linux-kernel - Re: [net-next PATCH 1/2] mlxsw: spectrum_kvdl: use div

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Date:   Sun, 25 Feb 2018 12:04:10 +0200
From:   Arkadi Sharshevsky <arkadis@...lanox.com>
To:     Arnd Bergmann <arnd@...db.de>, Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Wei Yongjun <weiyongjun1@...wei.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH 1/2] mlxsw: spectrum_kvdl: use div_u64() for
 64-bit division



On 02/23/2018 03:15 PM, Arnd Bergmann wrote:
> Calculating the number of entries now uses 64-bit arithmetic that
> causes a link error on 32-bit architectures:
> 
> drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.o: In function `mlxsw_sp_kvdl_init':
> spectrum_kvdl.c:(.text+0x51c): undefined reference to `__aeabi_uldivmod'
> 
> We could probably use a 32-bit division here as before, but since this is
> not in a performance critical path, div_u64() seems cleaner here.
> 
> Fixes: 887839e6960d ("mlxsw: spectrum_kvdl: Add support for dynamic partition set")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c
> index d27fa57ad3c3..6fd701db90c9 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c
> @@ -278,7 +278,7 @@ static int mlxsw_sp_kvdl_part_init(struct mlxsw_sp *mlxsw_sp,
>  		resource_size = info->end_index - info->start_index + 1;
>  	}
>  
> -	nr_entries = resource_size / info->alloc_size;
> +	nr_entries = div_u64(resource_size, info->alloc_size);
>  	usage_size = BITS_TO_LONGS(nr_entries) * sizeof(unsigned long);
>  	part = kzalloc(sizeof(*part) + usage_size, GFP_KERNEL);
>  	if (!part)
> 

Acked-by: Arkadi Sharshevsky <arkadis@...lanox.com>