linux-kernel - Re: [PATCH v5 04/10] drm: bridge: samsung-dsim: complete the CLKLANE

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Message-ID: <CAOf5uwmcCA8hxeDv4dDPe1PRag2Gj_myHrGhuF7c2=-e=NPcfQ@mail.gmail.com>
Date:   Fri, 8 Dec 2023 09:34:41 +0100
From:   Michael Nazzareno Trimarchi <michael@...rulasolutions.com>
To:     Frieder Schrempf <frieder.schrempf@...tron.de>
Cc:     Dario Binacchi <dario.binacchi@...rulasolutions.com>,
        linux-kernel@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jonas Karlman <jonas@...boo.se>,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        dri-devel@...ts.freedesktop.org,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH v5 04/10] drm: bridge: samsung-dsim: complete the
 CLKLANE_STOP setting

Hi Frieder

On Thu, Dec 7, 2023 at 5:58 PM Frieder Schrempf
<frieder.schrempf@...tron.de> wrote:
>
> On 07.12.23 15:16, Dario Binacchi wrote:
> > The patch completes the setting of CLKLANE_STOP for the imx8mn and imx8mp
> > platforms (i. e. not exynos).
>
> This also affects i.MX8MM, so better just mention i.MX in general in the
> commit message.
>
> >
> > Co-developed-by: Michael Trimarchi <michael@...rulasolutions.com>
> > Signed-off-by: Michael Trimarchi <michael@...rulasolutions.com>
> > Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> > ---
> >
> > (no changes since v1)
> >
> >  drivers/gpu/drm/bridge/samsung-dsim.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> > index 15bf05b2bbe4..13f181c99d7e 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -96,6 +96,7 @@
> >  #define DSIM_MFLUSH_VS                       BIT(29)
> >  /* This flag is valid only for exynos3250/3472/5260/5430 */
> >  #define DSIM_CLKLANE_STOP            BIT(30)
> > +#define DSIM_NON_CONTINUOUS_CLKLANE  BIT(31)
> >
> >  /* DSIM_ESCMODE */
> >  #define DSIM_TX_TRIGGER_RST          BIT(4)
> > @@ -945,8 +946,12 @@ static int samsung_dsim_init_link(struct samsung_dsim *dsi)
> >        * power consumption.
> >        */
> >       if (driver_data->has_clklane_stop &&
> > -         dsi->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS)
> > +         dsi->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS) {
> > +             if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type))
> > +                     reg |= DSIM_NON_CONTINUOUS_CLKLANE;
> > +
> >               reg |= DSIM_CLKLANE_STOP;
> > +     }
>
> I really wonder what the difference between DSIM_NON_CONTINUOUS_CLKLANE
> and DSIM_CLKLANE_STOP is.
>
> If Exynos only has the latter, it's pretty clear what to use. But as
> i.MX has both of these bits, should both be set? Or is setting
> DSIM_NON_CONTINUOUS_CLKLANE enough and we should leave DSIM_CLKLANE_STOP
> alone?
>

We add the DSIM_NON_CONTINUOUS_CLKLANE because there was a similar
commit in NXP bsp.
Now according to the datasheet the DSIM_NON_CONTINUOUS_CLKLANE should
be the right bit.

NXP guys should clarify then a bit

Michael

> Maybe someone has a clue here. The description of the bits in the RM is:
>
> DSIM_NON_CONTINUOUS_CLKLANE - Non-continuous clock mode
> DSIM_CLKLANE_STOP -  PHY clock lane On/Off for ESD
>
> >       samsung_dsim_write(dsi, DSIM_CONFIG_REG, reg);
> >
> >       lanes_mask = BIT(dsi->lanes) - 1;