On Wed, 16 Dec 2015 15:28:07 +0800 wrote: > On Wed, 16 Dec 2015 15:11:25 +0800 > Jisheng Zhang wrote: > > > Dear Daniel, > > > > On Tue, 15 Dec 2015 21:59:30 +0100 Daniel Lezcano wrote: > > > > > On 11/25/2015 04:42 PM, Jisheng Zhang wrote: > > > > Let's assume the counter value is 0xf000000, the pistachio clocksource > > oops, sorry, should be 0xf0000000. Do I need to send a v2 patch?
And in fact, clocksource_mmio_readw_down() also has similar issue, but it masks with c->mask before return, the c->mask is less than 32 bit (because the clocksource_mmio_init think number of valid bits > 32 or < 16 is invalid.) the higher 32 bits are masked off, so we never saw such issue. But we'd better to fix that, what's your opinion? Thank you very much, Jisheng > > > > > read cycles function would return 0xffffffff0fffffff, but it should > > > > return 0xfffffff. > > > > > > > > We fix this issue by calculating bitwise-not counter, then cast to > > > > cycle_t. > > > > > > > > Signed-off-by: Jisheng Zhang <[email protected]> > > > > > > Hi Jisheng, > > > > > > I tried to reproduce this behavior on x86_64 but without success. > > > > > > On which architecture did you produce this result ? Do you have a simple > > > test program to check with ? > > > > I have no HW platforms with pistachio, just read the code and run the > > following test code in x86_64 and x86_32: > > > > #include <stdio.h> > > unsigned long long pistachio_clocksource_read_cycles() > > { > > unsigned int counter = 0xf000000; > > should be unsigned int counter = 0xf0000000; > > > return ~(unsigned long long)counter; > > } > > int main() > > { > > printf("%llx\n", pistachio_clocksource_read_cycles()); > > return 0; > > } > > > > Thanks, > > Jisheng > > > > _______________________________________________ > > linux-arm-kernel mailing list > > [email protected] > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
