[PATCH v7 2/8] of: add helper to parse display timings

Steffen Trumtrar
2012-10-31T09:29:04Z

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
---
.../devicetree/bindings/video/display-timings.txt | 139 +++++++++++++++
drivers/of/Kconfig | 6 +
drivers/of/Makefile | 1 +
drivers/of/of_display_timings.c | 185 ++++++++++++++++++++
include/linux/of_display_timings.h | 20 +++
5 files changed, 351 insertions(+)
create mode 100644 Documentation/devicetree/bindings/video/display-timings.txt
create mode 100644 drivers/of/of_display_timings.c
create mode 100644 include/linux/of_display_timings.h

diff --git a/Documentation/devicetree/bindings/video/display-timings.txt b/Documentation/devicetree/bindings/video/display-timings.txt
new file mode 100644
index 0000000..04c94a3
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/display-timings.txt
@@ -0,0 +1,139 @@
+display-timings bindings
+==================
+
+display-timings-node
+------------
+
+required properties:
+ - none
+
+optional properties:
+ - native-mode: the native mode for the display, in case multiple modes are
+ provided. When omitted, assume the first node is the native.
+
+timings-subnode
+---------------
+
+required properties:
+ - 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-frequency: displayclock in Hz
+
+optional properties:
+ - hsync-active : Hsync pulse is active low/high/ignored
+ - vsync-active : Vsync pulse is active low/high/ignored
+ - de-active : Data-Enable pulse is active low/high/ignored
+ - pixelclk-inverted : pixelclock is inverted/non-inverted/ignored
+ - interlaced (bool)
+ - doublescan (bool)
+
+All the optional properties that are not bool follow the following logic:
+ <1> : high active
+ <0> : low active
+ omitted : not used on hardware
+
+There are different ways of describing the capabilities of a display. The devicetree
+representation corresponds to the one commonly found in datasheets for displays.
+If a display supports multiple signal timings, the native-mode can be specified.
+
+The parameters are defined as
+
+struct display_timing
+===================
+
+ +----------+---------------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |vback_porch | | |
+ | | ↓ | | |
+ +----------###############################################----------+-------+
+ | # ↑ # | |
+ | # | # | |
+ | hback # | # hfront | hsync |
+ | porch # | hactive # porch | len |
+ |<-------->#<---------------+--------------------------->#<-------->|<----->|
+ | # | # | |
+ | # |vactive # | |
+ | # | # | |
+ | # ↓ # | |
+ +----------###############################################----------+-------+
+ | | ↑ | | |
+ | | |vfront_porch | | |
+ | | ↓ | | |
+ +----------+---------------------------------------------+----------+-------+
+ | | ↑ | | |
+ | | |vsync_len | | |
+ | | ↓ | | |
+ +----------+---------------------------------------------+----------+-------+
+
+
+Example:
+
+ display-timings {
+ native-mode = <&timing0>;
+ timing0: 1920p24 {
+ /* 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 = <1>;
+ };
+ };
+
+Every required property also supports the use of ranges, so the commonly used
+datasheet description with <min typ max>-tuples can be used.
+
+Example:
+
+ timing1: timing {
+ /* 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>;
+ };
+
+
+Usage in backend
+================
+
+A backend driver may choose to use the display-timings 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_timing_list
+ ↓
+ struct display_timings
+ |
+ | videomode_from_timing
+ ↓
+ --- struct videomode ---
+ | |
+ videomode_to_displaymode | | videomode_to_fb_videomode
+ ↓ ↓
+ drm_display_mode fb_videomode
+
+The functions of_get_fb_videomode and of_get_display_mode are provided
+to conveniently get the respective mode representation from the devicetree.
+
+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.
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index dfba3e6..781e773 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -83,4 +83,10 @@ config OF_MTD
depends on MTD
def_bool y

+config OF_DISPLAY_TIMINGS
+ def_bool y
+ depends on DISPLAY_TIMING
+ help
+ helper to parse display timings from the devicetree
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index e027f44..c8e9603 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_TIMINGS) += of_display_timings.o
diff --git a/drivers/of/of_display_timings.c b/drivers/of/of_display_timings.c
new file mode 100644
index 0000000..388fe4c
--- /dev/null
+++ b/drivers/of/of_display_timings.c
@@ -0,0 +1,185 @@
+/*
+ * OF helpers for parsing display timings
+ *
+ * Copyright (c) 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>, Pengutronix
+ *
+ * based on of_videomode.c by Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This file is released under the GPLv2
+ */
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/of_display_timings.h>
+
+/**
+ * parse_property - parse timing_entry from device_node
+ * @np: device_node with the property
+ * @name: name of the property
+ * @result: will be set to the return value
+ *
+ * DESCRIPTION:
+ * Every display_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 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);
+ result->min = result->typ;
+ result->max = result->typ;
+ } 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;
+}
+
+/**
+ * of_get_display_timing - parse display_timing entry from device_node
+ * @np: device_node with the properties
+ **/
+struct display_timing *of_get_display_timing(struct device_node *np)
+{
+ struct display_timing *dt;
+ int ret = 0;
+
+ dt = kzalloc(sizeof(*dt), GFP_KERNEL);
+ if (!dt) {
+ pr_err("%s: could not allocate display_timing struct\n", __func__);
+ return NULL;
+ }
+
+ ret |= parse_property(np, "hback-porch", &dt->hback_porch);
+ ret |= parse_property(np, "hfront-porch", &dt->hfront_porch);
+ ret |= parse_property(np, "hactive", &dt->hactive);
+ ret |= parse_property(np, "hsync-len", &dt->hsync_len);
+ ret |= parse_property(np, "vback-porch", &dt->vback_porch);
+ ret |= parse_property(np, "vfront-porch", &dt->vfront_porch);
+ ret |= parse_property(np, "vactive", &dt->vactive);
+ ret |= parse_property(np, "vsync-len", &dt->vsync_len);
+ ret |= parse_property(np, "clock-frequency", &dt->pixelclock);
+
+ of_property_read_u32(np, "vsync-active", &dt->vsync_pol_active);
+ of_property_read_u32(np, "hsync-active", &dt->hsync_pol_active);
+ of_property_read_u32(np, "de-active", &dt->de_pol_active);
+ of_property_read_u32(np, "pixelclk-inverted", &dt->pixelclk_pol);
+ dt->interlaced = of_property_read_bool(np, "interlaced");
+ dt->doublescan = of_property_read_bool(np, "doublescan");
+
+ if (ret) {
+ pr_err("%s: error reading timing properties\n", __func__);
+ return NULL;
+ }
+
+ return dt;
+}
+EXPORT_SYMBOL_GPL(of_get_display_timing);
+
+/**
+ * of_get_display_timing_list - parse all display_timing entries from a device_node
+ * @np: device_node with the subnodes
+ **/
+struct display_timings *of_get_display_timing_list(struct device_node *np)
+{
+ struct device_node *timings_np;
+ struct device_node *entry;
+ struct device_node *native_mode;
+ struct display_timings *disp;
+
+ if (!np) {
+ pr_err("%s: no devicenode given\n", __func__);
+ return NULL;
+ }
+
+ timings_np = of_find_node_by_name(np, "display-timings");
+ if (!timings_np) {
+ pr_err("%s: could not find display-timings node\n", __func__);
+ return NULL;
+ }
+
+ disp = kzalloc(sizeof(*disp), GFP_KERNEL);
+
+ entry = of_parse_phandle(timings_np, "native-mode", 0);
+ /* assume first child as native mode if none provided */
+ if (!entry)
+ entry = of_get_next_child(np, NULL);
+ if (!entry) {
+ pr_err("%s: no timing specifications given\n", __func__);
+ return NULL;
+ }
+
+ pr_info("%s: using %s as default timing\n", __func__, entry->name);
+
+ native_mode = entry;
+
+ disp->num_timings = of_get_child_count(timings_np);
+ disp->timings = kzalloc(sizeof(struct display_timing *)*disp->num_timings,
+ GFP_KERNEL);
+ disp->num_timings = 0;
+ disp->native_mode = 0;
+
+ for_each_child_of_node(timings_np, entry) {
+ struct display_timing *dt;
+
+ dt = of_get_display_timing(entry);
+ if (!dt) {
+ /* to not encourage wrong devicetrees, fail in case of an error */
+ pr_err("%s: error in timing %d\n", __func__, disp->num_timings+1);
+ return NULL;
+ }
+
+ if (native_mode == entry)
+ disp->native_mode = disp->num_timings;
+
+ disp->timings[disp->num_timings] = dt;
+ disp->num_timings++;
+ }
+ of_node_put(timings_np);
+
+ if (disp->num_timings > 0)
+ pr_info("%s: got %d timings. Using timing #%d as default\n", __func__,
+ disp->num_timings , disp->native_mode + 1);
+ else {
+ pr_err("%s: no valid timings specified\n", __func__);
+ return NULL;
+ }
+ return disp;
+}
+EXPORT_SYMBOL_GPL(of_get_display_timing_list);
+
+/**
+ * of_display_timings_exists - check if a display-timings node is provided
+ * @np: device_node with the timing
+ **/
+int of_display_timings_exists(struct device_node *np)
+{
+ struct device_node *timings_np;
+ struct device_node *default_np;
+
+ if (!np)
+ return -EINVAL;
+
+ timings_np = of_parse_phandle(np, "display-timings", 0);
+ if (!timings_np)
+ return -EINVAL;
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(of_display_timings_exists);
diff --git a/include/linux/of_display_timings.h b/include/linux/of_display_timings.h
new file mode 100644
index 0000000..e4e1f22
--- /dev/null
+++ b/include/linux/of_display_timings.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ *
+ * display timings of helpers
+ *
+ * This file is released under the GPLv2
+ */
+
+#ifndef __LINUX_OF_DISPLAY_TIMINGS_H
+#define __LINUX_OF_DISPLAY_TIMINGS_H
+
+#include <linux/display_timing.h>
+
+#define OF_USE_NATIVE_MODE -1
+
+struct display_timings *of_get_display_timing_list(struct device_node *np);
+struct display_timing *of_get_display_timing(struct device_node *np);
+int of_display_timings_exists(struct device_node *np);
+
+#endif
--
1.7.10.4