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

From: Yakir Yang <ykk@rock-chips.com>
To: Jingoo Han <jingoohan1@gmail.com>
Cc: Heiko Stuebner <heiko@sntech.de>,
	Thierry Reding <treding@nvidia.com>,
	Fabio Estevam <fabio.estevam@freescale.com>,
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Subject: Re: [PATCH v3 12/14] drm: bridge/analogix_dp: expand the delay time for hpd detect
Date: Thu, 20 Aug 2015 03:02:27 -0500	[thread overview]
Message-ID: <55D58993.4060502@rock-chips.com> (raw)
In-Reply-To: <A474A3AB-86A8-4967-B90F-31920A5E7BA3@gmail.com>

Hi Jingoo,

On 08/20/2015 01:11 AM, Jingoo Han wrote:
> On 2015. 8. 19., at PM 11:52, Yakir Yang <ykk@rock-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.

Yeah, you are right, I made an mistake here.

And I want to put this delay to "need-force-hpd" code, cause
this property is for the no-hpd-signal eDP screen.

But strangely, with my this series, I don't need the expand delay
any more, I am not sure which change improved this, I guess
those delay time should come from drm core ?

Whatever seems we don't need this delay for now, and if I can
find the exact reason and realize I still need this delay, I prefer
to add those delay in "need-force-hpd" code.

Thanks,
- Yakir
> Best regards,
> Jingoo Han
>
>> Signed-off-by: Yakir Yang <ykk@rock-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
>>
>>
>
>