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Subject[PATCH 4/9] drm/panel: simple: add support for overriding the pixel clock polarity
Date
The Ka-Ro electronics MB7 baseboard has an on-board LCD->LVDS
converter that requires a fixed pixelclk polarity, no matter what the
panel's display_mode specifies. Add an option to override the pixelclk
polarity defined in the panel's display_mode via DTB.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
---
.../bindings/display/panel/simple-panel.txt | 3 +++
drivers/gpu/drm/panel/panel-simple.c | 30 ++++++++++++++++++++++
2 files changed, 33 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/simple-panel.txt b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
index e2308c3..dcaf9a7 100644
--- a/Documentation/devicetree/bindings/display/panel/simple-panel.txt
+++ b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
@@ -9,6 +9,9 @@ Optional properties:
- backlight: phandle of the backlight device attached to the panel
- bus-format-override: override the bus_format setting of the panel's
display_mode settings
+- pixelclk-active: override the pixelclock polarity defined in the
+ panel's display_mode settings
+

Example:

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index f356a7b..7bbb752 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -89,6 +89,12 @@ struct panel_simple {
struct gpio_desc *enable_gpio;

u32 bus_fmt_override;
+ u32 quirks;
+};
+
+enum {
+ PANEL_QUIRK_PIXDATA_NEGEDGE = BIT(0),
+ PANEL_QUIRK_PIXDATA_POSEDGE = BIT(1),
};

#define SP_DISPLAY_MODE(freq, ha, hfp, hs, hbp, va, vfp, vs, vbp, vr, flgs) { \
@@ -110,6 +116,15 @@ static inline struct panel_simple *to_panel_simple(struct drm_panel *panel)
return container_of(panel, struct panel_simple, base);
}

+static inline void panel_simple_apply_quirks(struct panel_simple *panel,
+ struct drm_display_info *info)
+{
+ if (panel->quirks & PANEL_QUIRK_PIXDATA_NEGEDGE)
+ info->bus_flags |= DRM_BUS_FLAG_PIXDATA_NEGEDGE;
+ if (panel->quirks & PANEL_QUIRK_PIXDATA_POSEDGE)
+ info->bus_flags |= DRM_BUS_FLAG_PIXDATA_POSEDGE;
+}
+
static int panel_simple_get_fixed_modes(struct panel_simple *panel)
{
struct drm_connector *connector = panel->base.connector;
@@ -175,6 +190,8 @@ static int panel_simple_get_fixed_modes(struct panel_simple *panel)
drm_display_info_set_bus_formats(&connector->display_info,
&panel->desc->bus_format, 1);
connector->display_info.bus_flags = panel->desc->bus_flags;
+ if (panel->quirks)
+ panel_simple_apply_quirks(panel, &connector->display_info);

return num;
}
@@ -308,6 +325,7 @@ static inline int panel_simple_check_quirks(struct device *dev,
struct panel_simple *p)
{
const char *bus_fmt;
+ u32 clkpol;

if (of_property_read_string(dev->of_node, "bus-format-override",
&bus_fmt) == 0) {
@@ -329,6 +347,18 @@ static inline int panel_simple_check_quirks(struct device *dev,
bus_fmt);
return p->bus_fmt_override ? 0 : -EINVAL;
}
+
+ if (of_property_read_u32(dev->of_node, "pixelclk-active",
+ &clkpol) == 0) {
+ if (clkpol & ~1) {
+ dev_err(dev,
+ "Invalid value for pixelclk-active: '%u' (should be <0> or <1>)\n",
+ clkpol);
+ return -EINVAL;
+ }
+ p->quirks |= clkpol ? PANEL_QUIRK_PIXDATA_POSEDGE :
+ PANEL_QUIRK_PIXDATA_NEGEDGE;
+ }
return 0;
}

--
2.1.4
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