[PATCH v8 01/14] drm: exynos: dsi: Fix MIPI_DSI*_NO_* mode flags

[Marek Vasut]

On 11/14/22 02:11, Nicolas Boichat wrote:
> On Sun, Nov 13, 2022 at 8:29 AM Marek Vasut <marex at denx.de> wrote:
>>
>> On 11/11/22 13:12, Nicolas Boichat wrote:
>>
>> [...]
>>
>>>>> BTW, are you sure DSIM_HSE_MODE is correct now?
>>>>
>>>> Yes, we have tested in imx8m platforms as well. Sébastien Szymanski
>>>> initially observed this issue on the imx8m platform.
>>>
>>> I'll repeat, are you sure about HSE specifically? You invert the
>>> polarity for HBP, HFP, and HSA, which makes sense given your patch
>>> 02/14.
>>>
>>> I'm concerned about HSE. Is the bit really a disable bit?
>>> MIPI_DSI_MODE_VIDEO_HSE is supposed to be an enable flag, so you
>>> should not do `reg |= DSIM_HSE_DISABLE;`, probably.
>>
>> I suspect the HSE bit is a misnomer, but its handling in the driver is
>> correct.
>>
>> i.MX 8M Plus Applications Processor Reference Manual, Rev. 1, 06/2021
>> Page 5436
>>
>> 23 HseDisableMode
>>
>> In Vsync pulse and Vporch area, MIPI DSI master transfers only Hsync
>> start packet to MIPI DSI slave at MIPI DSI spec 1.1r02. This bit
>> transfers Hsync end packet in Vsync pulse and Vporch area (optional).
>>
>> 0 = Disables transfer
>> 1 = Enables transfer
>>
>> In command mode, this bit is ignored.
> 
> Okay. I'd suggest adding a comment in the code, it'd be so tempting to
> attempt to "fix" this as the if/or pattern looks different from the
> others.
> 
> But it's up to you all.

I agree. Clearly the discrepancy is confusing and leads to mistakes.