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1================================2Driver for PXA25x LCD controller3================================4 5The driver supports the following options, either via6options=<OPTIONS> when modular or video=pxafb:<OPTIONS> when built in.7 8For example::9 10 modprobe pxafb options=vmem:2M,mode:640x480-8,passive11 12or on the kernel command line::13 14 video=pxafb:vmem:2M,mode:640x480-8,passive15 16vmem: VIDEO_MEM_SIZE17 18 Amount of video memory to allocate (can be suffixed with K or M19 for kilobytes or megabytes)20 21mode:XRESxYRES[-BPP]22 23 XRES == LCCR1_PPL + 124 25 YRES == LLCR2_LPP + 126 27 The resolution of the display in pixels28 29 BPP == The bit depth. Valid values are 1, 2, 4, 8 and 16.30 31pixclock:PIXCLOCK32 33 Pixel clock in picoseconds34 35left:LEFT == LCCR1_BLW + 136 37right:RIGHT == LCCR1_ELW + 138 39hsynclen:HSYNC == LCCR1_HSW + 140 41upper:UPPER == LCCR2_BFW42 43lower:LOWER == LCCR2_EFR44 45vsynclen:VSYNC == LCCR2_VSW + 146 47 Display margins and sync times48 49color | mono => LCCR0_CMS50 51 umm...52 53active | passive => LCCR0_PAS54 55 Active (TFT) or Passive (STN) display56 57single | dual => LCCR0_SDS58 59 Single or dual panel passive display60 614pix | 8pix => LCCR0_DPD62 63 4 or 8 pixel monochrome single panel data64 65hsync:HSYNC, vsync:VSYNC66 67 Horizontal and vertical sync. 0 => active low, 1 => active68 high.69 70dpc:DPC71 72 Double pixel clock. 1=>true, 0=>false73 74outputen:POLARITY75 76 Output Enable Polarity. 0 => active low, 1 => active high77 78pixclockpol:POLARITY79 80 pixel clock polarity81 0 => falling edge, 1 => rising edge82 83 84Overlay Support for PXA27x and later LCD controllers85====================================================86 87 PXA27x and later processors support overlay1 and overlay2 on-top of the88 base framebuffer (although under-neath the base is also possible). They89 support palette and no-palette RGB formats, as well as YUV formats (only90 available on overlay2). These overlays have dedicated DMA channels and91 behave in a similar way as a framebuffer.92 93 However, there are some differences between these overlay framebuffers94 and normal framebuffers, as listed below:95 96 1. overlay can start at a 32-bit word aligned position within the base97 framebuffer, which means they have a start (x, y). This information98 is encoded into var->nonstd (no, var->xoffset and var->yoffset are99 not for such purpose).100 101 2. overlay framebuffer is allocated dynamically according to specified102 'struct fb_var_screeninfo', the amount is decided by::103 104 var->xres_virtual * var->yres_virtual * bpp105 106 bpp = 16 -- for RGB565 or RGBT555107 108 bpp = 24 -- for YUV444 packed109 110 bpp = 24 -- for YUV444 planar111 112 bpp = 16 -- for YUV422 planar (1 pixel = 1 Y + 1/2 Cb + 1/2 Cr)113 114 bpp = 12 -- for YUV420 planar (1 pixel = 1 Y + 1/4 Cb + 1/4 Cr)115 116 NOTE:117 118 a. overlay does not support panning in x-direction, thus119 var->xres_virtual will always be equal to var->xres120 121 b. line length of overlay(s) must be on a 32-bit word boundary,122 for YUV planar modes, it is a requirement for the component123 with minimum bits per pixel, e.g. for YUV420, Cr component124 for one pixel is actually 2-bits, it means the line length125 should be a multiple of 16-pixels126 127 c. starting horizontal position (XPOS) should start on a 32-bit128 word boundary, otherwise the fb_check_var() will just fail.129 130 d. the rectangle of the overlay should be within the base plane,131 otherwise fail132 133 Applications should follow the sequence below to operate an overlay134 framebuffer:135 136 a. open("/dev/fb[1-2]", ...)137 b. ioctl(fd, FBIOGET_VSCREENINFO, ...)138 c. modify 'var' with desired parameters:139 140 1) var->xres and var->yres141 2) larger var->yres_virtual if more memory is required,142 usually for double-buffering143 3) var->nonstd for starting (x, y) and color format144 4) var->{red, green, blue, transp} if RGB mode is to be used145 146 d. ioctl(fd, FBIOPUT_VSCREENINFO, ...)147 e. ioctl(fd, FBIOGET_FSCREENINFO, ...)148 f. mmap149 g. ...150 151 3. for YUV planar formats, these are actually not supported within the152 framebuffer framework, application has to take care of the offsets153 and lengths of each component within the framebuffer.154 155 4. var->nonstd is used to pass starting (x, y) position and color format,156 the detailed bit fields are shown below::157 158 31 23 20 10 0159 +-----------------+---+----------+----------+160 | ... unused ... |FOR| XPOS | YPOS |161 +-----------------+---+----------+----------+162 163 FOR - color format, as defined by OVERLAY_FORMAT_* in pxafb.h164 165 - 0 - RGB166 - 1 - YUV444 PACKED167 - 2 - YUV444 PLANAR168 - 3 - YUV422 PLANAR169 - 4 - YUR420 PLANAR170 171 XPOS - starting horizontal position172 173 YPOS - starting vertical position174