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authorRyan Mallon <ryan@bluewatersys.com>2009-09-22 16:47:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-23 07:39:51 -0700
commit88017bda96a5fd568a982b01546c8fb1782dda62 (patch)
treefb31f14c593f882dac2db7acdfadbc469240dd6d /Documentation/fb/ep93xx-fb.txt
parentc6012189a40d33213ead5d15769fab615443206f (diff)
ep93xx video driver
EP93xx video driver plus documentation. Signed-off-by: Ryan Mallon <ryan@bluewatersys.com> Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: Daniele Venzano <linux@brownhat.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Krzysztof Helt <krzysztof.h1@poczta.fm> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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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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