On 24 May 2014, at 23:02, Andrew Turner <and...@fubar.geek.nz> wrote:
> On Sat, 24 May 2014 21:09:56 +0200 > Michael Tuexen <tue...@freebsd.org> wrote: > >> On 22 May 2014, at 09:09, Mark R V Murray <ma...@freebsd.org> wrote: >> >>> >>> On 21 May 2014, at 21:15, Hans Petter Selasky <h...@selasky.org> >>> wrote: >>> >>>> On 05/14/14 21:11, Mark Murray wrote: >>>>> Author: markm >>>>> Date: Wed May 14 19:11:15 2014 >>>>> New Revision: 266083 >>>>> URL: http://svnweb.freebsd.org/changeset/base/266083 >>>>> >>>>> Log: >>>>> Give suitably-endowed ARMs a register similar to the x86 TSC >>>>> register. >>>>> >>>> >>>> Hi, >>>> >>>> Regression issue: >>>> This commit prevents RPI-B from booting. >>> >>> Thanks, I’ll look at it ASAP. >> Doesn't the ARM1176 use for example >> MRC p15, 0, <Rd>, c15, c12, 1 ; Read Cycle Counter Register >> to read the value, whereas the >> you use >> __asm __volatile("mrc p15, 0, %0, c9, c13, 0": "=r" (ccnt)); > > On ARMv6 there is no guarantee of a cycle count register. On the > ARM1176 there is one in an implementation defined section of the system > control coprocessor. This is the c15 section above, and is accessible > as shown. > > On ARMv7 there are optional performance monitor extensions. These are > in parts of the c9 section of the coprocessor. As it is optional there > is no requirement for implementers to include this functionality, > however I would expect the ARM designs to include it, and most non-ARM > designs are likely aiming for performance so will also include them. > > If the ARMv7 processor has the performance extensions the existing code > appears correct to retrieve it. The code is #ifdef as #if defined(CPU_ARM1136) || defined(CPU_ARM1176) \ || defined(CPU_MV_PJ4B) \ || defined(CPU_CORTEXA) || defined(CPU_KRAIT) Isn't the Raspberry Pi defining CPU_ARM1176 and using ARMv6? So can we use the same code for all plattforms in the #ifdef? Best regards Michael > > Andrew > > _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
