[PATCH v6 06/18] video: tegra20: dc: add reset support

[Svyatoslav Ryhel]

пт, 19 квіт. 2024 р. о 19:05 Thierry Reding <thierry.reding at gmail.com> пише:
>
> On Tue Jan 23, 2024 at 6:16 PM CET, Svyatoslav Ryhel wrote:
> > Implement reset use to discard any changes which could have been
> > applied to DC before and can interfere with current configuration.
> >
> > Tested-by: Agneli <poczt at protonmail.ch> # Toshiba AC100 T20
> > Tested-by: Robert Eckelmann <longnoserob at gmail.com> # ASUS TF101
> > Tested-by: Andreas Westman Dorcsak <hedmoo at yahoo.com> # ASUS Grouper E1565
> > Tested-by: Ion Agorria <ion at agorria.com> # HTC One X
> > Tested-by: Svyatoslav Ryhel <clamor95 at gmail.com> # Nvidia Tegratab T114
> > Signed-off-by: Svyatoslav Ryhel <clamor95 at gmail.com>
> > ---
> >  drivers/video/tegra20/tegra-dc.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/video/tegra20/tegra-dc.c b/drivers/video/tegra20/tegra-dc.c
> > index 56a23b3c97..35abb6fe46 100644
> > --- a/drivers/video/tegra20/tegra-dc.c
> > +++ b/drivers/video/tegra20/tegra-dc.c
> > @@ -10,7 +10,9 @@
> >  #include <panel.h>
> >  #include <part.h>
> >  #include <pwm.h>
> > +#include <reset.h>
> >  #include <video.h>
> > +#include <linux/delay.h>
> >  #include <asm/cache.h>
> >  #include <asm/global_data.h>
> >  #include <asm/system.h>
> > @@ -342,6 +344,7 @@ static int tegra_lcd_probe(struct udevice *dev)
> >       struct video_uc_plat *plat = dev_get_uclass_plat(dev);
> >       struct video_priv *uc_priv = dev_get_uclass_priv(dev);
> >       struct tegra_lcd_priv *priv = dev_get_priv(dev);
> > +     struct reset_ctl reset_ctl;
> >       int ret;
> >
> >       /* Initialize the Tegra display controller */
> > @@ -349,6 +352,20 @@ static int tegra_lcd_probe(struct udevice *dev)
> >       funcmux_select(PERIPH_ID_DISP1, FUNCMUX_DEFAULT);
> >  #endif
> >
> > +     ret = reset_get_by_name(dev, "dc", &reset_ctl);
> > +     if (ret) {
> > +             log_err("reset_get_by_name() failed: %d\n", ret);
> > +             return ret;
> > +     }
> > +
> > +     clock_disable(priv->dc_clk[0]);
> > +
> > +     /* Reset everything set before */
> > +     reset_assert(&reset_ctl);
> > +     mdelay(4);
> > +     reset_deassert(&reset_ctl);
> > +     mdelay(4);
>
> Are you sure this works as intended? It's been a long time since I
> worked on this, but I seem to recall that most of these resets are
> actually synchronous, so in order for them to do what they're supposed
> to the clock needs to be kept running.
>
> The Linux driver certainly does this differently.

You have point, but I have tried to mostly adapt Linux tegra dc driver,
which has same logic in probe. Maybe I have not understood it properly.
Testing on T20, T30 and T114 passed without issues so far.

> Thierry