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Date: Tue, 08 Apr 2014 10:08:42 +0200
From: Denis Carikli <denis@eukrea.com>
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To: Andrzej Hajda <a.hajda@samsung.com>,
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Subject: Re: [PATCH v12][ 07/12] drm: drm_display_mode: add signal polarity
 flags
References: <1396874691-27954-1-git-send-email-denis@eukrea.com> <1396874691-27954-7-git-send-email-denis@eukrea.com> <534398D5.4090600@samsung.com>
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On 04/08/2014 08:36 AM, Andrzej Hajda wrote:
>
> Hi Denis,
Hi,

>> +#define DRM_MODE_FLAG_POL_PIXDATA_NEGEDGE	BIT(1)
>> +#define DRM_MODE_FLAG_POL_PIXDATA_POSEDGE	BIT(2)
>> +#define DRM_MODE_FLAG_POL_PIXDATA_PRESERVE	BIT(3)
>
> What is the purpose of DRM_MODE_FLAG_POL_PIXDATA_PRESERVE?
> If 'preserve' means 'ignore' we can set to zero negedge and posedge bits
> instead of adding new bit. If it is something different please describe it.
Yes, it meant 'ignore'.

The goal was to be able to have a way to keep the old behavior while 
still being able to set the flags.

So, with the imx-drm driver, if none of the DRM_MODE_FLAG_POL_PIXDATA 
were set(that is POSEDGE, NEGEDGE, PRESERVE), then in ipuv3-crtc.c, it 
went using the old flags settings that were previously hardcoded.

The same applied for DRM_MODE_FLAG_POL_DE.
The patch using theses flags is the 08/12 of this same serie.

>>   struct drm_display_mode {
[..]
>> +	unsigned int pol_flags;
>
> Adding field and macros description to the DocBook would be nice.
So I will have to describe it in the "Connector Helper Operations" 
section of drm.tmpl, right before the mode_valid synopsis ?

Denis.