Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 ================================ 2 Driver for EP93xx LCD controller 3 ================================ 4 5 The EP93xx LCD controller can drive both standard desktop monitors and 6 embedded LCD displays. If you have a standard desktop monitor then you 7 can 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 14 If you have an embedded LCD display then you need to define a video 15 mode 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 24 Note that the pixel clock value is in pico-seconds. You can use the 25 KHZ2PICOS macro to convert the pixel clock value. Most other values 26 are in pixel clocks. See Documentation/fb/framebuffer.txt for further 27 details. 28 29 The ep93xxfb_mach_info structure for your board should look like the 30 following: 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 39 The framebuffer device can be registered by adding the following to 40 your board initialisation function: 41 42 ep93xx_register_fb(&some_board_fb_info); 43 44 ===================== 45 Video Attribute Flags 46 ===================== 47 48 The ep93xxfb_mach_info structure has a flags field which can be used 49 to configure the controller. The video attributes flags are fully 50 documented in section 7 of the EP93xx users' guide. The following 51 flags are available: 52 53 EP93XXFB_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 57 EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By 58 default the blank signal is active low. 59 60 EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By 61 default the horizontal sync is active low. 62 63 EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By 64 default the vertical sync is active high. 65 66 The physical address of the framebuffer can be controlled using the 67 following flags: 68 69 EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This 70 is the default setting. 71 72 EP93XXFB_USE_SDCSN1 Use SDCSn[1] for the framebuffer. 73 74 EP93XXFB_USE_SDCSN2 Use SDCSn[2] for the framebuffer. 75 76 EP93XXFB_USE_SDCSN3 Use SDCSn[3] for the framebuffer. 77 78 ================== 79 Platform callbacks 80 ================== 81 82 The EP93xx framebuffer driver supports three optional platform 83 callbacks: setup, teardown and blank. The setup and teardown functions 84 are called when the framebuffer driver is installed and removed 85 respectively. The blank function is called whenever the display is 86 blanked or unblanked. 87 88 The setup and teardown devices pass the platform_device structure as 89 an argument. The fb_info and ep93xxfb_mach_info structures can be 90 obtained as follows: 91 92 static int some_board_fb_setup(struct platform_device *pdev) 93 { 94 struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data; 95 struct fb_info *fb_info = platform_get_drvdata(pdev); 96 97 /* Board specific framebuffer setup */ 98 } 99 100 ====================== 101 Setting the video mode 102 ====================== 103 104 The video mode is set using the following syntax: 105 106 video=XRESxYRES[-BPP][@REFRESH] 107 108 If the EP93xx video driver is built-in then the video mode is set on 109 the Linux kernel command line, for example: 110 111 video=ep93xx-fb:800x600-16@60 112 113 If the EP93xx video driver is built as a module then the video mode is 114 set when the module is installed: 115 116 modprobe ep93xx-fb video=320x240 117 118 ============== 119 Screenpage bug 120 ============== 121 122 At least on the EP9315 there is a silicon bug which causes bit 27 of 123 the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is 124 an unofficial errata for this bug at: 125 http://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2 126 127 By default the EP93xx framebuffer driver checks if the allocated physical 128 address has bit 27 set. If it does, then the memory is freed and an 129 error is returned. The check can be disabled by adding the following 130 option when loading the driver: 131 132 ep93xx-fb.check_screenpage_bug=0 133 134 In some cases it may be possible to reconfigure your SDRAM layout to 135 avoid this bug. See section 13 of the EP93xx users' guide for details.