linux-kernel - Re: [PATCH v3 6/6] mmc: tmio: refactor CLK

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Date:   Thu, 30 Aug 2018 14:30:29 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 6/6] mmc: tmio: refactor CLK_CTL bit calculation

On 23 August 2018 at 06:44, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>   for (clk = 0x80000080; new_clock >= (clock << 1); clk >>= 1)
>           clock <<= 1;
>
> ... is too tricky, hence I replaced with
>
>   roundup_pow_of_two(divisor) >> 2
>
> '(clk >> 22) & 0x1' is the bit test for the 1/1 divisor, but
> it is not clear.  'divisor <= 1' is easier to understand.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>

Applied for next, thanks!

Kind regards
Uffe

> ---
>
> Changes in v3: None
> Changes in v2: None
>
>  drivers/mmc/host/tmio_mmc.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/host/tmio_mmc.c b/drivers/mmc/host/tmio_mmc.c
> index b031a77..e04c322 100644
> --- a/drivers/mmc/host/tmio_mmc.c
> +++ b/drivers/mmc/host/tmio_mmc.c
> @@ -48,19 +48,27 @@ static void tmio_mmc_clk_stop(struct tmio_mmc_host *host)
>  static void tmio_mmc_set_clock(struct tmio_mmc_host *host,
>                                unsigned int new_clock)
>  {
> -       u32 clk = 0, clock;
> +       unsigned int clock, divisor;
> +       u32 clk = 0;
> +       int clk_sel;
>
>         if (new_clock == 0) {
>                 tmio_mmc_clk_stop(host);
>                 return;
>         }
>
> -       clock = host->mmc->f_min;
> +       divisor = host->pdata->hclk / new_clock;
>
> -       for (clk = 0x80000080; new_clock >= (clock << 1); clk >>= 1)
> -               clock <<= 1;
> +       if (divisor <= 1) {
> +               clk_sel = 1;
> +               clk = 0;
> +       } else {
> +               clk_sel = 0;
> +               /* bit7 set: 1/512, ... bit0 set:1/4, all bits clear: 1/2 */
> +               clk = roundup_pow_of_two(divisor) >> 2;
> +       }
>
> -       host->pdata->set_clk_div(host->pdev, (clk >> 22) & 1);
> +       host->pdata->set_clk_div(host->pdev, clk_sel);
>
>         sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, ~CLK_CTL_SCLKEN &
>                         sd_ctrl_read16(host, CTL_SD_CARD_CLK_CTL));
> --
> 2.7.4
>