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 44===================== 45Video Attribute Flags 46===================== 47 48The ep93xxfb_mach_info structure has a flags field which can be used 49to configure the controller. The video attributes flags are fully 50documented in section 7 of the EP93xx users' guide. The following 51flags are available: 52 53=============================== ========================================== 54EP93XXFB_PCLK_FALLING Clock data on the falling edge of the 55 pixel clock. The default is to clock 56 data on the rising edge. 57 58EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By 59 default the blank signal is active low. 60 61EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By 62 default the horizontal sync is active low. 63 64EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By 65 default the vertical sync is active high. 66=============================== ========================================== 67 68The physical address of the framebuffer can be controlled using the 69following flags: 70 71=============================== ====================================== 72EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This 73 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 callbacks 84================== 85 86The EP93xx framebuffer driver supports three optional platform 87callbacks: setup, teardown and blank. The setup and teardown functions 88are called when the framebuffer driver is installed and removed 89respectively. The blank function is called whenever the display is 90blanked or unblanked. 91 92The setup and teardown devices pass the platform_device structure as 93an argument. The fb_info and ep93xxfb_mach_info structures can be 94obtained 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 mode 106====================== 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 on 113the Linux kernel command line, for example:: 114 115 video=ep93xx-fb:800x600-16@60 116 117If the EP93xx video driver is built as a module then the video mode is 118set when the module is installed:: 119 120 modprobe ep93xx-fb video=320x240 121 122============== 123Screenpage bug 124============== 125 126At least on the EP9315 there is a silicon bug which causes bit 27 of 127the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is 128an unofficial errata for this bug at:: 129 130 https://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2 131 132By default the EP93xx framebuffer driver checks if the allocated physical 133address has bit 27 set. If it does, then the memory is freed and an 134error is returned. The check can be disabled by adding the following 135option when loading the driver:: 136 137 ep93xx-fb.check_screenpage_bug=0 138 139In some cases it may be possible to reconfigure your SDRAM layout to 140avoid this bug. See section 13 of the EP93xx users' guide for details. 141