[PATCH v10 3/3] rtc: Add Raspberry Pi 5 RTC driver
Sander Speetjens
sander.speetjens at gmail.com
Fri Oct 2 08:02:16 PDT 2026
Hi stefan,
I was thinking of making the raspberrypi.c firmware a speparate patch,
what would you think of this?
Because it overlays with another patch
(https://lore.kernel.org/linux-arm-kernel/20260919034840.28593-2-triet.hoang.dev@gmail.com/)
Kind regards
On Fri, 2 Oct 2026 at 15:58, Stefan Wahren <wahrenst at gmx.net> wrote:
>
> Hello Sander,
>
> Am 02.10.26 um 12:24 schrieb Sander Speetjens:
> > Upstreaming the downstream Raspberry Pi 5 RTC driver.
> > This driver supports the custom DA9091,
> > which is accessed through the firmware mailbox.
> >
> > Based on code originally written by Jonathan Bell <jonathan at raspberrypi.com>
> > and Dom Cobley <popcornmix at gmail.com>
> >
> > Signed-off-by: Sander Speetjens <sander.speetjens at gmail.com>
> in general this patch looks good except a few nits, maybe wait for
> Alexandre's feedback.
> After fixing the nits you can add my:
>
> Reviewed-by: Stefan Wahren <wahrenst at gmx.net>
> > ---
> > V9 -> V10:
> > - Fix sign-off-by
> > - Change enum to defines
> > - Change comment in firmware
> >
> > V8 -> V9:
> > - Fix whitespace in Kconfig
> > - Move RTC regs to firmware header
> > - Add a warn when getting the min or max charging values fails
> > - Remove the unused return value of set charge voltage
> >
> > V7 -> V8:
> > - Fix whitespacing errors
> > - Use of_machine_is_compatible instead of strncmp
> >
> > V6 -> V7:
> > - Move from u32 array to struct
> > - Fix encapsulation as mentioned by sashiko-bot
> >
> > V5 -> V6:
> > - Add MODULE_ALIAS, as mentioned by sashiko-bot
> > - Encapsulate the mailbox data in le32_to_cpu or cpu_to_le32, as
> > mentioned by sashiko-bot. For good practice
> >
> > V4 -> V5: No changes
> >
> > V3 -> V4:
> > - Fix Kconfig depends that disallows having Raspberrypi
> > firmware built as a module while the rtc driver is built in
> > - Remove sysfs
> > - Add limits from firmware properties and check in rpi_rtc_set_charge_voltage
> >
> > V2 -> V3:
> > - Move platform check to firmware and abort before registering
> > a platform device if on another platform
> > - Add a dependency on the Raspberry Pi firmware to Kconfig
> > - Check return value of devm_device_init_wakeup
> > - Fix property name
> >
> > V1 -> V2:
> > Instead of the original driver, which was directly bound to the device tree.
> > This driver is bound to the Raspberry Pi firmware device by creating
> > a child device in the firmware driver probe function.
> > The child device is then bound to this driver,
> > which uses the firmware mailbox to access the RTC.
> >
> > A couple of minor changes have been made to the driver since it was originally written, including:
> > - Checking if the model is a Raspberry Pi 5, as the RTC is only present on that model.
> > - Using the new devm_rpi_firmware_get() and devm_init_wakeup() helper to get the firmware device and avoid leaking memory.
> > - Using millivolts instead of microvolts for the trickle charge voltage, to match the RTC standard.
> > - Instead of setting the trickle charge voltage to 0 to disable trickle charging, the property is now optional. If the property is not present, trickle charging is disabled, per the RTC standard.
> > - Renaming the driver dt match compatible to "raspberrypi,firmware-rtc" to match the other firmware bindings.
> > - Renaming the driver name to "raspberrypi-rtc" to match the other firmware drivers.
> >
> > drivers/firmware/raspberrypi.c | 24 ++
> > drivers/rtc/Kconfig | 12 +
> > drivers/rtc/Makefile | 1 +
> > drivers/rtc/rtc-raspberrypi.c | 276 +++++++++++++++++++++
> > include/soc/bcm2835/raspberrypi-firmware.h | 2 +
> > 5 files changed, 315 insertions(+)
> > create mode 100644 drivers/rtc/rtc-raspberrypi.c
> >
> > diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> > index 0aa322e9a2e7..f8c83c25eccc 100644
> > --- a/drivers/firmware/raspberrypi.c
> > +++ b/drivers/firmware/raspberrypi.c
> > @@ -24,6 +24,7 @@
> >
> > static struct platform_device *rpi_hwmon;
> > static struct platform_device *rpi_clk;
> > +static struct platform_device *rpi_rtc;
> >
> > struct rpi_firmware {
> > struct mbox_client cl;
> > @@ -231,6 +232,26 @@ static void rpi_register_clk_driver(struct device *dev)
> > -1, NULL, 0);
> > }
> >
> > +static void rpi_register_rtc_driver(struct device *dev)
> > +{
> > + struct device_node *firmware;
> > +
> > + // Check if our model of Raspberry Pi board is from the 5th gen
> > + // as the RTC is only present on that model.
> > + if (!of_machine_is_compatible("brcm,bcm2712"))
> > + return;
> > +
> > + firmware = of_get_compatible_child(dev->of_node,
> > + "raspberrypi,firmware-rtc");
> > + if (firmware) {
> > + of_node_put(firmware);
> > + return;
> > + }
> > +
> > + rpi_rtc = platform_device_register_data(dev, "raspberrypi-rtc",
> > + -1, NULL, 0);
> > +}
> > +
> > unsigned int rpi_firmware_clk_get_max_rate(struct rpi_firmware *fw, unsigned int id)
> > {
> > struct rpi_firmware_clk_rate_request msg =
> > @@ -305,6 +326,7 @@ static int rpi_firmware_probe(struct platform_device *pdev)
> > rpi_firmware_print_firmware_revision(fw);
> > rpi_register_hwmon_driver(dev, fw);
> > rpi_register_clk_driver(dev);
> > + rpi_register_rtc_driver(dev);
> >
> > return 0;
> > }
> > @@ -327,6 +349,8 @@ static void rpi_firmware_remove(struct platform_device *pdev)
> > rpi_hwmon = NULL;
> > platform_device_unregister(rpi_clk);
> > rpi_clk = NULL;
> > + platform_device_unregister(rpi_rtc);
> > + rpi_rtc = NULL;
> >
> > rpi_firmware_put(fw);
> > }
> > diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> > index 05b9233b9418..6dae4c069be2 100644
> > --- a/drivers/rtc/Kconfig
> > +++ b/drivers/rtc/Kconfig
> > @@ -1999,6 +1999,18 @@ config RTC_DRV_R7301
> > This driver can also be built as a module. If so, the module
> > will be called rtc-r7301.
> >
> > +config RTC_DRV_RPI
> > + tristate "Raspberry Pi RTC"
> > + depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
> > + depends on ARCH_BRCMSTB || COMPILE_TEST
> > + default ARCH_BRCMSTB
> > + help
> > + If you say yes here you get support for the RTC found on
> > + Raspberry Pi devices.
> > +
> > + This driver can also be built as a module. If so, the module
> > + will be called rtc-raspberrypi.
> Sorry for my misleading wording. I meant in this case 1 tab and align
> the rest with spaces just like the other.
> ...
> > diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
> > index 975bef529854..e13994d8281c 100644
> > --- a/include/soc/bcm2835/raspberrypi-firmware.h
> > +++ b/include/soc/bcm2835/raspberrypi-firmware.h
> > @@ -75,6 +75,8 @@ enum rpi_firmware_property_tag {
> > RPI_FIRMWARE_GET_THROTTLED = 0x00030046,
> > RPI_FIRMWARE_GET_CLOCK_MEASURED = 0x00030047,
> > RPI_FIRMWARE_NOTIFY_REBOOT = 0x00030048,
> > + RPI_FIRMWARE_GET_RTC_REG = 0x00030087,
> > + RPI_FIRMWARE_SET_RTC_REG = 0x00038087,
> Please try to keep the value order. I know it's already messed up,
> Gregor Herburger send a patch which already address the existing order
> ("firmware: raspberrypi: reorder rpi_firmware_property_tag enum").
>
> Best regards
> > RPI_FIRMWARE_SET_CLOCK_STATE = 0x00038001,
> > RPI_FIRMWARE_SET_CLOCK_RATE = 0x00038002,
> > RPI_FIRMWARE_SET_VOLTAGE = 0x00038003,
>
More information about the linux-arm-kernel
mailing list