330 lines
6.5 KiB
C
330 lines
6.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Holtek HT1380/HT1381 Serial Timekeeper Chip
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*
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* Communication with the chip is vendor-specific.
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* It is done via 3 GPIO pins: reset, clock, and data.
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* Describe in .dts this way:
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*
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* rtc {
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* compatible = "holtek,ht1380";
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* rst-gpios = <&gpio 19 GPIO_ACTIVE_LOW>;
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* clk-gpios = <&gpio 20 GPIO_ACTIVE_HIGH>;
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* dat-gpios = <&gpio 21 GPIO_ACTIVE_HIGH>;
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* };
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*
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*/
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#include <common.h>
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#include <dm.h>
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#include <rtc.h>
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#include <bcd.h>
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#include <asm/gpio.h>
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#include <linux/delay.h>
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struct ht1380_priv {
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struct gpio_desc rst_desc;
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struct gpio_desc clk_desc;
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struct gpio_desc dat_desc;
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};
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enum registers {
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SEC,
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MIN,
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HOUR,
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MDAY,
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MONTH,
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WDAY,
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YEAR,
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WP,
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N_REGS
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};
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enum hour_mode {
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AMPM_MODE = 0x80, /* RTC is in AM/PM mode */
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PM_NOW = 0x20, /* set if PM, clear if AM */
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};
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static const int BURST = 0xbe;
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static const int READ = 1;
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static void ht1380_half_period_delay(void)
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{
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/*
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* Delay for half a period. 1 us complies with the 500 KHz maximum
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* input serial clock limit given by the datasheet.
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*/
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udelay(1);
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}
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static int ht1380_send_byte(struct ht1380_priv *priv, int byte)
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{
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int ret;
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for (int bit = 0; bit < 8; bit++) {
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ret = dm_gpio_set_value(&priv->dat_desc, byte >> bit & 1);
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if (ret)
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break;
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ht1380_half_period_delay();
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ret = dm_gpio_set_value(&priv->clk_desc, 1);
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if (ret)
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break;
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ht1380_half_period_delay();
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ret = dm_gpio_set_value(&priv->clk_desc, 0);
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if (ret)
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break;
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}
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return ret;
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}
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/*
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* Leave reset state. The transfer operation can then be started.
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*/
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static int ht1380_reset_off(struct ht1380_priv *priv)
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{
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const unsigned int T_CC = 4; /* us, Reset to Clock Setup */
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int ret;
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/*
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* Leave RESET state.
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* Make sure we make the minimal delay required by the datasheet.
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*/
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ret = dm_gpio_set_value(&priv->rst_desc, 0);
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udelay(T_CC);
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return ret;
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}
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/*
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* Enter reset state. Completes the transfer operation.
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*/
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static int ht1380_reset_on(struct ht1380_priv *priv)
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{
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const unsigned int T_CWH = 4; /* us, Reset Inactive Time */
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int ret;
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/*
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* Enter RESET state.
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* Make sure we make the minimal delay required by the datasheet.
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*/
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ret = dm_gpio_set_value(&priv->rst_desc, 1);
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udelay(T_CWH);
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return ret;
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}
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static int ht1380_rtc_get(struct udevice *dev, struct rtc_time *tm)
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{
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struct ht1380_priv *priv = dev_get_priv(dev);
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int ret, i, bit, reg[N_REGS];
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ret = dm_gpio_set_value(&priv->clk_desc, 0);
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if (ret)
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return ret;
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ret = dm_gpio_set_dir_flags(&priv->dat_desc, GPIOD_IS_OUT);
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if (ret)
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return ret;
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ret = ht1380_reset_off(priv);
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if (ret)
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goto exit;
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ret = ht1380_send_byte(priv, BURST + READ);
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if (ret)
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goto exit;
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ret = dm_gpio_set_dir_flags(&priv->dat_desc, GPIOD_IS_IN);
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if (ret)
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goto exit;
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for (i = 0; i < N_REGS; i++) {
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reg[i] = 0;
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for (bit = 0; bit < 8; bit++) {
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ht1380_half_period_delay();
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ret = dm_gpio_set_value(&priv->clk_desc, 1);
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if (ret)
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goto exit;
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ht1380_half_period_delay();
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reg[i] |= dm_gpio_get_value(&priv->dat_desc) << bit;
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ret = dm_gpio_set_value(&priv->clk_desc, 0);
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if (ret)
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goto exit;
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}
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}
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ret = -EINVAL;
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/* Correctness check: some bits are always zero */
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if (reg[MIN] & 0x80 || reg[HOUR] & 0x40 || reg[MDAY] & 0xc0 ||
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reg[MONTH] & 0xe0 || reg[WDAY] & 0xf8 || reg[WP] & 0x7f)
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goto exit;
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/* Correctness check: some registers are always non-zero */
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if (!reg[MDAY] || !reg[MONTH] || !reg[WDAY])
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goto exit;
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tm->tm_sec = bcd2bin(reg[SEC]);
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tm->tm_min = bcd2bin(reg[MIN]);
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if (reg[HOUR] & AMPM_MODE) {
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/* AM-PM Mode, range is 01-12 */
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tm->tm_hour = bcd2bin(reg[HOUR] & 0x1f) % 12;
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if (reg[HOUR] & PM_NOW) {
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/* it is PM (otherwise AM) */
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tm->tm_hour += 12;
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}
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} else {
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/* 24-hour Mode, range is 0-23 */
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tm->tm_hour = bcd2bin(reg[HOUR]);
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}
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tm->tm_mday = bcd2bin(reg[MDAY]);
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tm->tm_mon = bcd2bin(reg[MONTH]);
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tm->tm_year = 2000 + bcd2bin(reg[YEAR]);
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tm->tm_wday = bcd2bin(reg[WDAY]) - 1;
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tm->tm_yday = 0;
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tm->tm_isdst = 0;
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ret = 0;
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exit:
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ht1380_reset_on(priv);
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return ret;
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}
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static int ht1380_write_protection_off(struct ht1380_priv *priv)
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{
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int ret;
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const int PROTECT = 0x8e;
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ret = ht1380_reset_off(priv);
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if (ret)
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return ret;
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ret = ht1380_send_byte(priv, PROTECT);
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if (ret)
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return ret;
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ret = ht1380_send_byte(priv, 0); /* WP bit is 0 */
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if (ret)
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return ret;
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return ht1380_reset_on(priv);
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}
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static int ht1380_rtc_set(struct udevice *dev, const struct rtc_time *tm)
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{
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struct ht1380_priv *priv = dev_get_priv(dev);
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int ret, i, reg[N_REGS];
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ret = dm_gpio_set_value(&priv->clk_desc, 0);
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if (ret)
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return ret;
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ret = dm_gpio_set_dir_flags(&priv->dat_desc, GPIOD_IS_OUT);
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if (ret)
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goto exit;
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ret = ht1380_write_protection_off(priv);
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if (ret)
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goto exit;
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reg[SEC] = bin2bcd(tm->tm_sec);
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reg[MIN] = bin2bcd(tm->tm_min);
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reg[HOUR] = bin2bcd(tm->tm_hour);
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reg[MDAY] = bin2bcd(tm->tm_mday);
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reg[MONTH] = bin2bcd(tm->tm_mon);
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reg[WDAY] = bin2bcd(tm->tm_wday) + 1;
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reg[YEAR] = bin2bcd(tm->tm_year - 2000);
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reg[WP] = 0x80; /* WP bit is 1 */
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ret = ht1380_reset_off(priv);
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if (ret)
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goto exit;
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ret = ht1380_send_byte(priv, BURST);
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for (i = 0; i < N_REGS && ret; i++)
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ret = ht1380_send_byte(priv, reg[i]);
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exit:
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ht1380_reset_on(priv);
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return ret;
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}
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static int ht1380_probe(struct udevice *dev)
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{
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int ret;
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struct ht1380_priv *priv;
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priv = dev_get_priv(dev);
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if (!priv)
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return -EINVAL;
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ret = gpio_request_by_name(dev, "rst-gpios", 0,
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&priv->rst_desc, GPIOD_IS_OUT);
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if (ret)
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goto fail_rst;
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ret = gpio_request_by_name(dev, "clk-gpios", 0,
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&priv->clk_desc, GPIOD_IS_OUT);
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if (ret)
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goto fail_clk;
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ret = gpio_request_by_name(dev, "dat-gpios", 0,
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&priv->dat_desc, 0);
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if (ret)
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goto fail_dat;
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ret = ht1380_reset_on(priv);
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if (ret)
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goto fail;
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return 0;
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fail:
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dm_gpio_free(dev, &priv->dat_desc);
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fail_dat:
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dm_gpio_free(dev, &priv->clk_desc);
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fail_clk:
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dm_gpio_free(dev, &priv->rst_desc);
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fail_rst:
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return ret;
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}
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static int ht1380_remove(struct udevice *dev)
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{
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struct ht1380_priv *priv = dev_get_priv(dev);
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dm_gpio_free(dev, &priv->rst_desc);
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dm_gpio_free(dev, &priv->clk_desc);
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dm_gpio_free(dev, &priv->dat_desc);
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return 0;
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}
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static const struct rtc_ops ht1380_rtc_ops = {
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.get = ht1380_rtc_get,
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.set = ht1380_rtc_set,
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};
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static const struct udevice_id ht1380_rtc_ids[] = {
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{ .compatible = "holtek,ht1380" },
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{ }
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};
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U_BOOT_DRIVER(rtc_ht1380) = {
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.name = "rtc-ht1380",
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.id = UCLASS_RTC,
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.probe = ht1380_probe,
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.remove = ht1380_remove,
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.of_match = ht1380_rtc_ids,
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.ops = &ht1380_rtc_ops,
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.priv_auto = sizeof(struct ht1380_priv),
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};
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