linux-kernel - [PATCH 1/2] dmaengine: tegra210-adma: Fix build error due to 64-by-32 division

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Message-ID: <20250116154439.3889536-2-mkumard@nvidia.com>
Date: Thu, 16 Jan 2025 21:14:38 +0530
From: Mohan Kumar D <mkumard@...dia.com>
To: <vkoul@...nel.org>, <thierry.reding@...il.com>, <jonathanh@...dia.com>
CC: <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>, Mohan Kumar D
	<mkumard@...dia.com>, kernel test robot <lkp@...el.com>
Subject: [PATCH 1/2] dmaengine: tegra210-adma: Fix build error due to 64-by-32 division

Kernel test robot reported the build errors on 32-bit platforms due to
plain 64-by-32 division. Following build erros were reported.

   "ERROR: modpost: "__udivdi3" [drivers/dma/tegra210-adma.ko] undefined!
    ld: drivers/dma/tegra210-adma.o: in function `tegra_adma_probe':
    tegra210-adma.c:(.text+0x12cf): undefined reference to `__udivdi3'"

This can be fixed by using lower_32_bits() for the adma address space as
the offset is constrained to the lower 32 bits

Fixes: 68811c928f88 ("dmaengine: tegra210-adma: Support channel page")
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412250204.GCQhdKe3-lkp@intel.com/
Signed-off-by: Mohan Kumar D <mkumard@...dia.com>
---
 drivers/dma/tegra210-adma.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
index 6896da8ac7ef..258220c9cb50 100644
--- a/drivers/dma/tegra210-adma.c
+++ b/drivers/dma/tegra210-adma.c
@@ -887,7 +887,8 @@ static int tegra_adma_probe(struct platform_device *pdev)
 	const struct tegra_adma_chip_data *cdata;
 	struct tegra_adma *tdma;
 	struct resource *res_page, *res_base;
-	int ret, i, page_no;
+	unsigned int page_no, page_offset;
+	int ret, i;
 
 	cdata = of_device_get_match_data(&pdev->dev);
 	if (!cdata) {
@@ -914,9 +915,16 @@ static int tegra_adma_probe(struct platform_device *pdev)
 
 		res_base = platform_get_resource_byname(pdev, IORESOURCE_MEM, "global");
 		if (res_base) {
-			page_no = (res_page->start - res_base->start) / cdata->ch_base_offset;
-			if (page_no <= 0)
+			if (WARN_ON(lower_32_bits(res_page->start) <=
+						lower_32_bits(res_base->start)))
+				return -EINVAL;
+
+			page_offset = lower_32_bits(res_page->start) -
+						lower_32_bits(res_base->start);
+			page_no = page_offset / cdata->ch_base_offset;
+			if (page_no == 0)
 				return -EINVAL;
+
 			tdma->ch_page_no = page_no - 1;
 			tdma->base_addr = devm_ioremap_resource(&pdev->dev, res_base);
 			if (IS_ERR(tdma->base_addr))
-- 
2.25.1