Am Mittwoch 18 August 2010 schrieb Thiago Macieira: > On Wednesday 18. August 2010 18.27.16 Ameya Palande wrote: > > Hi Thiago, > > > > On Wed, 2010-08-18 at 18:16 +0200, ext Thiago Macieira wrote: > > > On Wednesday 18 August 2010 15:09:37 Arjan van de Ven wrote: > > > > On 8/18/2010 3:19 AM, Carsten Munk wrote: > > > > > [this is not another SSSE3 discussion thread] > > > > > > > > > > Qt on OMAP3 has very big benefits from using NEON, just like using > > > > > SSSE3 does on Atom. However, we do not currently compile for NEON in > > > > > MeeGo for ARMv7 as not all ARMv7 has NEON (Marvell, Nvidia being > > > > > notable exceptions). > > > > > > > > > > We'd obviously like to use NEON on Nokia N900 but we're wondering how > > > > > to do this in the most ecosystem-friendly way. > > > > > > > > > > I have been talking to Thiago and he mentions that an environment > > > > > variable QT_NO_NEON=1 exists to disable NEON usage by Qt. > > > > > > > > > > So, my proposal is the following: > > > > > > > > > > Compile Qt with NEON support by default on ARMv7. Include script in > > > > > startup that provides QT_NO_NEON=1 to the UX session based on NEON > > > > > presence in /proc/cpuinfo. > > > > > > > > couldn't QT read /proc/cpuinfo (or do the equivalent of cpuid) instead > > > > of looking for the env variable? > > > > > > I don't know how the kernel detects the presence of the Neon coprocessor. > > > But looking at ARM documentation doesn't show any instruction for cpuid. > > > In general, for embedded devices, you don't need cpuid since "you know > > > what you put in your device". > > > > > > The kernel also passes the CPU capabilities to the process in the auxv, > > > but that is not exposed anywhere outside ld.so. > > > > How about "/proc/self/auxv"? > > Thanks, that's a good hint. That is binary format and thus easier to parse. > My > N900 shows 0x30d3 as features. If I read the kernel source right > (asm/hwcap.h), this translates to: > > swp half fastmult vfp edsp neon vfpv3
Once you do something like that, please let someone with a beagleboard xm test this to make sure that the neon detection also works on newer omap3's Till _______________________________________________ MeeGo-dev mailing list MeeGo-dev@meego.com http://lists.meego.com/listinfo/meego-dev
