From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001
From: root <root@artemis.panaceas.org>
Date: Fri, 25 Dec 2015 04:40:36 +0000
Subject: initial_commit

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 Documentation/fb/ep93xx-fb.txt | 135 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 Documentation/fb/ep93xx-fb.txt

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diff --git a/Documentation/fb/ep93xx-fb.txt b/Documentation/fb/ep93xx-fb.txt
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+================================
+Driver for EP93xx LCD controller
+================================
+
+The EP93xx LCD controller can drive both standard desktop monitors and
+embedded LCD displays. If you have a standard desktop monitor then you
+can use the standard Linux video mode database. In your board file:
+
+	static struct ep93xxfb_mach_info some_board_fb_info = {
+		.num_modes	= EP93XXFB_USE_MODEDB,
+		.bpp		= 16,
+	};
+
+If you have an embedded LCD display then you need to define a video
+mode for it as follows:
+
+	static struct fb_videomode some_board_video_modes[] = {
+		{
+			.name		= "some_lcd_name",
+			/* Pixel clock, porches, etc */
+		},
+	};
+
+Note that the pixel clock value is in pico-seconds. You can use the
+KHZ2PICOS macro to convert the pixel clock value. Most other values
+are in pixel clocks. See Documentation/fb/framebuffer.txt for further
+details.
+
+The ep93xxfb_mach_info structure for your board should look like the
+following:
+
+	static struct ep93xxfb_mach_info some_board_fb_info = {
+		.num_modes	= ARRAY_SIZE(some_board_video_modes),
+		.modes		= some_board_video_modes,
+		.default_mode	= &some_board_video_modes[0],
+		.bpp		= 16,
+	};
+
+The framebuffer device can be registered by adding the following to
+your board initialisation function:
+
+	ep93xx_register_fb(&some_board_fb_info);
+
+=====================
+Video Attribute Flags
+=====================
+
+The ep93xxfb_mach_info structure has a flags field which can be used
+to configure the controller. The video attributes flags are fully
+documented in section 7 of the EP93xx users' guide. The following
+flags are available:
+
+EP93XXFB_PCLK_FALLING		Clock data on the falling edge of the
+				pixel clock. The default is to clock
+				data on the rising edge.
+
+EP93XXFB_SYNC_BLANK_HIGH	Blank signal is active high. By
+				default the blank signal is active low.
+
+EP93XXFB_SYNC_HORIZ_HIGH	Horizontal sync is active high. By
+				default the horizontal sync is active low.
+
+EP93XXFB_SYNC_VERT_HIGH		Vertical sync is active high. By
+				default the vertical sync is active high.
+
+The physical address of the framebuffer can be controlled using the
+following flags:
+
+EP93XXFB_USE_SDCSN0		Use SDCSn[0] for the framebuffer. This
+				is the default setting.
+
+EP93XXFB_USE_SDCSN1		Use SDCSn[1] for the framebuffer.
+
+EP93XXFB_USE_SDCSN2		Use SDCSn[2] for the framebuffer.
+
+EP93XXFB_USE_SDCSN3		Use SDCSn[3] for the framebuffer.
+
+==================
+Platform callbacks
+==================
+
+The EP93xx framebuffer driver supports three optional platform
+callbacks: setup, teardown and blank. The setup and teardown functions
+are called when the framebuffer driver is installed and removed
+respectively. The blank function is called whenever the display is
+blanked or unblanked.
+
+The setup and teardown devices pass the platform_device structure as
+an argument. The fb_info and ep93xxfb_mach_info structures can be
+obtained as follows:
+
+	static int some_board_fb_setup(struct platform_device *pdev)
+	{
+		struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data;
+		struct fb_info *fb_info = platform_get_drvdata(pdev);
+
+		/* Board specific framebuffer setup */
+	}
+
+======================
+Setting the video mode
+======================
+
+The video mode is set using the following syntax:
+
+	video=XRESxYRES[-BPP][@REFRESH]
+
+If the EP93xx video driver is built-in then the video mode is set on
+the Linux kernel command line, for example:
+
+	video=ep93xx-fb:800x600-16@60
+
+If the EP93xx video driver is built as a module then the video mode is
+set when the module is installed:
+
+	modprobe ep93xx-fb video=320x240
+
+==============
+Screenpage bug
+==============
+
+At least on the EP9315 there is a silicon bug which causes bit 27 of
+the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is
+an unofficial errata for this bug at:
+	http://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2
+
+By default the EP93xx framebuffer driver checks if the allocated physical
+address has bit 27 set. If it does, then the memory is freed and an
+error is returned. The check can be disabled by adding the following
+option when loading the driver:
+
+      ep93xx-fb.check_screenpage_bug=0
+
+In some cases it may be possible to reconfigure your SDRAM layout to
+avoid this bug. See section 13 of the EP93xx users' guide for details.
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