Re: [PATCH 1/9] dt-bindings: mfd: Add bindings for SAM9X7 LCD controller

[Conor Dooley]

On Mon, Jun 26, 2023 at 05:31:59AM +0000, Manikandan.M@xxxxxxxxxxxxx wrote:
> On 21/06/23 13:17, Nicolas Ferre wrote:
> > On 16/06/2023 at 08:44, Manikandan M - I67131 wrote:
> >> On 14/06/23 20:10, Nicolas Ferre wrote:
> >>> On 13/06/2023 at 20:21, Conor Dooley wrote:
> >>>> On Tue, Jun 13, 2023 at 08:17:13PM +0200, Krzysztof Kozlowski wrote:
> >>>>> On 13/06/2023 09:04, Manikandan Muralidharan wrote:
> >>>>>> Add new compatible string for the XLCD controller on SAM9X7 SoC.
> >>>>>>
> >>>>>> Signed-off-by: Manikandan Muralidharan<manikandan.m@xxxxxxxxxxxxx>
> >>>>>> ---
> >>>>>>    Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt | 1 +
> >>>>>>    1 file changed, 1 insertion(+)
> >>>>>>
> >>>>>> diff --git a/Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt
> >>>>>> b/Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt
> >>>>>> index 5f8880cc757e..7c77b6bf4adb 100644
> >>>>>> --- a/Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt
> >>>>>> +++ b/Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt
> >>>>>> @@ -8,6 +8,7 @@ Required properties:
> >>>>>>       "atmel,sama5d3-hlcdc"
> >>>>>>       "atmel,sama5d4-hlcdc"
> >>>>>>       "microchip,sam9x60-hlcdc"
> >>>>>> +   "microchip,sam9x7-xlcdc"
> >>>>> Google says sam9x7 is a series, not a SoC. Please add compatibles for
> >>>>> specific SoCs, not for series.
> >>>> We had this one a few weeks ago, see
> >>>> https://lore.kernel.org/all/add5e49e-8416-ba9f-819a-da944938c05f@xxxxxxxxxxxxx/
> >>>> and its parents. Outcome of that seemed to be that using "sam9x7" was
> >>>> fine.
> >>>
> >>> And it's where it begins to be funny, as the LCD is precisely one aspect
> >>> where we differentiate between sam9x75, sam9x72 and sam9x70...
> >>> So please Manikandan sort this out if difference between these chips
> >>> will be better handled with different compatibility string, in
> >>> particular about //, LVDS and MIPI-DSI variants!
> >> Yes Sure, I will replace the compatible as s/sam9x7/sam9x75/g to handle
> >> the different variants of sam9x7 better.
> > 
> > Moving to sam9x75 is probably good. But what is your plan for 
> > differentiating parallel and LVDS (on sam9x72) and precisely this 
> > sam9x75 variant which in addition has MIPI-DSI?
> In sam9x75 with support for LVDS and MIPI, Parallel interfacing 
> peripherals, the additions performed on the LCD controller driver is the 
> same.Considering the LCDC IP used in sam9x75, there are no registers 
> sets that needs modification per connecting peripheral variants, only 
> the clock and DRM_ENCODER_MODE_XXX (set by connecting peripheral driver) 
> differs, which can be handled in DT, atmel-lcdc MFD driver and 
> peripheral driver.
> 
> In future, sam9x72 with XLCD controller can be differentiated with 
> sam9x72 compatible string and with a IP version flag(is_xlcdc_v2) in its 
> driver data if an upgraded XLCD IP is used with difference in bits or 
> register set exist compared to current IP.

Trying to covert that into what the binding will look like...
sam9x72 & sam9x75 each get their own compatibles for the lcd controller.
From there, we permit `compatible = "microchip,sam9x75-foo"` in
isolation. It *sounds* like the basic featureset of the sam9x75 is
compatible with the sam9x72, so for that we permit
`compatible = "microchip,sam9x72-foo", "microchip,sam9x75-foo"`.
Although, if the hardware for the sam9x72 isn't set in stone yet, it
might be best to hold off on documenting it until things settle down,
and only add the sam9x75 for now.

Cheers,
Conor.

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