Re: [PATCH v3] hw/net: cadence_gem: feat: add logic for the DISABLE_MASK bit in type2_compare_x_word_1

[Peter Maydell]

Edgar or Alistair -- could one of you review this
cadence GEM patch, please?

On Thu, 19 Dec 2024 at 06:17, Andrew.Yuan <andrew.yuan@jaguarmicro.com> wrote:
>
> From: Andrew Yuan <andrew.yuan@jaguarmicro.com>
>
> As in the Cadence IP for Gigabit Ethernet MAC Part Number: IP7014 IP Rev: 
> R1p12 - Doc Rev: 1.3 User Guide,
> if the DISABLE_MASK bit in type2_compare_x_word_1 is set,
> mask_value in type2_compare_x_word_0 is used as an additional 2 byte Compare 
> Value
>
> Signed-off-by: Andrew Yuan <andrew.yuan@jaguarmicro.com>
> Suggested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  hw/net/cadence_gem.c | 24 +++++++++++++++++++-----
>  1 file changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
> index 3fce01315f..7bd176951e 100644
> --- a/hw/net/cadence_gem.c
> +++ b/hw/net/cadence_gem.c
> @@ -909,8 +909,8 @@ static int get_queue_from_screen(CadenceGEMState *s, 
> uint8_t *rxbuf_ptr,
>
>          /* Compare A, B, C */
>          for (j = 0; j < 3; j++) {
> -            uint32_t cr0, cr1, mask, compare;
> -            uint16_t rx_cmp;
> +            uint32_t cr0, cr1, mask, compare, disable_mask;
> +            uint32_t rx_cmp;
>              int offset;
>              int cr_idx = extract32(reg, 
> R_SCREENING_TYPE2_REG0_COMPARE_A_SHIFT + j * 6,
>                                     R_SCREENING_TYPE2_REG0_COMPARE_A_LENGTH);
> @@ -946,9 +946,23 @@ static int get_queue_from_screen(CadenceGEMState *s, 
> uint8_t *rxbuf_ptr,
>                  break;
>              }
>
> -            rx_cmp = rxbuf_ptr[offset] << 8 | rxbuf_ptr[offset];
> -            mask = FIELD_EX32(cr0, TYPE2_COMPARE_0_WORD_0, MASK_VALUE);
> -            compare = FIELD_EX32(cr0, TYPE2_COMPARE_0_WORD_0, COMPARE_VALUE);
> +            disable_mask =
> +                FIELD_EX32(cr1, TYPE2_COMPARE_0_WORD_1, DISABLE_MASK);
> +            if (disable_mask) {
> +                /*
> +                 * If disable_mask is set,
> +                 * mask_value is used as an additional 2 byte Compare Value.
> +                 * To simple, set mask = 0xFFFFFFFF, if disable_mask is set.
> +                 */
> +                rx_cmp = ldl_le_p(rxbuf_ptr + offset);
> +                mask = 0xFFFFFFFF;
> +                compare = cr0;
> +            } else {
> +                rx_cmp = lduw_le_p(rxbuf_ptr + offset);

Is the change in behaviour in the !disable_mask codepath here
intentional? Previously we use one byte from rxbuf_ptr[offset],
duplicated into both halves of rx_cmp; now we will load two
different bytes from rxbuf_ptr[offset] and rxbuf_ptr[offset + 1].

If this is intended, we should say so in the commit message.


> +                mask = FIELD_EX32(cr0, TYPE2_COMPARE_0_WORD_0, MASK_VALUE);
> +                compare =
> +                    FIELD_EX32(cr0, TYPE2_COMPARE_0_WORD_0, COMPARE_VALUE);
> +            }
>
>              if ((rx_cmp & mask) == (compare & mask)) {
>                  matched = true;
> --
> 2.25.1

thanks
-- PMM