Hello again, first I want to thank You for Your fast answer. I work on MIPS 4Kec with linux kernel in version 2.6.15 from linux-mips (gcc 4.0.3 and gcc 3.4.3). >> There is no byte access to uncached mmaped memory. Is this correct statement? >Definately wrong. For example alot of mmapped I/O devices use uncached >byte accesses. Ok, in that case I have problem with byte access on mmaped uncached memory. Reason for previous post is next: If I write bytes to mmaped uncached memory like: ... ptr = (unsigned char*)mmap(0,lineSize,PROT_READ|PROT_WRITE,MAP_SHARED,fd0,0); ... for (i = 0; i < 12; i++) *ptr++ = 0xaa; this loop will not write all bytes correctly (every 4 bytes will have 0xaa as value), here is dump from Lauterbach debugger: ___address__|_0________4________8________C________0123456789ABCDEF D:83660000|>FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF ................ D:83660010| 000000AA 000000AA 000000AA 0000AA02 ................ and if I use bigger loop for (i = 0; i < 20; i++) *ptr++ = 0xaa; My linux will be crashed on 13 write. So, this is reason why I thought that byte access is not allowed on mmaped uncached memory. Is it possible that problem with byte access is related with device mmap function? >This stament if of course limited to the CPU's part of the system. Devices >may have their specific restrictions on access size and its not uncommon to >have such restrictions though that would seem unlikely for framebuffer >memory. Ok, I understood this. >If your particular CPU support it you may want to use cache mode "uncached >accellerated" for a framebuffer. It should deliver significtn performance >gains yet avoid the need for cache flushes. Thanks in advance Mile
