linux-kernel - RE: [PATCH 1/4] rtc: zynqmp: correct frequency value

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Message-ID:
 <LV5PR12MB980479009955E816E72E6EA892A3A@LV5PR12MB9804.namprd12.prod.outlook.com>
Date: Tue, 9 Dec 2025 16:51:09 +0000
From: "T, Harini" <Harini.T@....com>
To: Tomas Melin <tomas.melin@...sala.com>, Alexandre Belloni
	<alexandre.belloni@...tlin.com>, "Simek, Michal" <michal.simek@....com>
CC: "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/4] rtc: zynqmp: correct frequency value

[Public]

Hi,

> -----Original Message-----
> From: Tomas Melin <tomas.melin@...sala.com>
> Sent: Monday, December 1, 2025 6:20 PM
> To: Alexandre Belloni <alexandre.belloni@...tlin.com>; Simek, Michal
> <michal.simek@....com>
> Cc: linux-rtc@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org; Tomas Melin <tomas.melin@...sala.com>
> Subject: [PATCH 1/4] rtc: zynqmp: correct frequency value
>
> Caution: This message originated from an External Source. Use proper
> caution when opening attachments, clicking links, or responding.
>
>
> Fix calibration value in case a clock reference is provided.
> The actual calibration value written into register is
> frequency - 1.
>
> Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
> ---
>  drivers/rtc/rtc-zynqmp.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
> index
> 3baa2b481d9f2008750046005283b98a0d546c5c..856bc1678e7d31144f320ae
> 9f75fc58c742a2a64 100644
> --- a/drivers/rtc/rtc-zynqmp.c
> +++ b/drivers/rtc/rtc-zynqmp.c
> @@ -345,7 +345,10 @@ static int xlnx_rtc_probe(struct platform_device
> *pdev)
>                                            &xrtcdev->freq);
>                 if (ret)
>                         xrtcdev->freq = RTC_CALIB_DEF;
> +       } else {
> +               xrtcdev->freq--;
If freq > 65536, the 16-bit register silently truncates.
Please add some checks for above mentioned scenario.
>         }
> +
>         ret = readl(xrtcdev->reg_base + RTC_CALIB_RD);
>         if (!ret)
>                 writel(xrtcdev->freq, (xrtcdev->reg_base + RTC_CALIB_WR));
>
> --
> 2.47.3
>
Thanks,
Harini T