linux-kernel - Re: [PATCH v3 12/14] drm: bridge/analogix_dp: expand the delay time for hpd detect

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Message-Id: <A474A3AB-86A8-4967-B90F-31920A5E7BA3@gmail.com>
Date:	Thu, 20 Aug 2015 15:11:29 +0900
From:	Jingoo Han <jingoohan1@...il.com>
To:	Yakir Yang <ykk@...k-chips.com>
Cc:	Heiko Stuebner <heiko@...ech.de>,
	Thierry Reding <treding@...dia.com>,
	Fabio Estevam <fabio.estevam@...escale.com>,
	Inki Dae <inki.dae@...sung.com>,
	"joe@...ches.com" <joe@...ches.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	"djkurtz@...gle.com" <djkurtz@...gle.com>,
	"dianders@...gle.com" <dianders@...gle.com>,
	"seanpaul@...gle.com" <seanpaul@...gle.com>,
	Takashi Iwai <tiwai@...e.de>,
	"ajaynumb@...il.com" <ajaynumb@...il.com>,
	Andrzej Hajda <a.hajda@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	David Airlie <airlied@...ux.ie>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	Vincent Palatin <vpalatin@...omium.org>,
	Mark Yao <mark.yao@...k-chips.com>,
	Andy Yan <andy.yan@...k-chips.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Kishon Vijay Abraham I <kishon@...com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-rockchip@...ts.infradead.org" 
	<linux-rockchip@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, jingoohan1@...il.com
Subject: Re: [PATCH v3 12/14] drm: bridge/analogix_dp: expand the delay time for hpd detect

On 2015. 8. 19., at PM 11:52, Yakir Yang <ykk@...k-chips.com> wrote:
> 
> Some edp screen with no hpd signal would need some delay time
> to ensure that screen would be ready for work, so we can expand
> the delay time in hpd detect function, it works prefectly on my
> rk3288 sdk board.

Then, this delay has a dependency on the "rk3288 sdk" board.
Also, if the delay time is expanded, the booting time of some Exybos boards will be increased unnecessarily. :-(

So, please add new DT property such as 'hpd-delay' that can be added to board DT files.

If there is not that DT property in DT files, the default value '10' will written to a variable such as 'unsigned int hpd_delay'.
If there is the DT property in DT files, the delay value will written to the variable when parsing DT values
and will be used in analogix_dp_detect_hpd().

What I want to say is that there should not be harmful effect on the existing Exynos boards, due to unrelated reasons.

Best regards,
Jingoo Han

> Signed-off-by: Yakir Yang <ykk@...k-chips.com>
> ---
> Changes in v3: None
> Changes in v2: None
> 
> drivers/gpu/drm/bridge/analogix_dp_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix_dp_core.c
> index 99870f7..75dd44a 100644
> --- a/drivers/gpu/drm/bridge/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix_dp_core.c
> @@ -68,7 +68,7 @@ static int analogix_dp_detect_hpd(struct analogix_dp_device *dp)
>            return 0;
> 
>        timeout_loop++;
> -        usleep_range(10, 11);
> +        usleep_range(100, 110);
>    }
> 
>    /*
> -- 
> 1.9.1
> 
> 
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