linux-kernel - Re: [PATCH v5 2/2] mmc: core: Optimize the mmc erase size alignment

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Date:   Fri, 9 Sep 2016 11:46:21 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Doug Anderson <dianders@...omium.org>,
        Heiko Stübner <heiko@...ech.de>,
        David Jander <david@...tonic.nl>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v5 2/2] mmc: core: Optimize the mmc erase size alignment

On 7 September 2016 at 04:38, Baolin Wang <baolin.wang@...aro.org> wrote:
> In most cases the 'card->erase_size' is power of 2, then the round_up/down()
> function is more efficient than '%' operation when the 'card->erase_size' is
> power of 2.
>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> Tested-by: Shawn Lin <shawn.lin@...k-chips.com>

Thanks, applied for next!

Kind regards
Uffe

> ---
>  drivers/mmc/core/core.c |   34 ++++++++++++++++++++++++++--------
>  1 file changed, 26 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 11b4897..4264ac6 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2209,19 +2209,37 @@ static unsigned int mmc_align_erase_size(struct mmc_card *card,
>  {
>         unsigned int from_new = *from, nr_new = nr, rem;
>
> -       rem = from_new % card->erase_size;
> -       if (rem) {
> -               rem = card->erase_size - rem;
> -               from_new += rem;
> +       /*
> +        * When the 'card->erase_size' is power of 2, we can use round_up/down()
> +        * to align the erase size efficiently.
> +        */
> +       if (is_power_of_2(card->erase_size)) {
> +               unsigned int temp = from_new;
> +
> +               from_new = round_up(temp, card->erase_size);
> +               rem = from_new - temp;
> +
>                 if (nr_new > rem)
>                         nr_new -= rem;
>                 else
>                         return 0;
> -       }
>
> -       rem = nr_new % card->erase_size;
> -       if (rem)
> -               nr_new -= rem;
> +               nr_new = round_down(nr_new, card->erase_size);
> +       } else {
> +               rem = from_new % card->erase_size;
> +               if (rem) {
> +                       rem = card->erase_size - rem;
> +                       from_new += rem;
> +                       if (nr_new > rem)
> +                               nr_new -= rem;
> +                       else
> +                               return 0;
> +               }
> +
> +               rem = nr_new % card->erase_size;
> +               if (rem)
> +                       nr_new -= rem;
> +       }
>
>         if (nr_new == 0)
>                 return 0;
> --
> 1.7.9.5
>