Re: [PATCH 5/5] lib: math64: sync <linux/math64.h> with Linux v7.1

On 2026-07-30T18:40:37, Alexey Charkov <[email protected]> wrote:
> lib: math64: sync <linux/math64.h> with Linux v7.1
>
> U-Boot's copy was last synced with Linux in 2017 by commit 0342e335ba88
> ("lib: div64: sync with Linux"). Since then it has only been touched
> twice locally, and both times in ways that increased the divergence
> rather than tracking upstream. Take the file from the v7.1 tag.
>
> The immediate motivation is DIV64_U64_ROUND_UP(). Commit 3adc17f60bf8
> ("lib: div64: Add support for round up of div64_u64") added it inside
> the #if BITS_PER_LONG == 64 branch, whereas Linux defines it
> unconditionally after that block. Any 32-bit user therefore fails to
> compile:
>
>   error: implicit declaration of function 'DIV64_U64_ROUND_UP';
>   did you mean 'DIV_ROUND_UP'?
>
> This has been surfaced while reworking fractional PLL logic for Rockchip
> RK3588/RK3576, which unexpectedly failed to compile on 32-bit variants [1].
>
> Newly available as a result: DIV64_U64_ROUND_UP() on 32-bit,
> DIV_U64_ROUND_UP(), DIV64_U64_ROUND_CLOSEST(), DIV_U64_ROUND_CLOSEST(),
> DIV_S64_ROUND_CLOSEST(), roundup_u64(), add_u64_u32() and
> mul_s64_u64_shr(), plus upstream's kernel-doc for everything that was
> already here and __always_inline on mul_u64_u32_shr()/mul_u64_u64_shr().
>
> The file is otherwise a verbatim copy of v7.1. Four deviations:
>
>  - The includes. U-Boot has no <linux/math.h>, no <asm/div64.h> and no
>    <vdso/math64.h>. do_div() comes from U-Boot's <div64.h>,
>    BITS_PER_LONG from <linux/bitops.h>, and abs64() from
>    <linux/kernel.h>, which is where U-Boot keeps the rest of what
>    upstream puts in <linux/math.h>.
>
>  - mul_s64_u64_shr() uses abs64() rather than abs(), because U-Boot's
>    abs() evaluates its argument as int for anything that is not a long.
>
>  - mul_u64_add_u64_div_u64() and the mul_u64_u64_div_u64() and
>    mul_u64_u64_div_u64_roundup() macros built on it are not ported.
>    They would need ~110 lines of lib/math/div64.c brought along, plus a
>    u128 type and OPTIMIZER_HIDE_VAR(), and U-Boot has no users for them
>    yet.
>
>  - abs_diff(), added locally by commit f1f4a1d1d835 ("compat: math64:
>    add abs_diff()"), is kept. Upstream has it in <linux/math.h>.
>
> Build tested for evb-rk3288-rk808 (32-bit LE), generic-rk3576 (64-bit
> LE), malta (32-bit BE, which is what compiles the __BIG_ENDIAN union
> paths in mul_u64_u64_shr() and mul_u64_u32_div()), sandbox and
> tools-only, with both gcc and clang. All six DIV*_ROUND_* macros plus
> roundup_u64(), mul_s64_u64_shr(), add_u64_u32() and abs_diff() were
> additionally instantiated on 32-bit ARM to confirm they now resolve.
>
> Closes: https://patchwork.ozlabs.org/project/uboot/patch/[email protected]/#3731361 [1]
> Signed-off-by: Alexey Charkov <[email protected]>
>
> include/linux/math64.h | 182 ++++++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 171 insertions(+), 11 deletions(-)

Reviewed-by: Simon Glass <[email protected]>