1280*800 resolution screen

Plat : AM3359

system:android 4.0.3

   I want to drive 1280*800 resolution screen,I modified the structure(TI-Android-ICS-4.0.3_AM335x_3.0.1/kernel/drivers/video/da8xx-fb.c) "static struct da8xx_panel known_lcd_panels[] " to

/* ThreeFive S9700RTWV35TR */

 [2] = {   .name = "TFC_S9700RTWV35TR_01B",

               .width = 1280,

                .height = 800,  

                  .hfp = 168,

                 .hbp = 0, 

                  .hsw = 0,

                  .vfp = 16,

                   .vbp = 0,  

                    .vsw = 0,

                    .pxl_clk = 68935680,   

                       .invert_pxl_clk = 0,  },

but   dma_alloc_coherent(NULL,          par->vram_size,          (resource_size_t *) &par->vram_phys,          GFP_KERNEL | GFP_DMA)  , apply memery is not successful!!!!!

Do I  need to modify other places?