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Date:   Mon, 29 Jan 2018 16:38:24 -0500
From:   Sean Paul <seanpaul@chromium.org>
To:     Thierry Escande <thierry.escande@collabora.com>
Cc:     Archit Taneja <architt@codeaurora.org>,
        Inki Dae <inki.dae@samsung.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Sandy Huang <hjc@rock-chips.com>,
        Sean Paul <seanpaul@chromium.org>,
        David Airlie <airlied@linux.ie>,
        Tomasz Figa <tfiga@chromium.org>,
        Haixia Shi <hshi@chromium.org>,
        =?iso-8859-1?Q?=D8rjan?= Eide <orjan.eide@arm.com>,
        Zain Wang <wzz@rock-chips.com>,
        Yakir Yang <ykk@rock-chips.com>, Lin Huang <hl@rock-chips.com>,
        Douglas Anderson <dianders@chromium.org>,
        Mark Yao <mark.yao@rock-chips.com>,
        linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
        dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 29/43] drm/bridge: analogix_dp: Move fast link
 training detect to set_bridge
Message-ID: <20180129213824.6jzjxz4gfoyytq7w@art_vandelay>
References: <20180126131710.7622-1-thierry.escande@collabora.com>
 <20180126131710.7622-30-thierry.escande@collabora.com>
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On Fri, Jan 26, 2018 at 02:16:56PM +0100, Thierry Escande wrote:
> From: zain wang <wzz@rock-chips.com>
> 
> It's too early to detect fast link training, if other step after it
> failed, we will set fast_link flag to 1, and retry set_bridge again. In
> this case we will power down and power up panel power supply, and we
> will do fast link training since we have set fast_link flag to 1. In
> fact, we should do full link training now, not the fast link training.
> So we should move the fast link detection at the end of set_bridge.
> 
> Cc: Tomasz Figa <tfiga@chromium.org>
> Signed-off-by: zain wang <wzz@rock-chips.com>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
> Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
> ---
>  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 42 +++++++++++++---------
>  1 file changed, 26 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index e7ab871e62b5..bee0f7aa5c23 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -599,7 +599,7 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
>  {
>  	int lane, lane_count, retval;
>  	u32 reg;
> -	u8 link_align, link_status[2], adjust_request[2], spread;
> +	u8 link_align, link_status[2], adjust_request[2];
>  
>  	usleep_range(400, 401);
>  
> @@ -643,20 +643,6 @@ static int analogix_dp_process_equalizer_training(struct analogix_dp_device *dp)
>  		dev_dbg(dp->dev, "final lane count = %.2x\n",
>  			dp->link_train.lane_count);
>  
> -		retval = drm_dp_dpcd_readb(&dp->aux, DP_MAX_DOWNSPREAD,
> -					   &spread);
> -		if (retval != 1) {
> -			dev_err(dp->dev, "failed to read downspread %d\n",
> -				retval);
> -			dp->fast_train_enable = false;
> -		} else {
> -			dp->fast_train_enable =
> -				(spread & DP_NO_AUX_HANDSHAKE_LINK_TRAINING) ?
> -					true : false;
> -		}
> -		dev_dbg(dp->dev, "fast link training %s\n",
> -			dp->fast_train_enable ? "supported" : "unsupported");
> -
>  		dp->link_train.lt_state = FINISHED;
>  
>  		return 0;
> @@ -997,6 +983,22 @@ static irqreturn_t analogix_dp_irq_thread(int irq, void *arg)
>  	return IRQ_HANDLED;
>  }
>  
> +static int analogix_dp_fast_link_train_detection(struct analogix_dp_device *dp)
> +{
> +	int ret;
> +	u8 spread;
> +
> +	ret = drm_dp_dpcd_readb(&dp->aux, DP_MAX_DOWNSPREAD, &spread);
> +	if (ret != 1) {
> +		dev_err(dp->dev, "failed to read downspread %d\n", ret);
> +		return ret;
> +	}
> +	dp->fast_train_enable = !!(spread & DP_NO_AUX_HANDSHAKE_LINK_TRAINING);
> +	dev_dbg(dp->dev, "fast link training %s\n",
> +		dp->fast_train_enable ? "supported" : "unsupported");
> +	return 0;
> +}
> +
>  static int analogix_dp_commit(struct analogix_dp_device *dp)
>  {
>  	int ret;
> @@ -1039,8 +1041,16 @@ static int analogix_dp_commit(struct analogix_dp_device *dp)
>  	if (ret)
>  		return ret;
>  
> -	if (dp->psr_enable)
> +	if (dp->psr_enable) {
>  		ret = analogix_dp_enable_sink_psr(dp);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/* Check whether panel supports fast training */
> +	ret =  analogix_dp_fast_link_train_detection(dp);
> +	if (ret)
> +		dp->psr_enable = false;

You could probably flip this with psr_enable and just return on error instead of
flipping psr_enable back. Not a big deal either way.

Sean

>  
>  	return ret;
>  }
> -- 
> 2.14.1
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS