Re: [PATCH v3 1/2] dmaengine: tegra210-adma: Fix build error due to 64-by-32 division

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On 16/01/2025 16:20, Mohan Kumar D wrote:
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")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202412250204.GCQhdKe3-lkp@xxxxxxxxx/
Signed-off-by: Mohan Kumar D <mkumard@xxxxxxxxxx>
---
  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))


Reviewed-by: Jon Hunter <jonathanh@xxxxxxxxxx>

Thanks!
Jon

--
nvpublic





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