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

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Message-ID: <ea04c16a-67c9-4ec6-8dd0-54c18bac87d9@nvidia.com>
Date: Fri, 17 Jan 2025 14:52:16 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Mohan Kumar D <mkumard@...dia.com>, vkoul@...nel.org,
 thierry.reding@...il.com
Cc: dmaengine@...r.kernel.org, linux-tegra@...r.kernel.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org,
 kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v3 1/2] dmaengine: tegra210-adma: Fix build error due to
 64-by-32 division


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@...r.kernel.org
> 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))


Reviewed-by: Jon Hunter <jonathanh@...dia.com>

Thanks!
Jon

-- 
nvpublic