Re: [PATCH 3/7] rtc: pm8xxx: add support for uefi offset

Tobias Heider
2025-01-24T12:57:03Z

On Mon, Jan 20, 2025 at 03:41:48PM GMT, Johan Hovold wrote:
> On many Qualcomm platforms the PMIC RTC control and time registers are
> read-only so that the RTC time can not be updated. Instead an offset
> needs be stored in some machine-specific non-volatile memory, which the
> driver can take into account.
>
> Add support for storing a 32-bit offset from the GPS time epoch in a
> UEFI variable so that the RTC time can be set on such platforms.
>
> The UEFI variable is
>
> 882f8c2b-9646-435f-8de5-f208ff80c1bd-RTCInfo
>
> and holds a 12-byte structure where the first four bytes is a GPS time
> offset in little-endian byte order.
>
> Note that this format is not arbitrary as the variable is shared with
> the UEFI firmware (and Windows).
>
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>

Thanks for the great work Johan, seems to work nicely here!

I think you might need to add MODULE_IMPORT_NS(EFIVAR) for the efivar_*
API calls you added.

> ---
> drivers/rtc/rtc-pm8xxx.c | 125 +++++++++++++++++++++++++++++++++++++--
> include/linux/rtc.h | 1 +
> 2 files changed, 121 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/rtc/rtc-pm8xxx.c b/drivers/rtc/rtc-pm8xxx.c
> index 2f32187ecc8d..be1983bf35cd 100644
> --- a/drivers/rtc/rtc-pm8xxx.c
> +++ b/drivers/rtc/rtc-pm8xxx.c
> @@ -5,6 +5,7 @@
> * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
> * Copyright (c) 2023, Linaro Limited
> */
> +#include <linux/efi.h>
> #include <linux/of.h>
> #include <linux/module.h>
> #include <linux/nvmem-consumer.h>
> @@ -16,9 +17,10 @@
> #include <linux/regmap.h>
> #include <linux/slab.h>
> #include <linux/spinlock.h>
> -
> #include <linux/unaligned.h>
>
> +#include <asm/byteorder.h>
> +
> /* RTC_CTRL register bit fields */
> #define PM8xxx_RTC_ENABLE BIT(7)
> #define PM8xxx_RTC_ALARM_CLEAR BIT(0)
> @@ -46,14 +48,21 @@ struct pm8xxx_rtc_regs {
> unsigned int alarm_en;
> };
>
> +struct qcom_uefi_rtc_info {
> + __le32 offset_gps;
> + u8 reserved[8];
> +} __packed;
> +
> /**
> * struct pm8xxx_rtc - RTC driver internal structure
> * @rtc: RTC device
> * @regmap: regmap used to access registers
> * @allow_set_time: whether the time can be set
> + * @use_uefi: use UEFI variable as fallback for offset
> * @alarm_irq: alarm irq number
> * @regs: register description
> * @dev: device structure
> + * @rtc_info: qcom uefi rtc-info structure
> * @nvmem_cell: nvmem cell for offset
> * @offset: offset from epoch in seconds
> */
> @@ -61,13 +70,101 @@ struct pm8xxx_rtc {
> struct rtc_device *rtc;
> struct regmap *regmap;
> bool allow_set_time;
> + bool use_uefi;
> int alarm_irq;
> const struct pm8xxx_rtc_regs *regs;
> struct device *dev;
> + struct qcom_uefi_rtc_info rtc_info;
> struct nvmem_cell *nvmem_cell;
> u32 offset;
> };
>
> +#ifdef CONFIG_EFI
> +
> +MODULE_IMPORT_NS("EFIVAR");
> +
> +#define QCOM_UEFI_NAME L"RTCInfo"
> +#define QCOM_UEFI_GUID EFI_GUID(0x882f8c2b, 0x9646, 0x435f, \
> + 0x8d, 0xe5, 0xf2, 0x08, 0xff, 0x80, 0xc1, 0xbd)
> +#define QCOM_UEFI_ATTRS (EFI_VARIABLE_NON_VOLATILE | \
> + EFI_VARIABLE_BOOTSERVICE_ACCESS | \
> + EFI_VARIABLE_RUNTIME_ACCESS)
> +
> +static int pm8xxx_rtc_read_uefi_offset(struct pm8xxx_rtc *rtc_dd)
> +{
> + struct qcom_uefi_rtc_info *rtc_info = &rtc_dd->rtc_info;
> + unsigned long size = sizeof(*rtc_info);
> + struct device *dev = rtc_dd->dev;
> + efi_status_t status;
> + u32 offset_gps;
> + int rc;
> +
> + rc = efivar_lock();
> + if (rc)
> + return rc;
> +
> + status = efivar_get_variable(QCOM_UEFI_NAME, &QCOM_UEFI_GUID, NULL,
> + &size, rtc_info);
> + efivar_unlock();
> +
> + if (status != EFI_SUCCESS) {
> + dev_dbg(dev, "failed to read UEFI offset: %lu\n", status);
> + return efi_status_to_err(status);
> + }
> +
> + if (size != sizeof(*rtc_info)) {
> + dev_dbg(dev, "unexpected UEFI structure size %lu\n", size);
> + return -EINVAL;
> + }
> +
> + dev_dbg(dev, "uefi_rtc_info = %*ph\n", (int)size, rtc_info);
> +
> + /* Convert from GPS to Unix time offset */
> + offset_gps = le32_to_cpu(rtc_info->offset_gps);
> + rtc_dd->offset = offset_gps + (u32)RTC_TIMESTAMP_EPOCH_GPS;
> +
> + return 0;
> +}
> +
> +static int pm8xxx_rtc_write_uefi_offset(struct pm8xxx_rtc *rtc_dd, u32 offset)
> +{
> + struct qcom_uefi_rtc_info *rtc_info = &rtc_dd->rtc_info;
> + unsigned long size = sizeof(*rtc_info);
> + struct device *dev = rtc_dd->dev;
> + efi_status_t status;
> + u32 offset_gps;
> +
> + /* Convert from Unix to GPS time offset */
> + offset_gps = offset - (u32)RTC_TIMESTAMP_EPOCH_GPS;
> +
> + rtc_info->offset_gps = cpu_to_le32(offset_gps);
> +
> + dev_dbg(dev, "efi_rtc_info = %*ph\n", (int)size, rtc_info);
> +
> + status = efivar_set_variable(QCOM_UEFI_NAME, &QCOM_UEFI_GUID,
> + QCOM_UEFI_ATTRS, size, rtc_info);
> + if (status != EFI_SUCCESS) {
> + dev_dbg(dev, "failed to write UEFI offset: %lx\n", status);
> + return efi_status_to_err(status);
> + }
> +
> + return 0;
> +}
> +
> +#else /* CONFIG_EFI */
> +
> +static int pm8xxx_rtc_read_uefi_offset(struct pm8xxx_rtc *rtc_dd)
> +{
> + return -ENODEV;
> +}
> +
> +static int pm8xxx_rtc_write_uefi_offset(struct pm8xxx_rtc *rtc_dd, u32 offset)
> +{
> + return -ENODEV;
> +}
> +
> +#endif /* CONFIG_EFI */
> +
> static int pm8xxx_rtc_read_nvmem_offset(struct pm8xxx_rtc *rtc_dd)
> {
> size_t len;
> @@ -112,10 +209,13 @@ static int pm8xxx_rtc_write_nvmem_offset(struct pm8xxx_rtc *rtc_dd, u32 offset)
>
> static int pm8xxx_rtc_read_offset(struct pm8xxx_rtc *rtc_dd)
> {
> - if (!rtc_dd->nvmem_cell)
> + if (!rtc_dd->nvmem_cell && !rtc_dd->use_uefi)
> return 0;
>
> - return pm8xxx_rtc_read_nvmem_offset(rtc_dd);
> + if (rtc_dd->nvmem_cell)
> + return pm8xxx_rtc_read_nvmem_offset(rtc_dd);
> + else
> + return pm8xxx_rtc_read_uefi_offset(rtc_dd);
> }
>
> static int pm8xxx_rtc_read_raw(struct pm8xxx_rtc *rtc_dd, u32 *secs)
> @@ -155,7 +255,7 @@ static int pm8xxx_rtc_update_offset(struct pm8xxx_rtc *rtc_dd, u32 secs)
> u32 offset;
> int rc;
>
> - if (!rtc_dd->nvmem_cell)
> + if (!rtc_dd->nvmem_cell && !rtc_dd->use_uefi)
> return -ENODEV;
>
> rc = pm8xxx_rtc_read_raw(rtc_dd, &raw_secs);
> @@ -167,7 +267,11 @@ static int pm8xxx_rtc_update_offset(struct pm8xxx_rtc *rtc_dd, u32 secs)
> if (offset == rtc_dd->offset)
> return 0;
>
> - rc = pm8xxx_rtc_write_nvmem_offset(rtc_dd, offset);
> + if (rtc_dd->nvmem_cell)
> + rc = pm8xxx_rtc_write_nvmem_offset(rtc_dd, offset);
> + else
> + rc = pm8xxx_rtc_write_uefi_offset(rtc_dd, offset);
> +
> if (rc)
> return rc;
>
> @@ -486,6 +590,17 @@ static int pm8xxx_rtc_probe(struct platform_device *pdev)
> if (rc != -ENOENT)
> return rc;
> rtc_dd->nvmem_cell = NULL;
> +
> + /* Use UEFI storage as fallback if available */
> + rtc_dd->use_uefi = of_property_read_bool(pdev->dev.of_node,
> + "qcom,uefi-rtc-info");
> + }
> +
> + if (rtc_dd->use_uefi && !efivar_is_available()) {
> + if (IS_ENABLED(CONFIG_EFI))
> + return -EPROBE_DEFER;
> + dev_warn(&pdev->dev, "efivars not available\n");
> + rtc_dd->use_uefi = false;
> }
>
> rtc_dd->regs = match->data;
> diff --git a/include/linux/rtc.h b/include/linux/rtc.h
> index 3f4d315aaec9..95da051fb155 100644
> --- a/include/linux/rtc.h
> +++ b/include/linux/rtc.h
> @@ -170,6 +170,7 @@ struct rtc_device {
> /* useful timestamps */
> #define RTC_TIMESTAMP_BEGIN_0000 -62167219200ULL /* 0000-01-01 00:00:00 */
> #define RTC_TIMESTAMP_BEGIN_1900 -2208988800LL /* 1900-01-01 00:00:00 */
> +#define RTC_TIMESTAMP_EPOCH_GPS 315964800LL /* 1980-01-06 00:00:00 */
> #define RTC_TIMESTAMP_BEGIN_2000 946684800LL /* 2000-01-01 00:00:00 */
> #define RTC_TIMESTAMP_END_2063 2966371199LL /* 2063-12-31 23:59:59 */
> #define RTC_TIMESTAMP_END_2079 3471292799LL /* 2079-12-31 23:59:59 */
> --
> 2.45.2
>
>