[PATCH 1/9] dt-bindings: mxsfb: Add compatible for i.MX8MP

[Marek Vasut]

On 2/28/22 07:37, Liu Ying wrote:
> Hi Marek,

Hi,

> On Mon, 2022-02-28 at 01:45 +0100, Marek Vasut wrote:
>> Add compatible string for i.MX8MP LCDIF variant. This is called LCDIFv3
>> and is completely different from the LCDIFv3 found in i.MX23 in that it
> 
> In i.MX23 reference manual, there is no LCDIFv3 found, but only LCDIF.

See i.MX23 HW_LCDIF_VERSION MAJOR=0x3 , that's LCDIF V3 . MX28 has LCDIF 
V4 .

>> has a completely scrambled register layout compared to all previous LCDIF
> 
> It looks like no single register of i.MX8MP LCDIFv3 overlaps with
> registers in other i.MX2x/6x/7x/8x LCDIFs. The LCDIFv3 block diagram is
> totally different from the LCDIF block diagram, according to the SoC
> reference manuals. LCDIFv3 supports SHADOW_EN bit to update horizontal
> and vertical size of graphic, position of graphic on the panel, address
> of graphic in memory and color formats or color palettes, which is not
> supported by LCDIF and impacts display driver control mechanism
> considerably. LCDIF supports DOTCLK interface, MPU interface and VSYNC
> interface, while LCDIFv3 only supports parallel output as a counterpart
> of the DOTCLK interface.
> 
> Generally speaking, LCDIFv3 is just a new display IP which happens to
> have the word 'LCDIF' in its name.  Although both of LCDIFv3 and LCDIF
> are display controllers for scanning out frames onto display devices, I
> don't think they are in one family.
> 
> So, LCDIFv3 deserves a new separate dt-binding, IMO.

It seems to me a lot of those bits just map to their previous 
equivalents in older LCDIF, others were dropped, so this is some sort of 
new LCDIF mutation, is it not ?

I am aware NXP has a separate driver in its downstream, but I'm not 
convinced the duplication of boilerplate code by introducing a separate 
driver for what looks like another LCDIF variant is the right approach.

>> variants. The new LCDIFv3 also supports 36bit address space. However,
>> except for the complete bit reshuffling, this is still LCDIF and it still
>> works like one.

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