Re: [PATCH 1/2] drm/bridge/lontium-lt9611uxc: fix waiting for EDID to become available

From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Vinod Koul <vkoul@kernel.org>, Sam Ravnborg <sam@ravnborg.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Subject: Re: [PATCH 1/2] drm/bridge/lontium-lt9611uxc: fix waiting for EDID to become available
Date: Thu, 14 Jan 2021 21:49:02 -0600	[thread overview]
Message-ID: <YAEQrnlHA+Z8YTij@builder.lan> (raw)
In-Reply-To: <20201127092316.122246-1-dmitry.baryshkov@linaro.org>

On Fri 27 Nov 03:23 CST 2020, Dmitry Baryshkov wrote:

> - Call wake_up() when EDID ready event is received to wake
>   wait_event_interruptible_timeout()
> 
> - Increase waiting timeout, reading EDID can take longer than 100ms, so
>   let's be on a safe side.
> 
> - Return NULL pointer from get_edid() callback rather than ERR_PTR()
>   pointer, as DRM code does NULL checks rather than IS_ERR().
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/gpu/drm/bridge/lontium-lt9611uxc.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> index 0c98d27f84ac..b708700e182d 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> @@ -145,8 +145,10 @@ static irqreturn_t lt9611uxc_irq_thread_handler(int irq, void *dev_id)
>  
>  	lt9611uxc_unlock(lt9611uxc);
>  
> -	if (irq_status & BIT(0))
> +	if (irq_status & BIT(0)) {
>  		lt9611uxc->edid_read = !!(hpd_status & BIT(0));
> +		wake_up_all(&lt9611uxc->wq);

This seems like a really good idea :)

> +	}
>  
>  	if (irq_status & BIT(1)) {
>  		if (lt9611uxc->connector.dev)
> @@ -465,7 +467,7 @@ static enum drm_connector_status lt9611uxc_bridge_detect(struct drm_bridge *brid
>  static int lt9611uxc_wait_for_edid(struct lt9611uxc *lt9611uxc)
>  {
>  	return wait_event_interruptible_timeout(lt9611uxc->wq, lt9611uxc->edid_read,
> -			msecs_to_jiffies(100));
> +			msecs_to_jiffies(500));
>  }
>  
>  static int lt9611uxc_get_edid_block(void *data, u8 *buf, unsigned int block, size_t len)
> @@ -503,7 +505,10 @@ static struct edid *lt9611uxc_bridge_get_edid(struct drm_bridge *bridge,
>  	ret = lt9611uxc_wait_for_edid(lt9611uxc);
>  	if (ret < 0) {
>  		dev_err(lt9611uxc->dev, "wait for EDID failed: %d\n", ret);
> -		return ERR_PTR(ret);
> +		return NULL;
> +	} else if (ret == 0) {
> +		dev_err(lt9611uxc->dev, "wait for EDID timeout\n");
> +		return NULL;

This looks like it should be a separate patch.

Regards,
Bjorn

>  	}
>  
>  	return drm_do_get_edid(connector, lt9611uxc_get_edid_block, lt9611uxc);
> -- 
> 2.29.2
> 