video: add display_timing and videomode

Add display_timing structure and the according helper functions. This allows
the description of a display via its supported timing parameters.

Also, add helper functions to convert from display timings to a generic videomode
structure.

The struct display_timing specifies all needed parameters to describe the signal
properties of a display in one mode. This includes
    - ranges for signals that may have min-, max- and typical values
    - single integers for signals that can be on, off or are ignored
    - booleans for signals that are either on or off

As a display may support multiple modes like this, a struct display_timings is
added, that holds all given struct display_timing pointers and declares the
native mode of the display.

Although a display may state that a signal can be in a range, it is driven with
fixed values that indicate a videomode. Therefore graphic drivers don't need all
the information of struct display_timing, but would generate a videomode from
the given set of supported signal timings and work with that.

The video subsystems all define their own structs that describe a mode and work
with that (e.g. fb_videomode or drm_display_mode). To slowly replace all those
various structures and allow code reuse across those subsystems, add struct
videomode as a generic description.

This patch only includes the most basic fields in struct videomode. All missing
fields that are needed to have a really generic video mode description can be
added at a later stage.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Reviewed-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Thierry Reding <thierry.reding@avionic-design.de>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Afzal Mohammed <Afzal@ti.com>
Tested-by: Rob Clark <robclark@gmail.com>
Tested-by: Leela Krishna Amudala <leelakrishna.a@gmail.com>

2 files changed, 172 insertions, 0 deletions

diff --git a/include/video/display_timing.h b/include/video/display_timing.h
new file mode 100644
index 000000000000..71e9a383a981
--- /dev/null
+++ b/include/video/display_timing.h
@@ -0,0 +1,124 @@
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ *
+ * description of display timings
+ *
+ * This file is released under the GPLv2
+ */
+
+#ifndef __LINUX_DISPLAY_TIMING_H
+#define __LINUX_DISPLAY_TIMING_H
+
+#include <linux/bitops.h>
+#include <linux/types.h>
+
+/* VESA display monitor timing parameters */
+#define VESA_DMT_HSYNC_LOW              BIT(0)
+#define VESA_DMT_HSYNC_HIGH             BIT(1)
+#define VESA_DMT_VSYNC_LOW              BIT(2)
+#define VESA_DMT_VSYNC_HIGH             BIT(3)
+
+/* display specific flags */
+#define DISPLAY_FLAGS_DE_LOW            BIT(0)  /* data enable flag */
+#define DISPLAY_FLAGS_DE_HIGH           BIT(1)
+#define DISPLAY_FLAGS_PIXDATA_POSEDGE   BIT(2)  /* drive data on pos. edge */
+#define DISPLAY_FLAGS_PIXDATA_NEGEDGE   BIT(3)  /* drive data on neg. edge */
+#define DISPLAY_FLAGS_INTERLACED        BIT(4)
+#define DISPLAY_FLAGS_DOUBLESCAN        BIT(5)
+
+/*
+ * A single signal can be specified via a range of minimal and maximal values
+ * with a typical value, that lies somewhere inbetween.
+ */
+struct timing_entry {
+        u32 min;
+        u32 typ;
+        u32 max;
+};
+
+enum timing_entry_index {
+        TE_MIN = 0,
+        TE_TYP = 1,
+        TE_MAX = 2,
+};
+
+/*
+ * Single "mode" entry. This describes one set of signal timings a display can
+ * have in one setting. This struct can later be converted to struct videomode
+ * (see include/video/videomode.h). As each timing_entry can be defined as a
+ * range, one struct display_timing may become multiple struct videomodes.
+ *
+ * Example: hsync active high, vsync active low
+ *
+ *                                  Active Video
+ * Video  ______________________XXXXXXXXXXXXXXXXXXXXXX_____________________
+ *        |<- sync ->|<- back ->|<----- active ----->|<- front ->|<- sync..
+ *        |          |   porch  |                    |   porch   |
+ *
+ * HSync _|¯¯¯¯¯¯¯¯¯¯|___________________________________________|¯¯¯¯¯¯¯¯¯
+ *
+ * VSync ¯|__________|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|_________
+ */
+struct display_timing {
+        struct timing_entry pixelclock;
+
+        struct timing_entry hactive;            /* hor. active video */
+        struct timing_entry hfront_porch;       /* hor. front porch */
+        struct timing_entry hback_porch;        /* hor. back porch */
+        struct timing_entry hsync_len;          /* hor. sync len */
+
+        struct timing_entry vactive;            /* ver. active video */
+        struct timing_entry vfront_porch;       /* ver. front porch */
+        struct timing_entry vback_porch;        /* ver. back porch */
+        struct timing_entry vsync_len;          /* ver. sync len */
+
+        unsigned int dmt_flags;                 /* VESA DMT flags */
+        unsigned int data_flags;                /* video data flags */
+};
+
+/*
+ * This describes all timing settings a display provides.
+ * The native_mode is the default setting for this display.
+ * Drivers that can handle multiple videomodes should work with this struct and
+ * convert each entry to the desired end result.
+ */
+struct display_timings {
+        unsigned int num_timings;
+        unsigned int native_mode;
+
+        struct display_timing **timings;
+};
+
+/* get value specified by index from struct timing_entry */
+static inline u32 display_timing_get_value(const struct timing_entry *te,
+                                           enum timing_entry_index index)
+{
+        switch (index) {
+        case TE_MIN:
+                return te->min;
+                break;
+        case TE_TYP:
+                return te->typ;
+                break;
+        case TE_MAX:
+                return te->max;
+                break;
+        default:
+                return te->typ;
+        }
+}
+
+/* get one entry from struct display_timings */
+static inline struct display_timing *display_timings_get(const struct
+                                                         display_timings *disp,
+                                                         unsigned int index)
+{
+        if (disp->num_timings > index)
+                return disp->timings[index];
+        else
+                return NULL;
+}
+
+void display_timings_release(struct display_timings *disp);
+
+#endif
diff --git a/include/video/videomode.h b/include/video/videomode.h
new file mode 100644
index 000000000000..a42156234dd4
--- /dev/null
+++ b/include/video/videomode.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ *
+ * generic videomode description
+ *
+ * This file is released under the GPLv2
+ */
+
+#ifndef __LINUX_VIDEOMODE_H
+#define __LINUX_VIDEOMODE_H
+
+#include <linux/types.h>
+#include <video/display_timing.h>
+
+/*
+ * Subsystem independent description of a videomode.
+ * Can be generated from struct display_timing.
+ */
+struct videomode {
+        unsigned long pixelclock;       /* pixelclock in Hz */
+
+        u32 hactive;
+        u32 hfront_porch;
+        u32 hback_porch;
+        u32 hsync_len;
+
+        u32 vactive;
+        u32 vfront_porch;
+        u32 vback_porch;
+        u32 vsync_len;
+
+        unsigned int dmt_flags; /* VESA DMT flags */
+        unsigned int data_flags; /* video data flags */
+};
+
+/**
+ * videomode_from_timing - convert display timing to videomode
+ * @disp: structure with all possible timing entries
+ * @vm: return value
+ * @index: index into the list of display timings in devicetree
+ *
+ * DESCRIPTION:
+ * This function converts a struct display_timing to a struct videomode.
+ */
+int videomode_from_timing(const struct display_timings *disp,
+                          struct videomode *vm, unsigned int index);
+
+#endif