[PATCH 03/20] common/cnxk: adjust shaper rates to lower boundaries

[Jerin Jacob]

On Mon, Feb 7, 2022 at 1:00 PM Nithin Dabilpuram
<ndabilpuram at marvell.com> wrote:
>
> From: Satha Rao <skoteshwar at marvell.com>
>
> New api to get floor values for a requested shaper rate, which can assure

Since it is internal API, no need to mention in the comment log

> packets should never be transmitted at a rate higher than configured.
>
> Keep the old api to get HW suggested values.
> And introduce new parameter to select appropriate api.

api -> API

>
> Signed-off-by: Satha Rao <skoteshwar at marvell.com>
> ---
> +static uint64_t
> +nix_tm_shaper_rate_conv_floor(uint64_t value, uint64_t *exponent_p,
> +                             uint64_t *mantissa_p, uint64_t *div_exp_p)
> +{
> +       uint64_t div_exp, exponent, mantissa;
> +
> +       /* Boundary checks */
> +       if (value < NIX_TM_MIN_SHAPER_RATE || value > NIX_TM_MAX_SHAPER_RATE)
> +               return 0;
> +
> +       if (value <= NIX_TM_SHAPER_RATE(0, 0, 0)) {
> +               /* Calculate rate div_exp and mantissa using
> +                * the following formula:
> +                *
> +                * value = (2E6 * (256 + mantissa)
> +                *              / ((1 << div_exp) * 256))
> +                */
> +               div_exp = 0;
> +               exponent = 0;
> +               mantissa = NIX_TM_MAX_RATE_MANTISSA;
> +
> +               while (value <= (NIX_TM_SHAPER_RATE_CONST / (1 << div_exp)))
> +                       div_exp += 1;
> +
> +               while (value <= ((NIX_TM_SHAPER_RATE_CONST * (256 + mantissa)) /
> +                                ((1 << div_exp) * 256)))
> +                       mantissa -= 1;

Please move this as another static function.


> +       } else {
> +               /* Calculate rate exponent and mantissa using
> +                * the following formula:
> +                *
> +                * value = (2E6 * ((256 + mantissa) << exponent)) / 256
> +                *
> +                */
> +               div_exp = 0;
> +               exponent = NIX_TM_MAX_RATE_EXPONENT;
> +               mantissa = NIX_TM_MAX_RATE_MANTISSA;
> +
> +               while (value <= (NIX_TM_SHAPER_RATE_CONST * (1 << exponent)))
> +                       exponent -= 1;
> +
> +               while (value <= ((NIX_TM_SHAPER_RATE_CONST *
> +                                 ((256 + mantissa) << exponent)) /
> +                                256))
> +                       mantissa -= 1;

Please move this as another static function.

> +       }
> +
> +       if (div_exp > NIX_TM_MAX_RATE_DIV_EXP ||
> +           exponent > NIX_TM_MAX_RATE_EXPONENT ||
> +           mantissa > NIX_TM_MAX_RATE_MANTISSA)
> +               return 0;
> +
> +       if (div_exp_p)
> +               *div_exp_p = div_exp;
> +       if (exponent_p)
> +               *exponent_p = exponent;
> +       if (mantissa_p)
> +               *mantissa_p = mantissa;
> +
> +       /* Calculate real rate value */
> +       return NIX_TM_SHAPER_RATE(exponent, mantissa, div_exp);
> +}
> +
> +static uint64_t
> +nix_tm_shaper_rate_conv_exact(uint64_t value, uint64_t *exponent_p,
> +                             uint64_t *mantissa_p, uint64_t *div_exp_p)
>  {
>         uint64_t div_exp, exponent, mantissa;
>
> @@ -188,6 +251,23 @@ nix_tm_shaper_rate_conv(uint64_t value, uint64_t *exponent_p,
>         return NIX_TM_SHAPER_RATE(exponent, mantissa, div_exp);
>  }
>
> +/* With zero accuracy we will tune parameters as defined by HW,
> + * non zero accuracy will keep the parameters close to lower values
> + * and make sure long term shaper rate will not exceed requested rate.

long-term
requested -> the requested