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

[Nicolas Boichat <drinkcat@chromium.org>]

On Sun, Nov 13, 2022 at 8:29 AM Marek Vasut <marex@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.

Thanks,