path: root/Documentation/arm
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authorTomi Valkeinen <tomi.valkeinen@ti.com>2012-11-09 15:52:20 +0200
committerTomi Valkeinen <tomi.valkeinen@ti.com>2012-11-13 09:52:24 +0200
commit0049fb2603b7afb1080776ee691dfa5a3d282357 (patch)
tree87a13be03223d34213fc9f213e0a480b365a4dd0 /Documentation/arm
parent3f5ba55e8f3698432c65b0ef77e83d22d5f64a79 (diff)
OMAPFB: use dma_alloc_attrs to allocate memory
Use dma_alloc_attrs to allocate memory instead of omap specific vram allocator. After this we can remove the omap vram allocator. There are some downsides to this change: 1) dma_alloc_attrs doesn't let us allocate at certain physical address. However, this should not be a problem as this feature of vram allocator is only used when reserving the framebuffer that was initialized by the bootloader, and we don't currently support "passing" a framebuffer from the bootloader to the kernel anyway. 2) dma_alloc_attrs, as of now, always ioremaps the allocated area, and we don't need the ioremap when using VRFB. This patch uses DMA_ATTR_NO_KERNEL_MAPPING for the allocation, but the flag is currently not operational. 3) OMAPFB_GET_VRAM_INFO ioctl cannot return real values anymore. I changed the ioctl to return 64M for all the values, which, I hope, the applications will interpret as "there's enough vram". 4) "vram" kernel parameter to define how much ram to reserve for video use no longer works. The user needs to enable CMA and use "cma" parameter. Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Diffstat (limited to 'Documentation/arm')
1 files changed, 4 insertions, 6 deletions
diff --git a/Documentation/arm/OMAP/DSS b/Documentation/arm/OMAP/DSS
index a564ceea9e9..4484e021290 100644
--- a/Documentation/arm/OMAP/DSS
+++ b/Documentation/arm/OMAP/DSS
@@ -285,7 +285,10 @@ FB0 +-- GFX ---- LCD ---- LCD
Misc notes
-OMAP FB allocates the framebuffer memory using the OMAP VRAM allocator.
+OMAP FB allocates the framebuffer memory using the standard dma allocator. You
+can enable Contiguous Memory Allocator (CONFIG_CMA) to improve the dma
+allocator, and if CMA is enabled, you use "cma=" kernel parameter to increase
+the global memory area for CMA.
Using DSI DPLL to generate pixel clock it is possible produce the pixel clock
of 86.5MHz (max possible), and with that you get 1280x1024@57 output from DVI.
@@ -301,11 +304,6 @@ framebuffer parameters.
Kernel boot arguments
- - Amount of total VRAM to preallocate and optionally a physical start
- memory address. For example, "10M". omapfb allocates memory for
- framebuffers from VRAM.
- Default video mode for specified displays. For example,
"dvi:800x400MR-24@60". See drivers/video/modedb.c.