From 0ab46a83fa124a71e95728dd31cf0feab4da7c12 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ren=C3=AA=20de=20Souza=20Pinto?= Date: Tue, 4 Aug 2026 12:39:57 +0200 Subject: [PATCH] watchdog: wdat_wdt: map registers that fall inside ACPI NVS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some firmwares describe WDAT registers inside memory ranges marked as ACPI NVS in the E820 map, failing with -EBUSY during probe, leaving the hardware watchdog unserviced and triggering periodic system resets. This issue was observed on a OnLogic Karbon 524 device (when watchdog is enabled in BIOS): wdat_wdt wdat_wdt: error -EBUSY: can't request region for resource [mem 0x63df7a98] wdat_wdt wdat_wdt: probe with driver wdat_wdt failed with error -16 Check whether the region falls inside ACPI NVS before requesting it and, if so, map it without reservation. Signed-off-by: Renê de Souza Pinto Link: https://lore.kernel.org/r/20260804103958.3684195-1-rene@renesp.com.br Signed-off-by: Guenter Roeck --- drivers/watchdog/wdat_wdt.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/drivers/watchdog/wdat_wdt.c b/drivers/watchdog/wdat_wdt.c index dd3c2d69c9df..55ea16e73652 100644 --- a/drivers/watchdog/wdat_wdt.c +++ b/drivers/watchdog/wdat_wdt.c @@ -7,7 +7,9 @@ */ #include +#include #include +#include #include #include #include @@ -309,6 +311,29 @@ static struct watchdog_ops wdat_wdt_ops = { .set_timeout = wdat_wdt_set_timeout, }; +static void __iomem *wdat_wdt_map_mem(struct device *dev, struct resource *res) +{ + resource_size_t size = resource_size(res); + void *addr; + + /* Map memory region without reserving it if it falls inside ACPI NVS */ + if (region_intersects(res->start, size, IORESOURCE_MEM, + IORES_DESC_ACPI_NV_STORAGE) == REGION_INTERSECTS) { + dev_warn(dev, "%pR is inside ACPI NVS, mapping without reservation\n", + res); + + addr = devm_memremap(dev, res->start, size, MEMREMAP_WB); + if (IS_ERR(addr)) { + dev_err(dev, "failed to map resource %pR\n", res); + return IOMEM_ERR_PTR(PTR_ERR(addr)); + } + + return (void __iomem __force *)addr; + } + + return devm_ioremap_resource(dev, res); +} + static int wdat_wdt_probe(struct platform_device *pdev) { struct device *dev = &pdev->dev; @@ -362,7 +387,7 @@ static int wdat_wdt_probe(struct platform_device *pdev) res = &pdev->resource[i]; if (resource_type(res) == IORESOURCE_MEM) { - reg = devm_ioremap_resource(dev, res); + reg = wdat_wdt_map_mem(dev, res); if (IS_ERR(reg)) { ret = PTR_ERR(reg); goto out_put_table;