[PATCH 1/2] of: add helper to parse display specs
Steffen Trumtrar
s.trumtrar at pengutronix.de
Mon Sep 24 08:35:23 PDT 2012
Parse a display-node with timings and hardware-specs from devictree.
Signed-off-by: Steffen Trumtrar <s.trumtrar at pengutronix.de>
---
Documentation/devicetree/bindings/video/display | 208 +++++++++++++++++++++++
drivers/of/Kconfig | 5 +
drivers/of/Makefile | 1 +
drivers/of/of_display.c | 157 +++++++++++++++++
include/linux/display.h | 85 +++++++++
include/linux/of_display.h | 15 ++
6 files changed, 471 insertions(+)
create mode 100644 Documentation/devicetree/bindings/video/display
create mode 100644 drivers/of/of_display.c
create mode 100644 include/linux/display.h
create mode 100644 include/linux/of_display.h
diff --git a/Documentation/devicetree/bindings/video/display b/Documentation/devicetree/bindings/video/display
new file mode 100644
index 0000000..722766a
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/display
@@ -0,0 +1,208 @@
+display bindings
+==================
+
+display-node
+------------
+
+required properties:
+ - none
+
+optional properties:
+ - default-timing: the default timing value
+ - width-mm, height-mm: Display dimensions in mm
+ - hsync-active-high (bool): Hsync pulse is active high
+ - vsync-active-high (bool): Vsync pulse is active high
+ - de-active-high (bool): Data-Enable pulse is active high
+ - pixelclk-inverted (bool): pixelclock is inverted
+ - pixel-per-clk
+ - link-width: number of channels (e.g. LVDS)
+ - bpp: bits-per-pixel
+
+timings-subnode
+---------------
+
+required properties:
+subnodes that specify
+ - hactive, vactive: Display resolution
+ - hfront-porch, hback-porch, hsync-len: Horizontal Display timing parameters
+ in pixels
+ vfront-porch, vback-porch, vsync-len: Vertical display timing parameters in
+ lines
+ - clock: displayclock in Hz
+
+There are different ways of describing a display and its capabilities. The devicetree
+representation corresponds to the one commonly found in datasheets for displays.
+The description of the display and its timing is split in two parts: first the display
+properties like size in mm and (optionally) multiple subnodes with the supported timings.
+If a display supports multiple signal timings, the default-timing can be specified.
+
+Example:
+
+ display at 0 {
+ width-mm = <800>;
+ height-mm = <480>;
+ default-timing = <&timing0>;
+ timings {
+ timing0: timing at 0 {
+ /* 1920x1080p24 */
+ clock = <52000000>;
+ hactive = <1920>;
+ vactive = <1080>;
+ hfront-porch = <25>;
+ hback-porch = <25>;
+ hsync-len = <25>;
+ vback-porch = <2>;
+ vfront-porch = <2>;
+ vsync-len = <2>;
+ hsync-active-high;
+ };
+ };
+ };
+
+Every property also supports the use of ranges, so the commonly used datasheet
+description with <min typ max>-tuples can be used.
+
+Example:
+
+ timing1: timing at 1 {
+ /* 1920x1080p24 */
+ clock = <148500000>;
+ hactive = <1920>;
+ vactive = <1080>;
+ hsync-len = <0 44 60>;
+ hfront-porch = <80 88 95>;
+ hback-porch = <100 148 160>;
+ vfront-porch = <0 4 6>;
+ vback-porch = <0 36 50>;
+ vsync-len = <0 5 6>;
+ };
+
+The "display"-property in a connector-node (e.g. hdmi, ldb,...) is used to connect
+the display to that driver.
+of_display expects a phandle, that specifies the display-node, in that property.
+
+Example:
+
+ hdmi at 00120000 {
+ status = "okay";
+ display = <&acme>;
+ };
+
+Usage in backend
+================
+
+A backend driver may choose to use the display directly and convert the timing
+ranges to a suitable mode. Or it may just use the conversion of the display timings
+to the required mode via the generic videomode struct.
+
+ dtb
+ |
+ | of_get_display
+ ↓
+ struct display
+ |
+ | videomode_from_timings
+ ↓
+ --- struct videomode ---
+ | |
+ videomode_to_displaymode | | videomode_to_fb_videomode
+ ↓ ↓
+ drm_display_mode fb_videomode
+
+
+Conversion to videomode
+=======================
+
+As device drivers normally work with some kind of video mode, the timings can be
+converted (may be just a simple copying of the typical value) to a generic videomode
+structure which then can be converted to the according mode used by the backend.
+
+Supported modes
+===============
+
+The generic videomode read in by the driver can be converted to the following
+modes with the following parameters
+
+struct fb_videomode
+===================
+
+ +----------+---------------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |upper_margin | | |
+ | | ↓ | | |
+ +----------###############################################----------+-------+
+ | # ↑ # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | left # | # right | hsync |
+ | margin # | xres # margin | len |
+ |<-------->#<---------------+--------------------------->#<-------->|<----->|
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # |yres # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # | # | |
+ | # ↓ # | |
+ +----------###############################################----------+-------+
+ | | ↑ | | |
+ | | |lower_margin | | |
+ | | ↓ | | |
+ +----------+---------------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |vsync_len | | |
+ | | ↓ | | |
+ +----------+---------------------------------------------+----------+-------+
+
+clock in nanoseconds
+
+struct drm_display_mode
+=======================
+
+ +----------+---------------------------------------------+----------+-------+
+ | | | | | ↑
+ | | | | | |
+ | | | | | |
+ +----------###############################################----------+-------+ |
+ | # ↑ ↑ ↑ # | | |
+ | # | | | # | | |
+ | # | | | # | | |
+ | # | | | # | | |
+ | # | | | # | | |
+ | # | | | hdisplay # | | |
+ | #<--+--------------------+-------------------># | | |
+ | # | | | # | | |
+ | # |vsync_start | # | | |
+ | # | | | # | | |
+ | # | |vsync_end | # | | |
+ | # | | |vdisplay # | | |
+ | # | | | # | | |
+ | # | | | # | | |
+ | # | | | # | | | vtotal
+ | # | | | # | | |
+ | # | | | hsync_start # | | |
+ | #<--+---------+----------+------------------------------>| | |
+ | # | | | # | | |
+ | # | | | hsync_end # | | |
+ | #<--+---------+----------+-------------------------------------->| |
+ | # | | ↓ # | | |
+ +----------####|#########|################################----------+-------+ |
+ | | | | | | | |
+ | | | | | | | |
+ | | ↓ | | | | |
+ +----------+-------------+-------------------------------+----------+-------+ |
+ | | | | | | |
+ | | | | | | |
+ | | ↓ | | | ↓
+ +----------+---------------------------------------------+----------+-------+
+ htotal
+ <------------------------------------------------------------------------->
+
+clock in kilohertz
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index dfba3e6..a4e3074 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -83,4 +83,9 @@ config OF_MTD
depends on MTD
def_bool y
+config OF_DISPLAY
+ def_bool y
+ help
+ helper to parse displays from the devicetree
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index e027f44..0756bee 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_OF_MDIO) += of_mdio.o
obj-$(CONFIG_OF_PCI) += of_pci.o
obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o
obj-$(CONFIG_OF_MTD) += of_mtd.o
+obj-$(CONFIG_OF_DISPLAY) += of_display.o
diff --git a/drivers/of/of_display.c b/drivers/of/of_display.c
new file mode 100644
index 0000000..632a351
--- /dev/null
+++ b/drivers/of/of_display.c
@@ -0,0 +1,157 @@
+/*
+ * OF helpers for parsing display timings
+ *
+ * Copyright (c) 2012 Steffen Trumtrar <s.trumtrar at pengutronix.de>, Pengutronix
+ *
+ * based on of_videomode.c by Sascha Hauer <s.hauer at pengutronix.de>
+ *
+ * This file is released under the GPLv2
+ */
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/display.h>
+#include <linux/of_display.h>
+#include <linux/fb.h>
+
+/* every signal_timing can be specified with either
+ * just the typical value or a range consisting of
+ * min/typ/max.
+ * This function helps handling this
+ */
+static int of_display_parse_property(struct device_node *np, char *name,
+ struct timing_entry *result)
+{
+ struct property *prop;
+ int length;
+ int cells;
+ int ret;
+
+ prop = of_find_property(np, name, &length);
+ if (!prop) {
+ pr_err("%s: could not find property %s\n", __func__,
+ name);
+ return -EINVAL;
+ }
+
+ cells = length / sizeof(u32);
+
+ if (cells == 1)
+ ret = of_property_read_u32_array(np, name, &result->typ, cells);
+ else if (cells == 3)
+ ret = of_property_read_u32_array(np, name, &result->min, cells);
+ else {
+ pr_err("%s: illegal timing specification in %s\n", __func__,
+ name);
+ return -EINVAL;
+ }
+
+ return ret;
+}
+
+struct display *of_get_display(struct device_node *np)
+{
+ struct device_node *display_np;
+ struct device_node *timing_np;
+ struct device_node *timings;
+ struct display *disp;
+ char *default_timing;
+
+ if (!np) {
+ pr_err("%s: no devicenode given\n", __func__);
+ return NULL;
+ }
+
+ display_np = of_parse_phandle(np, "display", 0);
+
+ if (!display_np) {
+ pr_err("%s: could not find display node\n", __func__);
+ return NULL;
+ }
+
+ disp = kmalloc(sizeof(struct display *), GFP_KERNEL);
+
+ memset(disp, 0, sizeof(struct display *));
+
+ of_property_read_u32(display_np, "width-mm", &disp->width_mm);
+ of_property_read_u32(display_np, "height-mm", &disp->height_mm);
+
+ timing_np = of_parse_phandle(display_np, "default-timing", 0);
+
+ if (!timing_np) {
+ pr_info("%s: no default-timing specified\n", __func__);
+ timing_np = of_find_node_by_name(np, "timing");
+ }
+
+ if (!timing_np) {
+ pr_info("%s: no timing specifications given\n", __func__);
+ return disp;
+ }
+
+ default_timing = (char *)timing_np->full_name;
+
+ timings = of_find_node_by_name(np, "timings");
+
+ disp->num_timings = 0;
+
+ disp->timings = kmalloc(sizeof(struct signal_timing *), GFP_KERNEL);
+
+ for_each_child_of_node(timings, timing_np) {
+ struct signal_timing *st;
+ int ret;
+
+ st = kmalloc(sizeof(struct signal_timing *), GFP_KERNEL);
+ disp->timings[disp->num_timings] = kmalloc(sizeof(struct signal_timing *), GFP_KERNEL);
+
+ ret |= of_display_parse_property(timing_np, "hback-porch", &st->hback_porch);
+ ret |= of_display_parse_property(timing_np, "hfront-porch", &st->hfront_porch);
+ ret |= of_display_parse_property(timing_np, "hactive", &st->hactive);
+ ret |= of_display_parse_property(timing_np, "hsync-len", &st->hsync_len);
+ ret |= of_display_parse_property(timing_np, "vback-porch", &st->vback_porch);
+ ret |= of_display_parse_property(timing_np, "vfront-porch", &st->vfront_porch);
+ ret |= of_display_parse_property(timing_np, "vactive", &st->vactive);
+ ret |= of_display_parse_property(timing_np, "vsync-len", &st->vsync_len);
+ ret |= of_display_parse_property(timing_np, "clock", &st->pixelclock);
+
+ if (strcmp(default_timing, timing_np->full_name) == 0)
+ disp->default_timing = disp->num_timings;
+
+ disp->timings[disp->num_timings] = st;
+ disp->num_timings++;
+ }
+
+ disp->vsync_pol_active_high = of_property_read_bool(display_np, "vsync-active-high");
+ disp->hsync_pol_active_high = of_property_read_bool(display_np, "hsync-active-high");
+ disp->de_pol_active_high = of_property_read_bool(display_np, "de-active-high");
+ disp->pixelclk_pol_inverted = of_property_read_bool(display_np, "pixelclk-inverted");
+ of_property_read_u32(display_np, "pixel-per-clk", &disp->if_pixel_per_clk);
+ of_property_read_u32(display_np, "link-width", &disp->if_link_width);
+ of_property_read_u32(display_np, "bpp", &disp->if_bpp);
+
+
+ pr_info("%s: got %d timings. Using #%d as default\n", __func__, disp->num_timings, disp->default_timing + 1);
+
+ return disp;
+}
+EXPORT_SYMBOL(of_get_display);
+
+int of_display_exists(struct device_node *np)
+{
+ struct device_node *display_np;
+ struct device_node *timing_np;
+
+ if (!np)
+ return -EINVAL;
+
+ display_np = of_parse_phandle(np, "display", 0);
+
+ if (!display_np)
+ return -EINVAL;
+
+ timing_np = of_parse_phandle(np, "default-timing", 0);
+
+ if (timing_np)
+ return 0;
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(of_display_exists);
diff --git a/include/linux/display.h b/include/linux/display.h
new file mode 100644
index 0000000..bb84ed9
--- /dev/null
+++ b/include/linux/display.h
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar at pengutronix.de>
+ *
+ * Hardware-description of a display
+ *
+ * This file is released under the GPLv2
+ */
+
+#ifndef __LINUX_DISPLAY_H
+#define __LINUX_DISPLAY_H
+
+#include <linux/list.h>
+
+#define OF_DEFAULT_TIMING -1
+
+struct display {
+ u32 width_mm;
+ u32 height_mm;
+ unsigned int num_timings;
+ unsigned int default_timing;
+
+ struct signal_timing **timings;
+
+ bool vsync_pol_active_high;
+ bool hsync_pol_active_high;
+ bool de_pol_active_high;
+ bool pixelclk_pol_inverted;
+
+ u32 if_bpp;
+ u32 if_link_width;
+ u32 if_pixel_per_clk;
+};
+
+struct timing_entry {
+ u32 min;
+ u32 typ;
+ u32 max;
+};
+
+struct signal_timing {
+ struct timing_entry pixelclock;
+
+ struct timing_entry hactive;
+ struct timing_entry hfront_porch;
+ struct timing_entry hback_porch;
+ struct timing_entry hsync_len;
+
+ struct timing_entry vactive;
+ struct timing_entry vfront_porch;
+ struct timing_entry vback_porch;
+ struct timing_entry vsync_len;
+};
+
+/* placeholder function until ranges are really needed */
+static inline u32 signal_timing_get_value(struct timing_entry *te, int index)
+{
+ return te->typ;
+}
+
+static inline void timings_release(struct display *disp)
+{
+ int i;
+ for (i = 0; i < disp->num_timings; i++)
+ kfree(disp->timings[i]);
+}
+
+static inline void display_release(struct display *disp)
+{
+ timings_release(disp);
+ kfree(disp->timings);
+}
+
+static inline struct signal_timing *display_get_timing(struct display *disp, int index)
+{
+ if (disp->num_timings >= index)
+ return disp->timings[index];
+ else
+ return NULL;
+}
+
+
+int of_display_exists(struct device_node *np);
+struct display *of_get_display(struct device_node *np);
+
+#endif /* __LINUX_DISPLAY_H */
diff --git a/include/linux/of_display.h b/include/linux/of_display.h
new file mode 100644
index 0000000..500ff94
--- /dev/null
+++ b/include/linux/of_display.h
@@ -0,0 +1,15 @@
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar at pengutronix.de>
+ *
+ * This file is released under the GPLv2
+ */
+
+#ifndef __LINUX_OF_DISPLAY_H
+#define __LINUX_OF_DISPALY_H
+
+#include <linux/fb.h>
+
+struct display *of_get_display(struct device_node *np);
+int of_display_exists(struct device_node *np);
+
+#endif
--
1.7.10.4
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