^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) // SPDX-License-Identifier: GPL-2.0+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) * rtc-dm355evm.c - access battery-backed counter in MSP430 firmware
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) * Copyright (c) 2008 by David Brownell
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) #include <linux/kernel.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) #include <linux/init.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) #include <linux/rtc.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) #include <linux/platform_device.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) #include <linux/mfd/dm355evm_msp.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) #include <linux/module.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) * The MSP430 firmware on the DM355 EVM uses a watch crystal to feed
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) * a 1 Hz counter. When a backup battery is supplied, that makes a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) * reasonable RTC for applications where alarms and non-NTP drift
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) * compensation aren't important.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) * The only real glitch is the inability to read or write all four
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) * counter bytes atomically: the count may increment in the middle
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) * of an operation, causing trouble when the LSB rolls over.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) * This driver was tested with firmware revision A4.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) union evm_time {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) u8 bytes[4];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) u32 value;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) static int dm355evm_rtc_read_time(struct device *dev, struct rtc_time *tm)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) union evm_time time;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) int status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) int tries = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) * Read LSB(0) to MSB(3) bytes. Defend against the counter
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) * rolling over by re-reading until the value is stable,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) * and assuming the four reads take at most a few seconds.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) status = dm355evm_msp_read(DM355EVM_MSP_RTC_0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) if (tries && time.bytes[0] == status)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50) time.bytes[0] = status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) status = dm355evm_msp_read(DM355EVM_MSP_RTC_1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) if (tries && time.bytes[1] == status)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) time.bytes[1] = status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) status = dm355evm_msp_read(DM355EVM_MSP_RTC_2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) if (tries && time.bytes[2] == status)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) time.bytes[2] = status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) status = dm355evm_msp_read(DM355EVM_MSP_RTC_3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) if (tries && time.bytes[3] == status)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) break;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) time.bytes[3] = status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) } while (++tries < 5);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75) dev_dbg(dev, "read timestamp %08x\n", time.value);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) rtc_time64_to_tm(le32_to_cpu(time.value), tm);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) static int dm355evm_rtc_set_time(struct device *dev, struct rtc_time *tm)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) union evm_time time;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) unsigned long value;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) int status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) value = rtc_tm_to_time64(tm);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) time.value = cpu_to_le32(value);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) dev_dbg(dev, "write timestamp %08x\n", time.value);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) * REVISIT handle non-atomic writes ... maybe just retry until
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) * byte[1] sticks (no rollover)?
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) status = dm355evm_msp_write(time.bytes[0], DM355EVM_MSP_RTC_0);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) status = dm355evm_msp_write(time.bytes[1], DM355EVM_MSP_RTC_1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) status = dm355evm_msp_write(time.bytes[2], DM355EVM_MSP_RTC_2);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) status = dm355evm_msp_write(time.bytes[3], DM355EVM_MSP_RTC_3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) if (status < 0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) return status;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) static const struct rtc_class_ops dm355evm_rtc_ops = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) .read_time = dm355evm_rtc_read_time,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) .set_time = dm355evm_rtc_set_time,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) /*----------------------------------------------------------------------*/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) static int dm355evm_rtc_probe(struct platform_device *pdev)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) struct rtc_device *rtc;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) rtc = devm_rtc_allocate_device(&pdev->dev);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) if (IS_ERR(rtc))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) return PTR_ERR(rtc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) platform_set_drvdata(pdev, rtc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) rtc->ops = &dm355evm_rtc_ops;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) rtc->range_max = U32_MAX;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) return rtc_register_device(rtc);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) * I2C is used to talk to the MSP430, but this platform device is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) * exposed by an MFD driver that manages I2C communications.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) static struct platform_driver rtc_dm355evm_driver = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) .probe = dm355evm_rtc_probe,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) .driver = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) .name = "rtc-dm355evm",
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) },
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) module_platform_driver(rtc_dm355evm_driver);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) MODULE_LICENSE("GPL");
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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