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

[Andrzej Hajda <a.hajda@samsung.com>]

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:
>>> Hi Thierry,
>>>
>>> Thank you a lot for kind comments.
>>>
>>> On 07/17/2014 07:36 PM, Thierry Reding wrote:
>>>> On Thu, Jul 17, 2014 at 06:01:25PM +0900, YoungJun Cho wrote:
>>>> [...]
>>>>> diff --git a/drivers/gpu/drm/panel/panel-s6e3fa0.c b/drivers/gpu/drm/panel/panel-s6e3fa0.c
>>>> [...]
>>>>> +/* Manufacturer Command Set */
>>>>> +#define MCS_GLOBAL_PARAMETER	0xb0
>>>>> +#define MCS_AID			0xb2
>>>>> +#define MCS_ELVSSOPT		0xb6
>>>>> +#define MCS_TEMPERATURE_SET	0xb8
>>>>> +#define MCS_PENTILE_CTRL	0xc0
>>>>> +#define MCS_GAMMA_MODE		0xca
>>>>> +#define MCS_VDDM		0xd7
>>>>> +#define MCS_ALS			0xe3
>>>>> +#define MCS_ERR_FG		0xed
>>>>> +#define MCS_KEY_LEV1		0xf0
>>>>> +#define MCS_GAMMA_UPDATE	0xf7
>>>>> +#define MCS_KEY_LEV2		0xfc
>>>>> +#define MCS_RE			0xfe
>>>>> +#define MCS_TOUT2_HSYNC		0xff
>>>>> +
>>>>> +/* Content Adaptive Brightness Control */
>>>>> +#define DCS_WRITE_CABC		0x55
>>>> Is this not a manufacturer specific command? I couldn't find it in the
>>>> DSI or DCS specifications, but it sounds like something standard (also
>>>> indicated by the DCS_ prefix). Can you point out the specification for
>>>> this?
>>>>
>>> Andrzej commented before and decided it as DCS one because if the value 
>>> is less than 0xb0, it is DCS one and the others are MCS one.
>>> But still I'm not sure it is correct.
>> I would not say 'decided'. I have just stated that according to DCS
>> specification
>> it should be DCS command (below 0xb0), but it is not present in mipi dcs
>> specs.
>> On the other side many panels have it [1]:
>>
>> [1]:
>> https://www.google.com/search?q=%22Write+Content+Adaptive+Brightness+Control%22
> 
> Yeah, my search yielded similar results. I wonder if this is perhaps
> part of a draft future specification. I'll try to ask around some more
> if anybody knows what the status of this is.
> 
>>>>> +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.
> 
> Adding Guennadi, Tomi, Paul and Imre on Cc since they were involved with
> the original patch that added mipi_display.h. Perhaps they remember what
> the origin of this command is.


I guess it was PCF8833 used in Nokia 6100 [1][2].

[1]: http://www.vintagecomputercables.com/datasheet/PCF8833_1.pdf
[2]:
http://www.elecfreaks.com/store/download/datasheet/shield/6100_Display_Driver.pdf

Regards
Andrzej

> 
> Thierry
>