linux-kernel - Re: [PATCH v2 24/43] drm/bridge: analogix_dp: Reset aux channel if an error occurred

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Message-ID: <20180129212751.25eqa4s4aml52z6m@art_vandelay>
Date:   Mon, 29 Jan 2018 16:27:51 -0500
From:   Sean Paul <seanpaul@...omium.org>
To:     Thierry Escande <thierry.escande@...labora.com>
Cc:     Archit Taneja <architt@...eaurora.org>,
        Inki Dae <inki.dae@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Sandy Huang <hjc@...k-chips.com>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Tomasz Figa <tfiga@...omium.org>,
        Haixia Shi <hshi@...omium.org>,
        Ørjan Eide <orjan.eide@....com>,
        Zain Wang <wzz@...k-chips.com>,
        Yakir Yang <ykk@...k-chips.com>, Lin Huang <hl@...k-chips.com>,
        Douglas Anderson <dianders@...omium.org>,
        Mark Yao <mark.yao@...k-chips.com>,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 24/43] drm/bridge: analogix_dp: Reset aux channel if
 an error occurred

On Fri, Jan 26, 2018 at 02:16:51PM +0100, Thierry Escande wrote:
> From: Lin Huang <hl@...k-chips.com>
> 
> AUX errors are caused by many different reasons. We may not know what
> happened in aux channel on failure, so let's reset aux channel if some
> errors occurred.
> 
> Cc: 征增 王 <wzz@...k-chips.com>
> Cc: Douglas Anderson <dianders@...omium.org>
> Signed-off-by: Lin Huang <hl@...k-chips.com>
> Signed-off-by: Sean Paul <seanpaul@...omium.org>
> Signed-off-by: Thierry Escande <thierry.escande@...labora.com>
> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> ---
>  drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> index dee1ba109b5f..7b7fd227e1f9 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> @@ -466,6 +466,10 @@ void analogix_dp_init_aux(struct analogix_dp_device *dp)
>  	reg = RPLY_RECEIV | AUX_ERR;
>  	writel(reg, dp->reg_base + ANALOGIX_DP_INT_STA);
>  
> +	analogix_dp_set_analog_power_down(dp, AUX_BLOCK, true);
> +	usleep_range(10, 11);

This is kind of lame. I don't think this needs to be _exactly_ 10us, even 10/20 would be
an improvement. Since this is so infrequent, it's not a dealbreaker either way, I guess.

Sean

> +	analogix_dp_set_analog_power_down(dp, AUX_BLOCK, false);
> +
>  	analogix_dp_reset_aux(dp);
>  
>  	/* Disable AUX transaction H/W retry */
> @@ -1159,7 +1163,7 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  				 reg, !(reg & AUX_EN), 25, 500 * 1000);
>  	if (ret) {
>  		dev_err(dp->dev, "AUX CH enable timeout!\n");
> -		return -ETIMEDOUT;
> +		goto aux_error;
>  	}
>  
>  	/* TODO: Wait for an interrupt instead of looping? */
> @@ -1168,7 +1172,7 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  				 reg, reg & RPLY_RECEIV, 10, 20 * 1000);
>  	if (ret) {
>  		dev_err(dp->dev, "AUX CH cmd reply timeout!\n");
> -		return -ETIMEDOUT;
> +		goto aux_error;
>  	}
>  
>  	/* Clear interrupt source for AUX CH command reply */
> @@ -1178,7 +1182,7 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  	reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
>  	if (reg & AUX_ERR) {
>  		writel(AUX_ERR, dp->reg_base + ANALOGIX_DP_INT_STA);
> -		return -EREMOTEIO;
> +		goto aux_error;
>  	}
>  
>  	/* Check AUX CH error access status */
> @@ -1186,7 +1190,7 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  	if ((reg & AUX_STATUS_MASK)) {
>  		dev_err(dp->dev, "AUX CH error happened: %d\n\n",
>  			reg & AUX_STATUS_MASK);
> -		return -EREMOTEIO;
> +		goto aux_error;
>  	}
>  
>  	if (msg->request & DP_AUX_I2C_READ) {
> @@ -1212,4 +1216,10 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
>  		msg->reply = DP_AUX_NATIVE_REPLY_ACK;
>  
>  	return num_transferred > 0 ? num_transferred : -EBUSY;
> +
> +aux_error:
> +	/* if aux err happen, reset aux */
> +	analogix_dp_init_aux(dp);
> +
> +	return -EREMOTEIO;
>  }
> -- 
> 2.14.1
> 

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