On Wed, Aug 1, 2018 at 9:15 PM, Tomas Vanek via OpenOCD-devel <openocd-devel@lists.sourceforge.net> wrote: > On 01.08.2018 19:13, Christopher Head wrote: >> >> Hello! >> I was wondering about how OpenOCD was meant to interoperate with CPU >> caches. Right now, the Cortex M target has no cache management at all, which >> means that, on devices whose debug buses connect directly to RAM, any memory >> access through OpenOCD shows what’s in RAM, which may not be the same as >> what’s in d-cache. >> >> I had just always assumed that was intended behaviour until just now, when >> I saw a patch posted regarding cleaning caches on Cortex-A, presumably so >> that memory accesses would see what was most recently written by the CPU. >> >> What is OpenOCD’s policy regarding cache coherence around debug accesses >> to memory? If the policy is that they should be coherent, then I could >> probably provide a patch making this happen for Cortex M at some point. >> > > Hi Christopher, > > If you mean Cortex-M7 DCache, please try > > set CSW_HPROT3_CACHEABLE [expr 1 << 27] > samv.dap apcsw $CSW_HPROT3_CACHEABLE $CSW_HPROT3_CACHEABLE > > and MEM-AP access goes through DCache. > Of course, some fancy ui wold be nice. Might be set by default in target.cfg > or so. > > The only problem on Cortex-M7 is missing ICache flush after setting a RAM > breakpoint. > Not critical as you can use hw breakpoints only. > > Tom
Hi Tomas, have you already tested it? I'm checking ARM documents about Cortex-M7 but no mention about keeping cache coherency with the bus accessed through the debugger. Also Atmel/Microchip SAM-V documentation doesn't mention this important feature. I think such coherence mechanism should be too expensive for a MCU class of products and, often, it's not implemented even on more high-end MPU where the coherence mechanism is already in place for the SMP cores. Antonio ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ OpenOCD-devel mailing list OpenOCD-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/openocd-devel
