linux-kernel - Re: [PATCH] media: hantro: Auto generate the AXI ID to avoid conflicts

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Date:   Thu, 25 Feb 2021 21:07:05 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        fbuergisser@...gle.com, Doug Anderson <dianders@...gle.com>,
        Collabora Kernel ML <kernel@...labora.com>,
        acourbot@...gle.com, tfiga@...gle.com,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        devel@...verdev.osuosl.org,
        linux-media <linux-media@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] media: hantro: Auto generate the AXI ID to avoid conflicts

Hi Enric,

Thanks a lot for the patch.

On Thu, 25 Feb 2021 at 09:08, Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> The AXI ID is an AXI bus configuration for improve bus performance. If
> read and write operations use different ID the operations can be
> paralleled, whereas when they have the same ID the operations will be
> serialized. Right now, the write ID is fixed to 0 but we can set it to
> 0xff to get auto generated ID to avoid possible conflicts.
>
> This change has no functional changes, but seems reasonable to let the
> hardware to autogenerate the ID instead of hardcoding in software.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
>
>  drivers/staging/media/hantro/hantro_g1_h264_dec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/staging/media/hantro/hantro_g1_h264_dec.c b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> index 845bef73d218..090088cd98ea 100644
> --- a/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> +++ b/drivers/staging/media/hantro/hantro_g1_h264_dec.c
> @@ -30,7 +30,7 @@ static void set_params(struct hantro_ctx *ctx)
>         u32 reg;
>
>         /* Decoder control register 0. */
> -       reg = G1_REG_DEC_CTRL0_DEC_AXI_WR_ID(0x0);
> +       reg = G1_REG_DEC_CTRL0_DEC_AXI_WR_ID(0xff);

Can we define a macro to avoid this magic number,
and add some comments explaining what's 0xff for?

Given this is AXI configuration, I'd expect it's CODEC-agnostic.
Maybe we could move CODEC-agnostic path to avoid duplicating the code?

Does this change apply to the rkvdec driver?

Thanks,
Ezequiel