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[2403:580a:80ed:0:4835:5a07:49e7:f115]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2984dca0f28sm27386695ad.60.2025.11.12.03.17.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Nov 2025 03:17:57 -0800 (PST) From: James Calligeros Date: Wed, 12 Nov 2025 21:16:49 +1000 Subject: [PATCH v5 03/11] rtc: Add new rtc-macsmc driver for Apple Silicon Macs Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251112-macsmc-subdevs-v5-3-728e4b91fe81@gmail.com> References: <20251112-macsmc-subdevs-v5-0-728e4b91fe81@gmail.com> In-Reply-To: <20251112-macsmc-subdevs-v5-0-728e4b91fe81@gmail.com> To: Sven Peter , Janne Grunau , Alyssa Rosenzweig , Neal Gompa , Lee Jones , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Alexandre Belloni , Jean Delvare , Guenter Roeck , Dmitry Torokhov , Jonathan Corbet , James Calligeros Cc: asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rtc@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-input@vger.kernel.org, linux-doc@vger.kernel.org, Hector Martin X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=6867; i=jcalligeros99@gmail.com; h=from:subject:message-id; bh=JF8fPy7WCsEZI5w3lDmHu7AY077U0hzX/PAUVsnziAI=; b=owGbwMvMwCV2xczoYuD3ygTG02pJDJkiOUf6qjfx3bX13OPaHsl+9DJf7Lzzk/oXr7fZLMzOb NYwUc29YyILgxgXg6WYIsuGJiGP2UZsN/tFKvfCzGFlAhkiLdLAAAQsDHy5iXmlRjpGeqbahnqG hjrGOkYMXJwCMNVdWowMj+7kn+laYi7w7Os5xW+iLOfM5H6bTDkfdWOC0Jaqr1lWKgz/nXuEVoS 61E0rScoO/8J7/9gH21UH7qmf1FLL5jU/M6uJHwA= X-Developer-Key: i=jcalligeros99@gmail.com; a=openpgp; fpr=B08212489B3206D98F1479BDD43632D151F77960 From: Hector Martin Apple Silicon Macs (M1, etc.) have an RTC that is part of the PMU IC, but most of the PMU functionality is abstracted out by the SMC. On T600x machines, the RTC counter must be accessed via the SMC to get full functionality, and it seems likely that future machines will move towards making SMC handle all RTC functionality. The SMC RTC counter access is implemented on all current machines as of the time of this writing, on firmware 12.x. However, the RTC offset (needed to set the time) is still only accessible via direct PMU access. To handle this, we expose the RTC offset as an NVMEM cell from the SPMI PMU device node, and this driver consumes that cell and uses it to compute/set the current time. Reviewed-by: Neal Gompa Signed-off-by: Hector Martin Signed-off-by: Sven Peter Signed-off-by: James Calligeros --- MAINTAINERS | 1 + drivers/rtc/Kconfig | 11 ++ drivers/rtc/Makefile | 1 + drivers/rtc/rtc-macsmc.c | 140 +++++++++++++++++++++++++ 4 files changed, 153 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index 6e5e219c5fe6..5cf253a25831 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2464,6 +2464,7 @@ F: drivers/nvmem/apple-spmi-nvmem.c F: drivers/pinctrl/pinctrl-apple-gpio.c F: drivers/power/reset/macsmc-reboot.c F: drivers/pwm/pwm-apple.c +F: drivers/rtc/rtc-macsmc.c F: drivers/soc/apple/* F: drivers/spi/spi-apple.c F: drivers/spmi/spmi-apple-controller.c diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index 2933c41c77c8..cf3fa1475ffd 100644 --- a/drivers/rtc/Kconfig +++ b/drivers/rtc/Kconfig @@ -2074,6 +2074,17 @@ config RTC_DRV_WILCO_EC This can also be built as a module. If so, the module will be named "rtc_wilco_ec". +config RTC_DRV_MACSMC + tristate "Apple Mac System Management Controller RTC" + depends on MFD_MACSMC + help + If you say yes here you get support for RTC functions + inside Apple SPMI PMUs accessed through the SoC's + System Management Controller + + To compile this driver as a module, choose M here: the + module will be called rtc-macsmc. + config RTC_DRV_MSC313 tristate "MStar MSC313 RTC" depends on ARCH_MSTARV7 || COMPILE_TEST diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile index 8221bda6e6dc..0485b09caceb 100644 --- a/drivers/rtc/Makefile +++ b/drivers/rtc/Makefile @@ -93,6 +93,7 @@ obj-$(CONFIG_RTC_DRV_M48T35) += rtc-m48t35.o obj-$(CONFIG_RTC_DRV_M48T59) += rtc-m48t59.o obj-$(CONFIG_RTC_DRV_M48T86) += rtc-m48t86.o obj-$(CONFIG_RTC_DRV_MA35D1) += rtc-ma35d1.o +obj-$(CONFIG_RTC_DRV_MACSMC) += rtc-macsmc.o obj-$(CONFIG_RTC_DRV_MAX31335) += rtc-max31335.o obj-$(CONFIG_RTC_DRV_MAX6900) += rtc-max6900.o obj-$(CONFIG_RTC_DRV_MAX6902) += rtc-max6902.o diff --git a/drivers/rtc/rtc-macsmc.c b/drivers/rtc/rtc-macsmc.c new file mode 100644 index 000000000000..8fe883066956 --- /dev/null +++ b/drivers/rtc/rtc-macsmc.c @@ -0,0 +1,140 @@ +// SPDX-License-Identifier: GPL-2.0-only OR MIT +/* + * Apple SMC RTC driver + * Copyright The Asahi Linux Contributors + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +/* 48-bit RTC */ +#define RTC_BYTES 6 +#define RTC_BITS (8 * RTC_BYTES) + +/* 32768 Hz clock */ +#define RTC_SEC_SHIFT 15 + +struct macsmc_rtc { + struct device *dev; + struct apple_smc *smc; + struct rtc_device *rtc_dev; + struct nvmem_cell *rtc_offset; +}; + +static int macsmc_rtc_get_time(struct device *dev, struct rtc_time *tm) +{ + struct macsmc_rtc *rtc = dev_get_drvdata(dev); + u64 ctr = 0, off = 0; + time64_t now; + void *p_off; + size_t len; + int ret; + + ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES); + if (ret < 0) + return ret; + if (ret != RTC_BYTES) + return -EIO; + + p_off = nvmem_cell_read(rtc->rtc_offset, &len); + if (IS_ERR(p_off)) + return PTR_ERR(p_off); + if (len < RTC_BYTES) { + kfree(p_off); + return -EIO; + } + + memcpy(&off, p_off, RTC_BYTES); + kfree(p_off); + + /* Sign extend from 48 to 64 bits, then arithmetic shift right 15 bits to get seconds */ + now = sign_extend64(ctr + off, RTC_BITS - 1) >> RTC_SEC_SHIFT; + rtc_time64_to_tm(now, tm); + + return ret; +} + +static int macsmc_rtc_set_time(struct device *dev, struct rtc_time *tm) +{ + struct macsmc_rtc *rtc = dev_get_drvdata(dev); + u64 ctr = 0, off = 0; + int ret; + + ret = apple_smc_read(rtc->smc, SMC_KEY(CLKM), &ctr, RTC_BYTES); + if (ret < 0) + return ret; + if (ret != RTC_BYTES) + return -EIO; + + /* This sets the offset such that the set second begins now */ + off = (rtc_tm_to_time64(tm) << RTC_SEC_SHIFT) - ctr; + return nvmem_cell_write(rtc->rtc_offset, &off, RTC_BYTES); +} + +static const struct rtc_class_ops macsmc_rtc_ops = { + .read_time = macsmc_rtc_get_time, + .set_time = macsmc_rtc_set_time, +}; + +static int macsmc_rtc_probe(struct platform_device *pdev) +{ + struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent); + struct macsmc_rtc *rtc; + + /* + * MFD will probe this device even without a node in the device tree, + * thus bail out early if the SMC on the current machines does not + * support RTC and has no node in the device tree. + */ + if (!pdev->dev.of_node) + return -ENODEV; + + rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL); + if (!rtc) + return -ENOMEM; + + rtc->dev = &pdev->dev; + rtc->smc = smc; + + rtc->rtc_offset = devm_nvmem_cell_get(&pdev->dev, "rtc_offset"); + if (IS_ERR(rtc->rtc_offset)) + return dev_err_probe(&pdev->dev, PTR_ERR(rtc->rtc_offset), + "Failed to get rtc_offset NVMEM cell\n"); + + rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(rtc->rtc_dev)) + return PTR_ERR(rtc->rtc_dev); + + rtc->rtc_dev->ops = &macsmc_rtc_ops; + rtc->rtc_dev->range_min = S64_MIN >> (RTC_SEC_SHIFT + (64 - RTC_BITS)); + rtc->rtc_dev->range_max = S64_MAX >> (RTC_SEC_SHIFT + (64 - RTC_BITS)); + + platform_set_drvdata(pdev, rtc); + + return devm_rtc_register_device(rtc->rtc_dev); +} + +static const struct of_device_id macsmc_rtc_of_table[] = { + { .compatible = "apple,smc-rtc", }, + {} +}; +MODULE_DEVICE_TABLE(of, macsmc_rtc_of_table); + +static struct platform_driver macsmc_rtc_driver = { + .driver = { + .name = "macsmc-rtc", + .of_match_table = macsmc_rtc_of_table, + }, + .probe = macsmc_rtc_probe, +}; +module_platform_driver(macsmc_rtc_driver); + +MODULE_LICENSE("Dual MIT/GPL"); +MODULE_DESCRIPTION("Apple SMC RTC driver"); +MODULE_AUTHOR("Hector Martin "); -- 2.51.2