linux-kernel - Re: [PATCH v5 11/36] drm/bridge: analogix_dp: Wait for HPD signal before configuring link

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Date:   Wed, 14 Mar 2018 11:39:27 +0530
From:   Archit Taneja <architt@...eaurora.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        inki.dae@...sung.com, thierry.reding@...il.com, hjc@...k-chips.com,
        seanpaul@...omium.org, airlied@...ux.ie, tfiga@...omium.org,
        heiko@...ech.de
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        a.hajda@...sung.com, Laurent.pinchart@...asonboard.com,
        ykk@...k-chips.com, kernel@...labora.com, m.szyprowski@...sung.com,
        linux-samsung-soc@...r.kernel.org, jy0922.shim@...sung.com,
        rydberg@...math.org, krzk@...nel.org,
        linux-rockchip@...ts.infradead.org, kgene@...nel.org,
        linux-input@...r.kernel.org, orjan.eide@....com,
        wxt@...k-chips.com, jeffy.chen@...k-chips.com,
        Stéphane Marchesin <marcheu@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, mark.yao@...k-chips.com,
        wzz@...k-chips.com, hl@...k-chips.com, jingoohan1@...il.com,
        sw0312.kim@...sung.com, dianders@...omium.org,
        kyungmin.park@...sung.com, kuankuan.y@...il.com, hshi@...omium.org
Subject: Re: [PATCH v5 11/36] drm/bridge: analogix_dp: Wait for HPD signal
 before configuring link



On Saturday 10 March 2018 03:53 AM, Enric Balletbo i Serra wrote:
> From: zain wang <wzz@...k-chips.com>
> 
> According to DP spec v1.3 chap 3.5.1.2 Link Training, Link Policy Maker
> must first detect that the HPD signal is asserted high by the Downstream
> Device before establishing a link with it.

Reviewed-by: Archit Taneja <architt@...eaurora.org>

Thanks,
Archit

> 
> Cc: Stéphane Marchesin <marcheu@...omium.org>
> Signed-off-by: zain wang <wzz@...k-chips.com>
> Signed-off-by: Sean Paul <seanpaul@...omium.org>
> Signed-off-by: Thierry Escande <thierry.escande@...labora.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
> 
>   drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index c81733b8185e..92fb9a072cb6 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -1169,6 +1169,17 @@ static int analogix_dp_set_bridge(struct analogix_dp_device *dp)
>   	if (ret)
>   		goto out_dp_init;
>   
> +	/*
> +	 * According to DP spec v1.3 chap 3.5.1.2 Link Training,
> +	 * We should first make sure the HPD signal is asserted high by device
> +	 * when we want to establish a link with it.
> +	 */
> +	ret = analogix_dp_detect_hpd(dp);
> +	if (ret) {
> +		DRM_ERROR("failed to get hpd single ret = %d\n", ret);
> +		goto out_dp_init;
> +	}
> +
>   	ret = analogix_dp_commit(dp);
>   	if (ret)
>   		goto out_dp_init;
>