From 198fc108ee4c2cd3f08954eae6a819c81c03214b Mon Sep 17 00:00:00 2001 From: Eric Miao Date: Tue, 23 Dec 2008 17:49:43 +0800 Subject: [ARM] pxafb: add support for overlay1 and overlay2 as framebuffer devices PXA27x and later processors support overlay1 and overlay2 on-top of the base framebuffer (although under-neath the base is also possible). They support palette and no-palette RGB formats, as well as YUV formats (only available on overlay2). These overlays have dedicated DMA channels and behave in a similar way as a framebuffer. This heavily simplified and re-structured work is based on the original pxafb_overlay.c (which is pending for mainline merge for a long time). The major problems with this pxafb_overlay.c are (if you are interested in the history): 1. heavily redundant (the control logics for overlay1 and overlay2 are actually identical except for some small operations, which are now abstracted into a 'pxafb_layer_ops' structure) 2. a lot of useless and un-tested code (two workarounds which are now fixed on mature silicons) 3. cursorfb is actually useless, hardware cursor should not be used this way, and the code was actually un-tested for a long time. The code in this patch should be self-explanatory, I tried to add minimum comments. As said, this is basically simplified, there are several things still on the pending list: 1. palette mode is un-supported and un-tested (although re-using the palette code of the base framebuffer is actually very easy now with previous clean-up patches) 2. fb_pan_display for overlay(s) is un-supported 3. the base framebuffer can actually be abstracted by 'pxafb_layer' as well, which will help further re-use of the code and keep a better and consistent structure. (This is the reason I named it 'pxafb_layer' instead of 'pxafb_overlay' or something alike) See Documentation/fb/pxafb.txt for additional usage information. Signed-off-by: Eric Miao Cc: Rodolfo Giometti Signed-off-by: Eric Miao --- Documentation/fb/pxafb.txt | 84 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) (limited to 'Documentation') diff --git a/Documentation/fb/pxafb.txt b/Documentation/fb/pxafb.txt index ad94b5ca0095..d143a0a749f9 100644 --- a/Documentation/fb/pxafb.txt +++ b/Documentation/fb/pxafb.txt @@ -56,3 +56,87 @@ outputen:POLARITY pixclockpol:POLARITY pixel clock polarity 0 => falling edge, 1 => rising edge + + +Overlay Support for PXA27x and later LCD controllers +==================================================== + + PXA27x and later processors support overlay1 and overlay2 on-top of the + base framebuffer (although under-neath the base is also possible). They + support palette and no-palette RGB formats, as well as YUV formats (only + available on overlay2). These overlays have dedicated DMA channels and + behave in a similar way as a framebuffer. + + However, there are some differences between these overlay framebuffers + and normal framebuffers, as listed below: + + 1. overlay can start at a 32-bit word aligned position within the base + framebuffer, which means they have a start (x, y). This information + is encoded into var->nonstd (no, var->xoffset and var->yoffset are + not for such purpose). + + 2. overlay framebuffer is allocated dynamically according to specified + 'struct fb_var_screeninfo', the amount is decided by: + + var->xres_virtual * var->yres_virtual * bpp + + bpp = 16 -- for RGB565 or RGBT555 + = 24 -- for YUV444 packed + = 24 -- for YUV444 planar + = 16 -- for YUV422 planar (1 pixel = 1 Y + 1/2 Cb + 1/2 Cr) + = 12 -- for YUV420 planar (1 pixel = 1 Y + 1/4 Cb + 1/4 Cr) + + NOTE: + + a. overlay does not support panning in x-direction, thus + var->xres_virtual will always be equal to var->xres + + b. line length of overlay(s) must be on a 32-bit word boundary, + for YUV planar modes, it is a requirement for the component + with minimum bits per pixel, e.g. for YUV420, Cr component + for one pixel is actually 2-bits, it means the line length + should be a multiple of 16-pixels + + c. starting horizontal position (XPOS) should start on a 32-bit + word boundary, otherwise the fb_check_var() will just fail. + + d. the rectangle of the overlay should be within the base plane, + otherwise fail + + Applications should follow the sequence below to operate an overlay + framebuffer: + + a. open("/dev/fb[1-2]", ...) + b. ioctl(fd, FBIOGET_VSCREENINFO, ...) + c. modify 'var' with desired parameters: + 1) var->xres and var->yres + 2) larger var->yres_virtual if more memory is required, + usually for double-buffering + 3) var->nonstd for starting (x, y) and color format + 4) var->{red, green, blue, transp} if RGB mode is to be used + d. ioctl(fd, FBIOPUT_VSCREENINFO, ...) + e. ioctl(fd, FBIOGET_FSCREENINFO, ...) + f. mmap + g. ... + + 3. for YUV planar formats, these are actually not supported within the + framebuffer framework, application has to take care of the offsets + and lengths of each component within the framebuffer. + + 4. var->nonstd is used to pass starting (x, y) position and color format, + the detailed bit fields are shown below: + + 31 23 20 10 0 + +-----------------+---+----------+----------+ + | ... unused ... |FOR| XPOS | YPOS | + +-----------------+---+----------+----------+ + + FOR - color format, as defined by OVERLAY_FORMAT_* in pxafb.h + 0 - RGB + 1 - YUV444 PACKED + 2 - YUV444 PLANAR + 3 - YUV422 PLANAR + 4 - YUR420 PLANAR + + XPOS - starting horizontal position + YPOS - starting vertical position -- cgit v1.2.3-70-g09d2