[PATCH] drm/bridge: sii902x: Fall back to standard modes
Ville Syrjälä
ville.syrjala at linux.intel.com
Thu Mar 1 13:18:40 PST 2018
On Thu, Mar 01, 2018 at 10:02:55PM +0100, Linus Walleij wrote:
> Hm, hard to get review feedback on this one.
>
> It gives me proper video on an ARM Versatile Express utilizing the
> bridge driver with a plugged in DVI-to-VGA dongle with the new
> PL111 DRI driver.
>
> Liviu? Pawel?
>
> Some ACK is fine to know I am doing the right thing :)
Why isn't the probe helper's noedid fallback working?
>
> Yours,
> Linus Walleij
>
> On Wed, Feb 14, 2018 at 2:00 PM, Linus Walleij <linus.walleij at linaro.org> wrote:
> > The following happens when connection a DVI output driven
> > from the SiI9022 using a DVI-to-VGA adapter plug:
> >
> > i2c i2c-0: sendbytes: NAK bailout.
> > i2c i2c-0: sendbytes: NAK bailout.
> >
> > Then no picture. Apparently the I2C engine inside the SiI9022
> > is not smart enough to try to fall back to DDC I2C. Or the
> > vendor have not integrated the electronics properly. I don't
> > know which one it is.
> >
> > By using standard modes as fallback, the bridge probes nicely
> > with a minor warning and we get picture.
> >
> > This code is inspired by similar code in the dumb VGA bridge.
> >
> > Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> > ---
> > drivers/gpu/drm/bridge/sii902x.c | 15 +++++++++++++--
> > 1 file changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
> > index b1ab4ab09532..4483095c4013 100644
> > --- a/drivers/gpu/drm/bridge/sii902x.c
> > +++ b/drivers/gpu/drm/bridge/sii902x.c
> > @@ -168,8 +168,19 @@ static int sii902x_get_modes(struct drm_connector *connector)
> > return ret;
> >
> > edid = drm_get_edid(connector, sii902x->i2c->adapter);
> > - drm_mode_connector_update_edid_property(connector, edid);
> > - if (edid) {
> > + if (!edid) {
> > + /*
> > + * This happens when using a simple DVI-to-VGA converter
> > + * dongle for example: the I2C lines are not bridged over
> > + * to VGA DDC.
> > + */
> > + DRM_INFO("EDID readout failed, falling back to standard modes\n");
> > + ret = drm_add_modes_noedid(connector, 1920, 1080);
> > + /* Set some standard resolution most monitors can handle */
> > + drm_set_preferred_mode(connector, 1024, 768);
> > + } else {
> > + /* Data from EDID readout */
> > + drm_mode_connector_update_edid_property(connector, edid);
> > num = drm_add_edid_modes(connector, edid);
> > kfree(edid);
> > }
> > --
> > 2.14.3
> >
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> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel OTC
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