1================================ 2Driver for EP93xx LCD controller 3================================ 4 5The EP93xx LCD controller can drive both standard desktop monitors and 6embedded LCD displays. If you have a standard desktop monitor then you 7can 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 video 15mode 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 the 25KHZ2PICOS macro to convert the pixel clock value. Most other values 26are in pixel clocks. See Documentation/fb/framebuffer.rst for further 27details. 28 29The ep93xxfb_mach_info structure for your board should look like the 30following:: 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 to 40your board initialisation function:: 41 42 ep93xx_register_fb(&some_board_fb_info); 43 44Video Attribute Flags 45===================== 46 47The ep93xxfb_mach_info structure has a flags field which can be used 48to configure the controller. The video attributes flags are fully 49documented in section 7 of the EP93xx users' guide. The following 50flags are available: 51 52=============================== ========================================== 53EP93XXFB_PCLK_FALLING Clock data on the falling edge of the 54 pixel clock. The default is to clock 55 data on the rising edge. 56 57EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By 58 default the blank signal is active low. 59 60EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By 61 default the horizontal sync is active low. 62 63EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By 64 default the vertical sync is active high. 65=============================== ========================================== 66 67The physical address of the framebuffer can be controlled using the 68following flags: 69 70=============================== ====================================== 71EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This 72 is the default setting. 73 74EP93XXFB_USE_SDCSN1 Use SDCSn[1] for the framebuffer. 75 76EP93XXFB_USE_SDCSN2 Use SDCSn[2] for the framebuffer. 77 78EP93XXFB_USE_SDCSN3 Use SDCSn[3] for the framebuffer. 79=============================== ====================================== 80 81Platform callbacks 82================== 83 84The EP93xx framebuffer driver supports three optional platform 85callbacks: setup, teardown and blank. The setup and teardown functions 86are called when the framebuffer driver is installed and removed 87respectively. The blank function is called whenever the display is 88blanked or unblanked. 89 90The setup and teardown devices pass the platform_device structure as 91an argument. The fb_info and ep93xxfb_mach_info structures can be 92obtained as follows:: 93 94 static int some_board_fb_setup(struct platform_device *pdev) 95 { 96 struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data; 97 struct fb_info *fb_info = platform_get_drvdata(pdev); 98 99 /* Board specific framebuffer setup */ 100 } 101 102Setting the video mode 103====================== 104 105The video mode is set using the following syntax:: 106 107 video=XRESxYRES[-BPP][@REFRESH] 108 109If the EP93xx video driver is built-in then the video mode is set on 110the Linux kernel command line, for example:: 111 112 video=ep93xx-fb:800x600-16@60 113 114If the EP93xx video driver is built as a module then the video mode is 115set when the module is installed:: 116 117 modprobe ep93xx-fb video=320x240 118 119Screenpage bug 120============== 121 122At least on the EP9315 there is a silicon bug which causes bit 27 of 123the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is 124an unofficial errata for this bug at:: 125 126 https://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2 127 128By default the EP93xx framebuffer driver checks if the allocated physical 129address has bit 27 set. If it does, then the memory is freed and an 130error is returned. The check can be disabled by adding the following 131option when loading the driver:: 132 133 ep93xx-fb.check_screenpage_bug=0 134 135In some cases it may be possible to reconfigure your SDRAM layout to 136avoid this bug. See section 13 of the EP93xx users' guide for details. 137