Re: [PATCH v6 10/14] drm/panel: add S6E3FA0 driver

From: Thierry Reding <thierry.reding@gmail.com>
To: YoungJun Cho <yj44.cho@samsung.com>
Cc: mark.rutland@arm.com, devicetree@vger.kernel.org,
	linux-samsung-soc@vger.kernel.org, pawel.moll@arm.com,
	ijc+devicetree@hellion.org.uk,
	Tomi Valkeinen <tomi.valkeinen@ti.com>,
	Paul Mundt <paul.mundt@gmail.com>,
	sw0312.kim@samsung.com, dri-devel@lists.freedesktop.org,
	Andrzej Hajda <a.hajda@samsung.com>,
	kyungmin.park@samsung.com, robh+dt@kernel.org,
	galak@codeaurora.org, kgene.kim@samsung.com,
	Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Subject: Re: [PATCH v6 10/14] drm/panel: add S6E3FA0 driver
Date: Tue, 22 Jul 2014 09:49:36 +0200	[thread overview]
Message-ID: <20140722074935.GC18258@ulmo> (raw)
In-Reply-To: <53CDDD61.6000005@samsung.com>

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On Tue, Jul 22, 2014 at 12:41:21PM +0900, YoungJun Cho wrote:
> On 07/21/2014 08:18 PM, Andrzej Hajda wrote:
> >On 07/21/2014 11:19 AM, Thierry Reding wrote:
> >>On Mon, Jul 21, 2014 at 10:56:08AM +0200, Andrzej Hajda wrote:
> >>>On 07/18/2014 03:49 AM, YoungJun Cho wrote:
> >>>>On 07/17/2014 07:36 PM, Thierry Reding wrote:
> >>>>>On Thu, Jul 17, 2014 at 06:01:25PM +0900, YoungJun Cho wrote:
[...]
> >>>>>>+static void s6e3fa0_read_mtp_id(struct s6e3fa0 *ctx)
> >>>>>>+{
> >>>>>>+	unsigned char id[MTP_ID_LEN];
> >>>>>>+	int ret;
> >>>>>>+
> >>>>>>+	s6e3fa0_set_maximum_return_packet_size(ctx, MTP_ID_LEN);
> >>>>>>+	ret = s6e3fa0_dcs_read(ctx, MIPI_DCS_GET_DISPLAY_ID, id, MTP_ID_LEN);
> >>>>>This also looks like a standard DCS command. I can't find it in either
> >>>>>v1.01 nor v1.02 of the specification, though. Do you know where it's
> >>>>>specified?
> >>>>>
> >>>>Yes, I also can't find it in DCS specification and there is no special
> >>>>description in panel datasheet.
> >>>>But as it is declared in "include/video/mipi_display.h", so I think it
> >>>>is a standard one.
> >>>
> >>>On page 9 of the "Introduction of MIPI by Renesas" [2] there is info
> >>>it is a part of "Nokia I/F command list", I guess it is kind of alpha
> >>>version of MIPI DCS.
> >>>
> >>>[2]: http://wenku.baidu.com/view/658fab68af1ffc4ffe47acbe.html
> >>
> >>That link is the only one which contains "Nokia I/F command list" on the
> >>internet (that is, according to Google). But since this is already part
> >>of the mipi_display.h header file we may as well use it.
> >>
> >>I wonder if perhaps the READ_DDB_START and READ_DDB_CONTINUE commands
> >>could be used as a replacement for this display ID.
> >>
> 
> There is a simple description for "Read DDB Start(A1H)" like below.
> - This command returns supplier identification and display module model /
> revision information.
> - NOTE: This information is not the same what Read IDs(04H) command is
> returning.
> 
> For reference, Read IDs(04H) description is like below.
> - This read command returns 24-bit display identification information.
> - The first read byte identifies the OLED module's manufacturer.
> - The Second read byte is used to track the OLED module/driver version.
> - The third read byte identifies the OLED module/driver.

Okay, that explains things a little better. Can you point me to the
document that this is from?

But what I was trying to say is that if the Read IDs command isn't an
official DCS command, maybe it would be a better idea to use the DDB
instead. I assume that even if it isn't the same information it would
at least be a superset and therefore a suitable replacement.

Thierry

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