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

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Message-ID: <Z6ncuLHotCAw61b5@vaman>
Date: Mon, 10 Feb 2025 16:32:16 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Mohan Kumar D <mkumard@...dia.com>
Cc: thierry.reding@...il.com, jonathanh@...dia.com,
	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 v4 1/2] dmaengine: tegra210-adma: Fix build error due to
 64-by-32 division

Hi Mohan,

On 05-02-25, 09:01, 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.

Patch should describe the change! Please revise subject to describe that
and not fix build error... This can come in changelog and below para is
apt

> 
>    "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@...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 | 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;
> +
> +			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);
> -- 
> 2.25.1

-- 
~Vinod