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

[Jon Hunter]

On 05/02/2025 11:27, Jon Hunter wrote:
> 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@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 | 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)))

Nevermind, patch 2/2 addresses this.

Jon

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