Re: [PATCH v2 04/12] drm/sun4i: sun6i_mipi_dsi: Simplify drq set to support all modes

[Jagan Teki <jagan@amarulasolutions.com>]

On Tue, Nov 20, 2018 at 8:02 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
>
> On Mon, Nov 19, 2018 at 04:52:17PM +0530, Jagan Teki wrote:
> > On Mon, Nov 19, 2018 at 2:02 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> > >
> > > On Fri, Nov 16, 2018 at 10:09:08PM +0530, Jagan Teki wrote:
> > > > Allwinner MIPI DSI DRQ set value can be varied with respective
> > > > video modes.
> > > > - burst mode the set value is always 0
> > > > - video modes whose front porch greater than 20, the set value
> > > >   can be computed based front porch and bpp.
> > > > - video modes whose front porch is not greater than 20, the set value
> > > >   is simply 0
> > > >
> > > > This patch simplifies existing drq set value code by grouping
> > > > into sun6i_dsi_get_drq and support all video modes.
> > > >
> > > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > > > ---
> > > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 38 ++++++++++++++++----------
> > > >  1 file changed, 23 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > index efd08bfd0cb8..d60955880c43 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > @@ -363,6 +363,26 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
> > > >                    SUN6I_DSI_INST_JUMP_CFG_NUM(1));
> > > >  };
> > > >
> > > > +static int sun6i_dsi_get_drq(struct sun6i_dsi *dsi,
> > > > +                           struct drm_display_mode *mode)
> > > > +{
> > > > +     struct mipi_dsi_device *device = dsi->device;
> > > > +     int drq = 0;
> > >
> > > So, here, you declaring a variable called drq, set to 0.
> > >
> > > > +     if (device->mode_flags & MIPI_DSI_MODE_VIDEO_BURST)
> > > > +             return drq;
> > >
> > > That you return here. You could just return 0, to be clearer.
> > >
> > > > +     if ((mode->hsync_start - mode->hdisplay) > 20) {
> > > > +             /* Maaaaaagic */
> > > > +             u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
> > >
> > > You re-declare a variable with the same name here, but a different
> > > type....
> > >
> > > > +             drq *= mipi_dsi_pixel_format_to_bpp(device->format);
> > > > +             drq /= 32;
> > > > +     }
> > > > +
> > > > +     return drq;
> > >
> > > And then return the first one? How is that even working?
> >
> > Will fix this.
>
> I don't want you to only fix this, I also want you to contribute code
> that is A) useful, B) tested.

It was tested in burst mode panel, the same added in the series. It
worked because burst mode need 0 drq rate.

>
> > > >  static u16 sun6i_dsi_get_timings_vblk(struct sun6i_dsi *dsi,
> > > >                                     struct drm_display_mode *mode, u16 hblk)
> > > >  {
> > > > @@ -478,21 +498,9 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
> > > >  static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
> > > >                                 struct drm_display_mode *mode)
> > > >  {
> > > > -     struct mipi_dsi_device *device = dsi->device;
> > > > -     u32 val = 0;
> > > > -
> > > > -     if ((mode->hsync_start - mode->hdisplay) > 20) {
> > > > -             /* Maaaaaagic */
> > > > -             u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
> > > > -
> > > > -             drq *= mipi_dsi_pixel_format_to_bpp(device->format);
> > > > -             drq /= 32;
> > > > -
> > > > -             val = (SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
> > > > -                    SUN6I_DSI_TCON_DRQ_SET(drq));
> > > > -     }
> > > > -
> > > > -     regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG, val);
> > > > +     regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG,
> > > > +                  SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
> > > > +                  SUN6I_DSI_TCON_DRQ_SET(sun6i_dsi_get_drq(dsi, mode)));
> > >
> > > On top of that, you now enable the DRQ stuff all the time, while it
> >
> > Earlier the val value is ENABLE_MODE ORed with drq value. for the
> > condition drq is computed in if block otherwise the val is 0.
> > So as I explained in commit message the drq value is 0
> > - for video modes whose front porch is not greater than 20 and
> > - for burst mode the val
> >
> > ie reason I mode it common.
>
> The previous code was enabling it if the front porch was larger than
> 20 only. You enable it all the time now, and you never explain why.

Got it. Loo like I was confused to test these two separate series in
separate panels and missed something. Is it Ok to combine all dsi
changes together and send it in next version.