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Message-ID: <YdTcuX9q+m+GRLdk@piout.net>
Date: Wed, 5 Jan 2022 00:48:09 +0100
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: Srinivas Neeli <srinivas.neeli@...inx.com>
Cc: a.zummo@...ertech.it, michal.simek@...inx.com, sgoud@...inx.com,
shubhraj@...inx.com, radheys@...inx.com, linux-rtc@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
git@...inx.com
Subject: Re: [PATCH V3 2/2] rtc: zynqmp: Add calibration set and get support
On 30/11/2021 11:25:41+0530, Srinivas Neeli wrote:
> Zynqmp RTC controller has a calibration feature to compensate
> time deviation due to input clock inaccuracy.
> Set and get calibration API's are used for setting and getting
> calibration value from the controller calibration register.
>
> Signed-off-by: Srinivas Neeli <srinivas.neeli@...inx.com>
> ---
> Changes in V3:
> -Calculated tick_mult using crystal frequency.
> -Calibration register updating based on crystal frequency in probe.
> -Supressed MIN an MAX calibration values,Will send separate patch in future.
I believe this should go in with this patch and it shouldn't be too
complicated to know whether the calculated value overflows the register.
> Changes in V2:
> -Removed unused macro.
> -Updated code with review comments.
> ---
> drivers/rtc/rtc-zynqmp.c | 104 +++++++++++++++++++++++++++++++--------
> 1 file changed, 84 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
> index f440bb52be92..eb6ee55ca725 100644
> --- a/drivers/rtc/rtc-zynqmp.c
> +++ b/drivers/rtc/rtc-zynqmp.c
> @@ -6,6 +6,7 @@
> *
> */
>
> +#include <linux/clk.h>
> #include <linux/delay.h>
> #include <linux/init.h>
> #include <linux/io.h>
> @@ -36,17 +37,21 @@
> #define RTC_OSC_EN BIT(24)
> #define RTC_BATT_EN BIT(31)
>
> -#define RTC_CALIB_DEF 0x198233
> +#define RTC_CALIB_DEF 0x8000
> #define RTC_CALIB_MASK 0x1FFFFF
> #define RTC_ALRM_MASK BIT(1)
> #define RTC_MSEC 1000
> +#define RTC_FR_MASK 0xF0000
> +#define RTC_FR_MAX_TICKS 16
> +#define RTC_PPB 1000000000LL
>
> struct xlnx_rtc_dev {
> struct rtc_device *rtc;
> void __iomem *reg_base;
> int alarm_irq;
> int sec_irq;
> - unsigned int calibval;
> + struct clk *rtc_clk;
> + unsigned int freq;
> };
>
> static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
> @@ -61,13 +66,6 @@ static int xlnx_rtc_set_time(struct device *dev, struct rtc_time *tm)
> */
> new_time = rtc_tm_to_time64(tm) + 1;
>
> - /*
> - * Writing into calibration register will clear the Tick Counter and
> - * force the next second to be signaled exactly in 1 second period
> - */
> - xrtcdev->calibval &= RTC_CALIB_MASK;
> - writel(xrtcdev->calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
> -
> writel(new_time, xrtcdev->reg_base + RTC_SET_TM_WR);
>
> /*
> @@ -173,15 +171,71 @@ static void xlnx_init_rtc(struct xlnx_rtc_dev *xrtcdev)
> rtc_ctrl = readl(xrtcdev->reg_base + RTC_CTRL);
> rtc_ctrl |= RTC_BATT_EN;
> writel(rtc_ctrl, xrtcdev->reg_base + RTC_CTRL);
> +}
>
> - /*
> - * Based on crystal freq of 33.330 KHz
> - * set the seconds counter and enable, set fractions counter
> - * to default value suggested as per design spec
> - * to correct RTC delay in frequency over period of time.
> +static int xlnx_rtc_read_offset(struct device *dev, long *offset)
> +{
> + struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
> + long offset_val = 0;
> + unsigned int tick_mult = RTC_PPB / xrtcdev->freq;
> + unsigned int calibval;
> +
> + calibval = readl(xrtcdev->reg_base + RTC_CALIB_RD);
> + /* Offset with seconds ticks */
> + offset_val = calibval & RTC_TICK_MASK;
> + offset_val = offset_val - RTC_CALIB_DEF;
> + offset_val = offset_val * tick_mult;
> +
> + /* Offset with fractional ticks */
> + if (calibval & RTC_FR_EN)
> + offset_val += ((calibval & RTC_FR_MASK) >> RTC_FR_DATSHIFT)
> + * (tick_mult / RTC_FR_MAX_TICKS);
> + *offset = offset_val;
> +
> + return 0;
> +}
> +
> +static int xlnx_rtc_set_offset(struct device *dev, long offset)
> +{
> + struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
> + short int max_tick;
> + unsigned char fract_tick = 0;
> + unsigned int calibval;
> + int fract_offset;
> + unsigned int tick_mult = RTC_PPB / xrtcdev->freq;
> +
> + /* Number ticks for given offset */
> + max_tick = div_s64_rem(offset, tick_mult, &fract_offset);
> +
> + /* Number fractional ticks for given offset */
> + if (fract_offset) {
> + if (fract_offset < 0) {
> + fract_offset = fract_offset + tick_mult;
> + max_tick--;
> + }
> + if (fract_offset > (tick_mult / RTC_FR_MAX_TICKS)) {
> + for (fract_tick = 1; fract_tick < 16; fract_tick++) {
> + if (fract_offset <=
> + (fract_tick *
> + (tick_mult / RTC_FR_MAX_TICKS)))
> + break;
> + }
> + }
> + }
> +
> + /* Zynqmp RTC uses second and fractional tick
> + * counters for compensation
> */
> - xrtcdev->calibval &= RTC_CALIB_MASK;
> - writel(xrtcdev->calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
> + calibval = max_tick + RTC_CALIB_DEF;
> +
> + if (fract_tick)
> + calibval |= RTC_FR_EN;
> +
> + calibval |= (fract_tick << RTC_FR_DATSHIFT);
> +
> + writel(calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
> +
> + return 0;
> }
>
> static const struct rtc_class_ops xlnx_rtc_ops = {
> @@ -190,6 +244,8 @@ static const struct rtc_class_ops xlnx_rtc_ops = {
> .read_alarm = xlnx_rtc_read_alarm,
> .set_alarm = xlnx_rtc_set_alarm,
> .alarm_irq_enable = xlnx_rtc_alarm_irq_enable,
> + .read_offset = xlnx_rtc_read_offset,
> + .set_offset = xlnx_rtc_set_offset,
> };
>
> static irqreturn_t xlnx_rtc_interrupt(int irq, void *id)
> @@ -255,10 +311,18 @@ static int xlnx_rtc_probe(struct platform_device *pdev)
> return ret;
> }
>
> - ret = of_property_read_u32(pdev->dev.of_node, "calibration",
> - &xrtcdev->calibval);
> - if (ret)
> - xrtcdev->calibval = RTC_CALIB_DEF;
> + /* Getting the rtc_clk info */
> + xrtcdev->rtc_clk = devm_clk_get_optional(&pdev->dev, "rtc_clk");
> + if (IS_ERR(xrtcdev->rtc_clk)) {
> + if (PTR_ERR(xrtcdev->rtc_clk) != -EPROBE_DEFER)
> + dev_warn(&pdev->dev, "Device clock not found.\n");
> + }
> + xrtcdev->freq = clk_get_rate(xrtcdev->rtc_clk);
> + if (!xrtcdev->freq)
> + xrtcdev->freq = RTC_CALIB_DEF;
Because you changed the value of RTC_CALIB_DEF, I think this breaks
existing DTs.
> + ret = readl(xrtcdev->reg_base + RTC_CALIB_RD);
> + if (!ret)
> + writel(xrtcdev->freq, (xrtcdev->reg_base + RTC_CALIB_WR));
>
> xlnx_init_rtc(xrtcdev);
>
> --
> 2.17.1
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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