| Message ID | b541006fa0a1c34ac5f668dc561aa1598f8fd86c.1581682983.git-series.maxime@cerno.tech (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/sun4i: Support clock and data polarities on LVDS output | expand |
Hi Maxime. On Fri, Feb 14, 2020 at 01:24:38PM +0100, Maxime Ripard wrote: > Some LVDS encoders can change the polarity of the data signals being > sent. Add a DRM bus flag to reflect this. > > Signed-off-by: Maxime Ripard <maxime@cerno.tech> > --- > include/drm/drm_connector.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index 221910948b37..9a08fe6ab7c2 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -330,6 +330,8 @@ enum drm_panel_orientation { > * edge of the pixel clock > * @DRM_BUS_FLAG_SHARP_SIGNALS: Set if the Sharp-specific signals > * (SPL, CLS, PS, REV) must be used > + * @DRM_BUS_FLAG_DATA_LOW: The Data signals are active low > + * @DRM_BUS_FLAG_DATA_HIGH: The Data signals are active high Reading the description of these falgs always confuses me. In this case if neither bit 9 nor bit 10 is set then the data signals are netiher active low nor active high. So what can I then expect? We have the same logic loophole for DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE and DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE. So it is not new, but can we do better here? Sam > */ > enum drm_bus_flags { > DRM_BUS_FLAG_DE_LOW = BIT(0), > @@ -349,6 +351,8 @@ enum drm_bus_flags { > DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE = DRM_BUS_FLAG_SYNC_NEGEDGE, > DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE = DRM_BUS_FLAG_SYNC_POSEDGE, > DRM_BUS_FLAG_SHARP_SIGNALS = BIT(8), > + DRM_BUS_FLAG_DATA_LOW = BIT(9), > + DRM_BUS_FLAG_DATA_HIGH = BIT(10), > }; > > /** > -- > git-series 0.9.1
On Fri, Feb 14, 2020 at 05:13:59PM +0100, Sam Ravnborg wrote: > Hi Maxime. > > On Fri, Feb 14, 2020 at 01:24:38PM +0100, Maxime Ripard wrote: > > Some LVDS encoders can change the polarity of the data signals being > > sent. Add a DRM bus flag to reflect this. > > > > Signed-off-by: Maxime Ripard <maxime@cerno.tech> > > --- > > include/drm/drm_connector.h | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > index 221910948b37..9a08fe6ab7c2 100644 > > --- a/include/drm/drm_connector.h > > +++ b/include/drm/drm_connector.h > > @@ -330,6 +330,8 @@ enum drm_panel_orientation { > > * edge of the pixel clock > > * @DRM_BUS_FLAG_SHARP_SIGNALS: Set if the Sharp-specific signals > > * (SPL, CLS, PS, REV) must be used > > + * @DRM_BUS_FLAG_DATA_LOW: The Data signals are active low > > + * @DRM_BUS_FLAG_DATA_HIGH: The Data signals are active high > Reading the description of these falgs always confuses me. > In this case if neither bit 9 nor bit 10 is set then the data signals > are netiher active low nor active high. > So what can I then expect? > > We have the same logic loophole for DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE > and DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE. > So it is not new, but can we do better here? Honestly, I don't really get it either. I *think* this is to handle the sampling / output inversion properly which wouldn't be possible if this was only a bit set or not. Maxime
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index 221910948b37..9a08fe6ab7c2 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -330,6 +330,8 @@ enum drm_panel_orientation { * edge of the pixel clock * @DRM_BUS_FLAG_SHARP_SIGNALS: Set if the Sharp-specific signals * (SPL, CLS, PS, REV) must be used + * @DRM_BUS_FLAG_DATA_LOW: The Data signals are active low + * @DRM_BUS_FLAG_DATA_HIGH: The Data signals are active high */ enum drm_bus_flags { DRM_BUS_FLAG_DE_LOW = BIT(0), @@ -349,6 +351,8 @@ enum drm_bus_flags { DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE = DRM_BUS_FLAG_SYNC_NEGEDGE, DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE = DRM_BUS_FLAG_SYNC_POSEDGE, DRM_BUS_FLAG_SHARP_SIGNALS = BIT(8), + DRM_BUS_FLAG_DATA_LOW = BIT(9), + DRM_BUS_FLAG_DATA_HIGH = BIT(10), }; /**
Some LVDS encoders can change the polarity of the data signals being sent. Add a DRM bus flag to reflect this. Signed-off-by: Maxime Ripard <maxime@cerno.tech> --- include/drm/drm_connector.h | 4 ++++ 1 file changed, 4 insertions(+)