linux-kernel - [PATCH v1 1/1] rtc: zynqmp: ensure correct RTC calibration

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250804154750.28249-2-l.rubusch@gmail.com>
Date: Mon,  4 Aug 2025 15:47:50 +0000
From: Lothar Rubusch <l.rubusch@...il.com>
To: alexandre.belloni@...tlin.com,
	michal.simek@....com,
	srinivas.neeli@...inx.com
Cc: linux-rtc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	l.rubusch@...il.com,
	Ivan Vera <ivan.vera@...lustra.com>
Subject: [PATCH v1 1/1] rtc: zynqmp: ensure correct RTC calibration

From: Ivan Vera <ivan.vera@...lustra.com>

In the event of an uninitialized calibration register, ensure the register
is reset and properly programmed during the probe sequence.

At present, only the calibration register is evaluated. If it holds invalid
values after a power cycle, there's no longer a way to reset it, for
instance, via a devicetree entry to 0x7FFF. This issue is documented here:
https://adaptivesupport.amd.com/s/article/000036886?language=en_US 

The fix prioritizes an optional calibration value provided via the
devicetree over the value in the register.

Fixes: 07dcc6f9c76275d6679f28a69e042a2f9dc8f128 ("rtc: zynqmp: Add calibration set and get support")
Signed-off-by: Ivan Vera <ivan.vera@...lustra.com>
Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
---
 drivers/rtc/rtc-zynqmp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index f39102b66eac..0c063c3fae52 100644
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c
@@ -331,9 +331,9 @@ static int xlnx_rtc_probe(struct platform_device *pdev)
 		if (ret)
 			xrtcdev->freq = RTC_CALIB_DEF;
 	}
-	ret = readl(xrtcdev->reg_base + RTC_CALIB_RD);
-	if (!ret)
-		writel(xrtcdev->freq, (xrtcdev->reg_base + RTC_CALIB_WR));
+
+	/* Enable unconditional re-calibration to RTC_CALIB_DEF or DTB entry. */
+	writel(xrtcdev->freq, xrtcdev->reg_base + RTC_CALIB_WR);
 
 	xlnx_init_rtc(xrtcdev);
 
-- 
2.39.5