[PATCH v4 0/5] rtc: zynqmp: fixes for read and set offset

[T, Harini]

[Public]

The patch series looks fine to me.

Thanks,
Harini T

> -----Original Message-----
> From: Tomas Melin <tomas.melin at vaisala.com>
> Sent: Thursday, January 22, 2026 7:24 PM
> To: Alexandre Belloni <alexandre.belloni at bootlin.com>; Simek, Michal
> <michal.simek at amd.com>
> Cc: linux-rtc at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org; Tomas Melin <tomas.melin at vaisala.com>; T, Harini
> <Harini.T at amd.com>
> Subject: [PATCH v4 0/5] rtc: zynqmp: fixes for read and set offset
>
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
>
>
> Add improvements for read and set offset functions.
> The basic functionality is still the same, but offset correction values are now
> updated to match with expected.
>
> The RTC calibration value operates with full ticks, and fractional ticks which
> are a 1/16 of a full tick.
> The 16 lowest bits in the calibration registers are for the full ticks and value
> matches the external oscillator in Hz. Through that, the maximum and
> minimum offset values can be calculated dynamically, as they depend on the
> input frequency used.
>
> For docs on the calibration register, see https://docs.amd.com/r/en-
> US/ug1087-zynq-ultrascale-registers/CALIB_READ-RTC-Register
>
> Due to rounding errors (different number of fract ticks), offset readback will
> differ slightly depending on if the offset is negative or positive. This is
> however well below the granularity provided by the hardware.
>
> For example
> $ echo 34335 > offset
> $ cat offset
> 34335
> $ echo -34335 > offset
> $ cat offset
> -34326
>
> Signed-off-by: Tomas Melin <tomas.melin at vaisala.com>
> ---
> Changes in v4:
> - Do not limit building to zynqmp arch as building on other platforms
>   might be needed. Implies dropping commit.
> - No need for RTC_PPB to be 64 bit value, use 32 bit instead
> - Link to v3: https://lore.kernel.org/r/20260119-zynqmp-rtc-updates-v3-0-
> acd902fdeab1 at vaisala.com
>
> Changes in v3:
> - Add commit for limiting building of driver to zynqmp arch.
> - Reorder variable declarations in set_offset
> - Link to v2: https://lore.kernel.org/r/20260108-zynqmp-rtc-updates-v2-0-
> 864c161fa83d at vaisala.com
>
> Changes in v2:
> - Add commit introducing check for calibration value overflow
> - Update comments
> - Align data types across set and read
> - Rename fract_tick as fract_data conforming to data sheet
> - Further improve on set offset calculation logic
> - Link to v1: https://lore.kernel.org/r/20251201-zynqmp-rtc-updates-v1-0-
> 33875c1e385b at vaisala.com
>
> ---
> Tomas Melin (5):
>       rtc: zynqmp: correct frequency value
>       rtc: zynqmp: check calibration max value
>       rtc: zynqmp: rework read_offset
>       rtc: zynqmp: rework set_offset
>       rtc: zynqmp: use dynamic max and min offset ranges
>
>  drivers/rtc/rtc-zynqmp.c | 75 ++++++++++++++++++++++++++---------------------
> -
>  1 file changed, 41 insertions(+), 34 deletions(-)
> ---
> base-commit: cd635e33b0113287c94021be53d2a7c61a1614e9
> change-id: 20251201-zynqmp-rtc-updates-d260364cc01b
>
> Best regards,
> --
> Tomas Melin <tomas.melin at vaisala.com>