update timer frequencies
Hello, I am trying to implement a cpufreq driver for ARC CPUs. The point is that ARC timers (including those are used for timekeeping) are driven by the same clock as ARC CPU core(s). So if cpufreq driver changes CPU frequency timers frequency also updates. I added notification handler to ARC timer driver were I attempted to update clocksource frequency with "__clocksource_update_freq_hz()" but I found that actually the frequency didn't update. During my further investigation I mentioned that timekeeping framework doesn't allow frequency changes for more than 11%. This is quiet frustratingly: ARC cores supports such adjustments themselves but current framework API doesn't give us a chance to use this functionality and in fact it even forbids CPU frequency changes in runtime at all. Maybe I am mistaken and there is some way to get this going? Or maybe we can add some minor changes to timekeeping framework to resolve this issue (special flag that allows such changes or something like this?). Thanks. -- Best regards, Vlad Zakharov ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
Re: update timer frequencies
Vlad, On Fri, 10 Mar 2017, Vlad Zakharov wrote: > > I am trying to implement a cpufreq driver for ARC CPUs. The point is > that ARC timers (including those are used for timekeeping) are driven by > the same clock as ARC CPU core(s). To be honest: That's broken by design and you really should go and tell your hardware folks to fix that. Proper timekeeping is essential for any Operating System (not only Linux). It's well known for more than TWO decades that changing the frequency of the timekeeper clocksource is a complete disaster, but obviously every hardware vendor has to learn that the hard way instead of simply learning from history. > So if cpufreq driver changes CPU frequency timers frequency also > updates. I added notification handler to ARC timer driver were I > attempted to update clocksource frequency with > "__clocksource_update_freq_hz()" but I found that actually the frequency > didn't update. > > During my further investigation I mentioned that timekeeping framework > doesn't allow frequency changes for more than 11%. This is quiet > frustratingly: ARC cores supports such adjustments themselves but current > framework API doesn't give us a chance to use this functionality and in > fact it even forbids CPU frequency changes in runtime at all. It does not forbid CPU frequency changes. It forbids timekeeper clocksource frequency jumps. For a very good reason. Having frequency jumps disturbs timekeeping in several ways (monotonic behaviour, accuracy). > Maybe I am mistaken and there is some way to get this going? Or maybe we > can add some minor changes to timekeeping framework to resolve this issue > (special flag that allows such changes or something like this?). No, we won't add a special flag because the availability will just proliferate completely braindead hardware designs. We had a gazillion of horrible hacks which tried to make this work in the past, but none of them ever worked reliably under all circumstances. We won't bring them back. Your hardware design is broken by making the clocksource clock depend on the CPU frequency. Tell your hardware people to fix that or just use a seperate independent clocksource. Thanks, tglx ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
[PATCH 3.16 282/370] ARC: [arcompact] brown paper bag bug in unaligned access delay slot fixup
3.16.42-rc1 review patch. If anyone has any objections, please let me know.
--
From: Vineet Gupta
commit a524c218bc94c705886a0e0fedeee45d1931da32 upstream.
Reported-by: Jo-Philipp Wich
Fixes: 9aed02feae57bf7 ("ARC: [arcompact] handle unaligned access delay slot")
Cc: linux-ker...@vger.kernel.org
Cc: linux-snps-arc@lists.infradead.org
Signed-off-by: Vineet Gupta
Signed-off-by: Linus Torvalds
Signed-off-by: Ben Hutchings
---
arch/arc/kernel/unaligned.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arc/kernel/unaligned.c
+++ b/arch/arc/kernel/unaligned.c
@@ -242,7 +242,7 @@ int misaligned_fixup(unsigned long addre
/* clear any remanants of delay slot */
if (delay_mode(regs)) {
- regs->ret = regs->bta ~1U;
+ regs->ret = regs->bta & ~1U;
regs->status32 &= ~STATUS_DE_MASK;
} else {
regs->ret += state.instr_len;
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Re: [PATCH 03/20] asm-generic: Drop getrlimit and setrlimit syscalls from default list
On Thu, Mar 02, 2017 at 12:49:11AM +0530, Yury Norov wrote: > The newer prlimit64 syscall provides all the functionality provided by > the getrlimit and setrlimit syscalls and adds the pid of target process, > so future architectures won't need to include getrlimit and setrlimit. > > Therefore drop getrlimit and setrlimit syscalls from the generic syscall > list unless __ARCH_WANT_SET_GET_RLIMIT is defined by the architecture's > unistd.h prior to including asm-generic/unistd.h, and adjust all architectures > using the generic syscall list to define it so that no in-tree architectures > are affected. > > Cc: Arnd Bergmann > Cc: James Hogan > Cc: linux-a...@vger.kernel.org > Cc: linux-snps-arc@lists.infradead.org > Cc: Catalin Marinas > Cc: Will Deacon > Cc: linux-arm-ker...@lists.infradead.org > Cc: Mark Salter > Cc: Aurelien Jacquiot > Cc: linux-c6x-...@linux-c6x.org > Cc: Richard Kuo > Cc: linux-hexa...@vger.kernel.org > Cc: linux-me...@vger.kernel.org > Cc: Jonas Bonn > Cc: li...@lists.openrisc.net > Cc: Chen Liqin > Cc: Lennox Wu > Cc: Chris Metcalf > Cc: Guan Xuetao > Cc: Ley Foon Tan > Cc: nios2-...@lists.rocketboards.org > Cc: Yoshinori Sato > Cc: uclinux-h8-de...@lists.sourceforge.jp > Acked-by: Arnd Bergmann > Acked-by: Mark Salter [c6x] > Acked-by: James Hogan [metag] > Acked-by: Ley Foon Tan [nios2] > Acked-by: Stafford Horne [openrisc] > Acked-by: Vineet Gupta #arch/arc bits > Signed-off-by: Yury Norov > --- > arch/arc/include/uapi/asm/unistd.h | 1 + > arch/arm64/include/uapi/asm/unistd.h | 1 + > arch/c6x/include/uapi/asm/unistd.h | 1 + > arch/h8300/include/uapi/asm/unistd.h | 1 + > arch/hexagon/include/uapi/asm/unistd.h | 1 + > arch/metag/include/uapi/asm/unistd.h | 1 + > arch/nios2/include/uapi/asm/unistd.h | 1 + > arch/openrisc/include/uapi/asm/unistd.h | 1 + > arch/score/include/uapi/asm/unistd.h | 1 + > arch/tile/include/uapi/asm/unistd.h | 1 + > arch/unicore32/include/uapi/asm/unistd.h | 1 + > include/uapi/asm-generic/unistd.h| 5 + > 12 files changed, 16 insertions(+) For the arm64 part: Acked-by: Will Deacon Will ___ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc
