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: <2d190825-5284-4ac6-9735-051849bc9bb6@nvidia.com>
Date: Mon, 10 Feb 2025 16:45:53 +0530
From: Mohan Kumar D <mkumard@...dia.com>
To: Vinod Koul <vkoul@...nel.org>
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


On 10-02-2025 16:32, Vinod Koul wrote:
> External email: Use caution opening links or attachments
>
>
> 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
Sure, Will update the subject and resend the updated patch
>>     "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