Re: [PATCH v2] drm/i915/dsi: skip gpio element execution when not supported

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Feb 04, 2016 at 07:10:42PM +0200, Jani Nikula wrote:
> On Thu, 04 Feb 2016, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> > On Thu, Feb 04, 2016 at 06:52:47PM +0200, Jani Nikula wrote:
> >> Skip v3 gpio element because the support is not there, and skip gpio
> >> element on non-vlv because the sideband code is vlv specific.
> >> 
> >> v2: the gpio stuff is currently only supported on vlv (Ville)
> >> 
> >> Cc: drm-intel-fixes@lists.freedesktop.org
> >> Fixes: 2a33d93486f2 ("drm/i915/bios: add support for MIPI sequence block v3")
> >> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/intel_dsi_panel_vbt.c | 13 +++++++++++++
> >>  1 file changed, 13 insertions(+)
> >> 
> >> diff --git a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> >> index f4d303ee538b..bcc083db7632 100644
> >> --- a/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> >> +++ b/drivers/gpu/drm/i915/intel_dsi_panel_vbt.c
> >> @@ -205,6 +205,9 @@ static const u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, const u8 *data)
> >>  	struct drm_device *dev = intel_dsi->base.base.dev;
> >>  	struct drm_i915_private *dev_priv = dev->dev_private;
> >>  
> >> +	if (dev_priv->vbt.dsi.seq_version >= 3)
> >> +		data++;
> >> +
> >
> > So here we handle v3
> >
> >>  	gpio = *data++;
> >>  
> >>  	/* pull up/down */
> >> @@ -215,6 +218,16 @@ static const u8 *mipi_exec_gpio(struct intel_dsi *intel_dsi, const u8 *data)
> >>  		goto out;
> >>  	}
> >>  
> >> +	if (!IS_VALLEYVIEW(dev_priv)) {
> >> +		DRM_DEBUG_KMS("GPIO element not supported on this platform\n");
> >> +		goto out;
> >> +	}
> >> +
> >> +	if (dev_priv->vbt.dsi.seq_version >= 3) {
> >> +		DRM_DEBUG_KMS("GPIO element v3 not supported\n");
> >> +		goto out;
> >> +	}
> >
> > but here we say it's not supported. Is there more missing?
> 
> The whole point of doing it this way is to support *skipping* v3 in a
> graceful manner. If I bailed out at the top, I'd have to duplicate the
> knowledge about the length of the element.

Hmm, right. But the question still stands; what more is missing for
actual v3 support?

From what I saw in the spec, the new byte is there just for Windows.
Which in itself is an utter fail on part of the spec. There's no good
reason why Windows and Linux should do things differently because that
will probably mean putting Linux on some random machine that came with
Windows won't work :(

-- 
Ville Syrjälä
Intel OTC
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