200, Giulio Benetti wrote:
> m41txx chips can hold a calibration value to get correct clock bias.
> If positive offset is passed, it means adding 512 cycles(@32.768Hz)
> every tick(1s).
> If negative offset is passed, it means subtracting 256 cycles(@32.768Hz)
> every tick(1s).
>
> Add offset handling (ranging between (-31) and 31) via sysfs.
>
> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> ---
> drivers/rtc/rtc-ds1307.c | 70 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 70 insertions(+)
>
> diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
> index 0ab0c166da83..33895668b363 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -114,6 +114,16 @@ enum ds_type {
> # define RX8025_BIT_VDET 0x40
> # define RX8025_BIT_XST 0x20
>
> +#define M41TXX_REG_CONTROL 0x07
> +# define M41TXX_BIT_OUT 0x80
> +# define M41TXX_BIT_FT 0x40
> +# define M41TXX_BIT_CALIB_SIGN 0x20
> +# define M41TXX_M_CALIBRATION 0x1f
> +
> +/* Min and max values supported with 'offset' interface by M41TXX */
> +#define M41TXX_MIN_OFFSET (-31)
> +#define M41TXX_MAX_OFFSET (31)
> +
> struct ds1307 {
> enum ds_type type;
> unsigned long flags;
> @@ -146,6 +156,9 @@ struct chip_desc {
>
> static int ds1307_get_time(struct device *dev, struct rtc_time *t);
> static int ds1307_set_time(struct device *dev, struct rtc_time *t);
> +static int ds1337_read_alarm(struct device *dev, struct rtc_wkalrm *t);
> +static int ds1337_set_alarm(struct device *dev, struct rtc_wkalrm *t);
> +static int ds1307_alarm_irq_enable(struct device *dev, unsigned int enabled);
> static u8 do_trickle_setup_ds1339(struct ds1307 *, u32 ohms, bool diode);
> static irqreturn_t rx8130_irq(int irq, void *dev_id);
> static int rx8130_read_alarm(struct device *dev, struct rtc_wkalrm *t);
> @@ -155,6 +168,8 @@ static irqreturn_t mcp794xx_irq(int irq, void *dev_id);
> static int mcp794xx_read_alarm(struct device *dev, struct rtc_wkalrm *t);
> static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t);
> static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled);
> +static int m41txx_rtc_read_offset(struct device *dev, long *offset);
> +static int m41txx_rtc_set_offset(struct device *dev, long offset);
>
> static const struct rtc_class_ops rx8130_rtc_ops = {
> .read_time = ds1307_get_time,
> @@ -172,6 +187,16 @@ static const struct rtc_class_ops mcp794xx_rtc_ops = {
> .alarm_irq_enable = mcp794xx_alarm_irq_enable,
> };
>
> +static const struct rtc_class_ops m41txx_rtc_ops = {
> + .read_time = ds1307_get_time,
> + .set_time = ds1307_set_time,
> + .read_alarm = ds1337_read_alarm,
> + .set_alarm = ds1337_set_alarm,
> + .alarm_irq_enable = ds1307_alarm_irq_enable,
> + .read_offset = m41txx_rtc_read_offset,
> + .set_offset = m41txx_rtc_set_offset,
> +};
> +
> static const struct chip_desc chips[last_ds_type] = {
> [ds_1307] = {
> .nvram_offset = 8,
> @@ -227,10 +252,17 @@ static const struct chip_desc chips[last_ds_type] = {
> .irq_handler = rx8130_irq,
> .rtc_ops = &rx8130_rtc_ops,
> },
> + [m41t0] = {
> + .rtc_ops = &m41txx_rtc_ops,
> + },
> + [m41t00] = {
> + .rtc_ops = &m41txx_rtc_ops,
> + },
> [m41t11] = {
> /* this is battery backed SRAM */
> .nvram_offset = 8,
> .nvram_size = 56,
> + .rtc_ops = &m41txx_rtc_ops,
> },
> [mcp794xx] = {
> .alarm = 1,
> @@ -972,6 +1004,44 @@ static int mcp794xx_alarm_irq_enable(struct device *dev, unsigned int enabled)
> enabled ? MCP794XX_BIT_ALM0_EN : 0);
> }
>
> +static int m41txx_rtc_read_offset(struct device *dev, long *offset)
> +{
> + struct ds1307 *ds1307 = dev_get_drvdata(dev);
> + unsigned int ctrl_reg;
> + u8 val;
> +
> + regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
> +
> + val = ctrl_reg & M41TXX_M_CALIBRATION;
> +
> + /* check if positive */
> + if (ctrl_reg & M41TXX_BIT_CALIB_SIGN)
> + *offset = val;
> + else
> + *offset = -val;
> +
This is definitively not right, you have to convert to/from ppb when
reading/setting the offset. The datasheet gives you the correct steps in
ppm.
> + return 0;
> +}
> +
> +static int m41txx_rtc_set_offset(struct device *dev, long offset)
> +{
> + struct ds1307 *ds1307 = dev_get_drvdata(dev);
> + unsigned int ctrl_reg;
> +
> + if ((offset < M41TXX_MIN_OFFSET) || (offset > M41TXX_MAX_OFFSET))
> + return -ERANGE;
> +
> + regmap_read(ds1307->regmap, M41TXX_REG_CONTROL, &ctrl_reg);
> +
> + ctrl_reg &= ~M41TXX_M_CALIBRATION;
> + ctrl_reg |= abs(offset) & M41TXX_M_CALIBRATION;
> +
> + if (offset >= 0)
> + ctrl_reg |= M41TXX_BIT_CALIB_SIGN;
> +
> + return regmap_write(ds1307->regmap, M41TXX_REG_CONTROL, ctrl_reg);
Please use regmap_update_bits
> +}
> +
> /*----------------------------------------------------------------------*/
>
> static int ds1307_nvram_read(void *priv, unsigned int offset, void *val,
> --
> 2.17.0
>
--
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
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