I have dumped TLB entries while mapping shared memory. On both cores M-Bit (MAS2[61]) is set in TLB0 entries. On both cores M-Bit is set for all valid TLB1 entries. TLB1 does contains some invalid entries which has M-Bit cleared. So I believe at this time the coherency is not the issue. Any further thoughts on the issue ?
I have modified dump_tlb_book3e function (found in arch/powerpc/xmon/xmon.c) function for BookE MMU to dump TLB entries. Regards, Farrukh Arshad -----Original Message----- From: tiejun.chen [mailto:tiejun.c...@windriver.com] Sent: Thursday, January 12, 2012 1:09 PM To: Arshad, Farrukh Cc: Scott Wood; linuxppc-dev@lists.ozlabs.org Subject: Re: Problem in getting shared memory access on P1022RDK Arshad, Farrukh wrote: > Adding more it, > > I have removed the shared memory kernel driver dependency just to narrow down > the problem area and I have written a small piece of code in user space. A > writer & a reader application which access the shared memory and I got the > same behavior as with the shared memory kernel driver. Interestingly, my user > space application work fine on P1022DS but not on P1022RDK however both using > the same CPU modules. > > When I write a simple string on shared memory from Core 1 it is read > at Core 0 properly When I write a simple string on shared memory from Core 0 > it is not read at Core 1. > Did you dump TLB entry to check page memory coherence attribute for a shared memory as I mentioned previously? This should be consistent on both sides. > With this test now I am sure the problem lies in the kernel itself. Any > pointers to look for the troubled area ? > > My application code is (error checking and other code is omitted) > > #define SHM_BASE 0x1C000000 > #define SHM_SIZE 0x400000 // 4 MB of Shared Memory > #define PAGE_SIZE (4*1024) > > fd = open(device, O_RDWR); You may need to add with 'O_SYNC'. Tiejun > > shm = malloc(SHM_SIZE + (PAGE_SIZE - 1)); if ( (unsigned long) shm % > PAGE_SIZE) { > shm += PAGE_SIZE - ((unsigned long)shm % PAGE_SIZE); } > > shm = mmap(shm, SHM_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED | > MAP_FIXED, fd, SHM_BASE); ...... > ...... write some string at shm. > > My memory partitioning for both systems is > > Core Base Address Size > Core 0 0x0000,0000 0x1000,0000 > Core 1 0x1000,0000 0x0C00,0000 > Shared Memory 0x1C00,0000 0x0400,0000 > > Regards, > Farrukh Arshad. > Mentor Graphics Pakistan _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
