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1================================2Driver for EP93xx LCD controller3================================4 5The EP93xx LCD controller can drive both standard desktop monitors and6embedded LCD displays. If you have a standard desktop monitor then you7can use the standard Linux video mode database. In your board file::8 9 static struct ep93xxfb_mach_info some_board_fb_info = {10 .num_modes = EP93XXFB_USE_MODEDB,11 .bpp = 16,12 };13 14If you have an embedded LCD display then you need to define a video15mode for it as follows::16 17 static struct fb_videomode some_board_video_modes[] = {18 {19 .name = "some_lcd_name",20 /* Pixel clock, porches, etc */21 },22 };23 24Note that the pixel clock value is in pico-seconds. You can use the25KHZ2PICOS macro to convert the pixel clock value. Most other values26are in pixel clocks. See Documentation/fb/framebuffer.rst for further27details.28 29The ep93xxfb_mach_info structure for your board should look like the30following::31 32 static struct ep93xxfb_mach_info some_board_fb_info = {33 .num_modes = ARRAY_SIZE(some_board_video_modes),34 .modes = some_board_video_modes,35 .default_mode = &some_board_video_modes[0],36 .bpp = 16,37 };38 39The framebuffer device can be registered by adding the following to40your board initialisation function::41 42 ep93xx_register_fb(&some_board_fb_info);43 44=====================45Video Attribute Flags46=====================47 48The ep93xxfb_mach_info structure has a flags field which can be used49to configure the controller. The video attributes flags are fully50documented in section 7 of the EP93xx users' guide. The following51flags are available:52 53=============================== ==========================================54EP93XXFB_PCLK_FALLING Clock data on the falling edge of the55 pixel clock. The default is to clock56 data on the rising edge.57 58EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By59 default the blank signal is active low.60 61EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By62 default the horizontal sync is active low.63 64EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By65 default the vertical sync is active high.66=============================== ==========================================67 68The physical address of the framebuffer can be controlled using the69following flags:70 71=============================== ======================================72EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This73 is the default setting.74 75EP93XXFB_USE_SDCSN1 Use SDCSn[1] for the framebuffer.76 77EP93XXFB_USE_SDCSN2 Use SDCSn[2] for the framebuffer.78 79EP93XXFB_USE_SDCSN3 Use SDCSn[3] for the framebuffer.80=============================== ======================================81 82==================83Platform callbacks84==================85 86The EP93xx framebuffer driver supports three optional platform87callbacks: setup, teardown and blank. The setup and teardown functions88are called when the framebuffer driver is installed and removed89respectively. The blank function is called whenever the display is90blanked or unblanked.91 92The setup and teardown devices pass the platform_device structure as93an argument. The fb_info and ep93xxfb_mach_info structures can be94obtained as follows::95 96 static int some_board_fb_setup(struct platform_device *pdev)97 {98 struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data;99 struct fb_info *fb_info = platform_get_drvdata(pdev);100 101 /* Board specific framebuffer setup */102 }103 104======================105Setting the video mode106======================107 108The video mode is set using the following syntax::109 110 video=XRESxYRES[-BPP][@REFRESH]111 112If the EP93xx video driver is built-in then the video mode is set on113the Linux kernel command line, for example::114 115 video=ep93xx-fb:800x600-16@60116 117If the EP93xx video driver is built as a module then the video mode is118set when the module is installed::119 120 modprobe ep93xx-fb video=320x240121 122==============123Screenpage bug124==============125 126At least on the EP9315 there is a silicon bug which causes bit 27 of127the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is128an unofficial errata for this bug at::129 130 https://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2131 132By default the EP93xx framebuffer driver checks if the allocated physical133address has bit 27 set. If it does, then the memory is freed and an134error is returned. The check can be disabled by adding the following135option when loading the driver::136 137 ep93xx-fb.check_screenpage_bug=0138 139In some cases it may be possible to reconfigure your SDRAM layout to140avoid this bug. See section 13 of the EP93xx users' guide for details.141