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From: Doug Anderson <dianders@google.com>
Date: Tue, 23 Apr 2024 13:41:59 -0700
Message-ID: <CAD=FV=VYAzqsGEBJai9b9n+HxHiG59L1vF73AEWcTwLS_ryjWw@mail.gmail.com>
Subject: Re: [PATCH v1 2/2] drm/panel: kd101ne3: add new panel driver
To: Hsin-Yi Wang <hsinyi@google.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>, 
	lvzhaoxiong <lvzhaoxiong@huaqin.corp-partner.google.com>, mripard@kernel.org, 
	airlied@gmail.com, daniel@ffwll.ch, robh@kernel.org, 
	krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, 
	dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, 
	linux-kernel@vger.kernel.org, 
	cong yang <yangcong5@huaqin.corp-partner.google.com>
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Hi,

On Tue, Apr 23, 2024 at 11:10=E2=80=AFAM Hsin-Yi Wang <hsinyi@google.com> w=
rote:
>
> > > > > +#define _INIT_DCS_CMD(...) { \
> > > > > +     .type =3D INIT_DCS_CMD, \
> > > > > +     .len =3D sizeof((char[]){__VA_ARGS__}), \
> > > > > +     .data =3D (char[]){__VA_ARGS__} }
> > > > > +
> > > > > +#define _INIT_DELAY_CMD(...) { \
> > > > > +     .type =3D DELAY_CMD,\
> > > > > +     .len =3D sizeof((char[]){__VA_ARGS__}), \
> > > > > +     .data =3D (char[]){__VA_ARGS__} }
> > > >
> > > > This is the third panel driver using the same appoach. Can you use
> > > > mipi_dsi_generic_write_seq() instead of the huge table? Or if you p=
refer
> > > > the table, we should extract this framework to a common helper.
> > > > (my preference is shifted towards mipi_dsi_generic_write_seq()).
> > > >
> > > The drawback of mipi_dsi_generic_write_seq() is that it can cause the
> > > kernel size grows a lot since every sequence will be expanded.
> > >
> > > Similar discussion in here:
> > > https://lore.kernel.org/dri-devel/CAD=3DFV=3DWju3WS45=3DEpXMUg7FjYDh3=
-=3Dmvm_jS7TF1tsaAzbb4Uw@mail.gmail.com/
> > >
> > > This patch would increase the module size from 157K to 572K.
> > > scripts/bloat-o-meter shows chg +235.95%.
> > >
> > > So maybe the common helper is better regarding the kernel module size=
?
> >
> > Yes, let's get a framework done in a useful way.
> > I'd say, drop the _INIT_DELAY_CMD. msleep() and usleep_range() should b=
e
> > used instead (and it's up to the developer to select correct delay
> > function).
> >
> > >
> > > > > +
> > > > > +static const struct panel_init_cmd kingdisplay_kd101ne3_init_cmd=
[] =3D {
> > > > > +     _INIT_DELAY_CMD(50),
> > > > > +     _INIT_DCS_CMD(0xE0, 0x00),
> >
> > [skipped the body of the table]
> >
> > > > > +     _INIT_DCS_CMD(0x0E, 0x48),
> > > > > +
> > > > > +     _INIT_DCS_CMD(0xE0, 0x00),
> >
> > > > > +     _INIT_DCS_CMD(0X11),
> >
> > Also, at least this is mipi_dsi_dcs_exit_sleep_mode().
> >
> > > > > +     /* T6: 120ms */
> > > > > +     _INIT_DELAY_CMD(120),
> > > > > +     _INIT_DCS_CMD(0X29),
> >
> > And this is mipi_dsi_dcs_set_display_on().
> >
> > Having a single table enourages people to put known commands into the
> > table, the practice that must be frowned upon and forbidden.
> >
> > We have functions for some of the standard DCS commands. So, maybe
> > instead of adding a single-table based approach we can improve
> > mipi_dsi_generic_write_seq() to reduce the bloat. E.g. by moving the
> > error handling to a common part of enable() / prepare() function.
> >
>
> For this panel, I think it can also refer to how
> panel-kingdisplay-kd097d04.c does. Create the table for init cmd data,
> not what operation to use, and use mipi_dsi_generic_write_seq() when
> looping through the table.

Even more similar discussion:

https://lore.kernel.org/r/CAD=3DFV=3DUGDbNvAMjzWSOvxybGikQcvW9JsRtbxHVg8_97=
YPEQCA@mail.gmail.com