linux-kernel - Re: [PATCH v3 3/6] drm/dp: Add macro to check max

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Message-ID: <CAE-0n52o0FtVhd_TPEf_NhpXwLErcYm9NX+dqW8RnwrYGrM6-Q@mail.gmail.com>
Date:   Wed, 27 Oct 2021 23:31:27 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     robdclark@...il.com, seanpaul@...omium.org,
        kalyan_t@...eaurora.org, abhinavk@...eaurora.org,
        dianders@...omium.org, khsieh@...eaurora.org,
        mkrishn@...eaurora.org, sbillaka@...eaurora.org
Subject: Re: [PATCH v3 3/6] drm/dp: Add macro to check max_downspread capability

Quoting Sankeerth Billakanti (2021-10-27 18:54:45)
> Add a macro to check for the max_downspread capability in
> drm_dp_helper.
>
> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
> ---

Looks OK to me. One question below

Reviewed-by: Stephen Boyd <swboyd@...omium.org>

>  include/drm/drm_dp_helper.h | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index afdf7f4..b39e7a0 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1784,6 +1784,12 @@ drm_dp_tps3_supported(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
>  }
>
>  static inline bool
> +drm_dp_max_downspread(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
> +{
> +       return dpcd[DP_MAX_DOWNSPREAD] & DP_MAX_DOWNSPREAD_0_5;

Does it need a dpcd[DP_DPCD_REV] >= 0x11 check? Reading the spec I think
the answer may be that we check for 1.1 and always return 1 if so just
to make sure devices don't break the spec and put a 0 here when they're
rev is >= v1.1?

> +}
> +
> +static inline bool
>  drm_dp_tps4_supported(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
>  {
>         return dpcd[DP_DPCD_REV] >= 0x14 &&