Quoting Rodrigo Vivi (2018-01-02 19:12:18)
> On Sun, Dec 31, 2017 at 10:34:54PM +0000, Stefan Brüns wrote:
> > + edid = drm_get_edid(connector, i2c);
> > +
> > + if (!edid && !intel_gmbus_is_forced_bit(i2c)) {
> > + DRM_DEBUG_KMS("HDMI GMBUS EDID read failed, retry using GPIO
> > bit-banging\n");
> > + intel_gmbus_force_bit(i2c, true);
> > + edid = drm_get_edid(connector, i2c);
> > + intel_gmbus_force_bit(i2c, false);
> > + }
>
> Approach seems fine for this case.
> I just wonder what would be the risks of forcing this bit and edid read when
> nothing is present on the other end?
Should be no more risky than using GMBUS as the bit-banging is the
underlying HW protocol; it should just be adding an extra delay to
the disconnected probe. Offset against the chance that it fixes
detection of borderline devices.
I would say that given the explanation above, the question is why not
apply it universally? (Bonus points for including the explanation as
comments.)
-Chris
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