Re: [PATCH v4 1/2] dmaengine: tegra210-adma: Fix build error due to 64-by-32 division

Jon Hunter
2025-02-05T11:28:00Z

On 05/02/2025 03:31, 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 div_u64() for the adma address space
>
> Fixes: 68811c928f88 ("dmaengine: tegra210-adma: Support channel page")
> Cc: stable@vger.kernel.org
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202412250204.GCQhdKe3-lkp@intel.com/
> Signed-off-by: Mohan Kumar D <mkumard@nvidia.com>
> ---
> drivers/dma/tegra210-adma.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
> index 6896da8ac7ef..a0bd4822ed80 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;
> + u64 page_no, page_offset;
> + int ret, i;
>
> cdata = of_device_get_match_data(&pdev->dev);
> if (!cdata) {
> @@ -914,10 +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(res_page->start <= res_base->start))
> return -EINVAL;
> - tdma->ch_page_no = page_no - 1;
> +
> + page_offset = res_page->start - res_base->start;
> + page_no = div_u64(page_offset, cdata->ch_base_offset);
> +
> + if (WARN_ON(page_no == 0))
> + return -EINVAL;

Sorry to be pedantic but should this now be ...

if (WARN_ON((page_no == 0) || (page_no > UINT_MAX)))

Jon

> +
> + tdma->ch_page_no = lower_32_bits(page_no) - 1;
> tdma->base_addr = devm_ioremap_resource(&pdev->dev, res_base);
> if (IS_ERR(tdma->base_addr))
> return PTR_ERR(tdma->base_addr);

--
nvpublic