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| author | Greg Kroah-Hartman <gregkh@suse.de> | 2011-12-12 15:19:40 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-12-12 15:19:53 -0800 |
| commit | 007d00d4c11b30b8fd7ff23b9d5aed3743e41f74 (patch) | |
| tree | d5c307ba2ee0e2f56fbc284db21b8bccf95d8a40 /arch/x86/include/asm/timer.h | |
| parent | c91043adaf50ef13609003120f3471783460fb71 (diff) | |
| parent | 68d3e668d245bb8300c7c6ddbc8508ddfe352e0f (diff) | |
| download | blackbird-op-linux-007d00d4c11b30b8fd7ff23b9d5aed3743e41f74.tar.gz blackbird-op-linux-007d00d4c11b30b8fd7ff23b9d5aed3743e41f74.zip | |
Merge branch 'for-next/dwc3' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb into usb-next
* 'for-next/dwc3' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb: (392 commits)
usb: dwc3: ep0: fix for possible early delayed_status
usb: dwc3: gadget: fix stream enable bit
usb: dwc3: ep0: fix GetStatus handling (again)
usb: dwc3: ep0: use dwc3_request for ep0 requsts instead of usb_request
usb: dwc3: use correct hwparam register for power mgm check
usb: dwc3: omap: move to module_platform_driver
usb: dwc3: workaround: missing disconnect event
usb: dwc3: workaround: missing USB3 Reset event
usb: dwc3: workaround: U1/U2 -> U0 transiton
usb: dwc3: gadget: return early in dwc3_cleanup_done_reqs()
usb: dwc3: ep0: handle delayed_status again
usb: dwc3: ep0: push ep0state into xfernotready processing
usb: dwc3: fix sparse errors
usb: dwc3: fix few coding style problems
usb: dwc3: move generic dwc3 code from gadget into core
usb: dwc3: use a helper function for operation mode setting
usb: dwc3: ep0: don't use ep0in for transfers
usb: dwc3: ep0: use proper endianess in SetFeature for wIndex
usb: dwc3: core: drop DWC3_EVENT_BUFFERS_MAX
usb: dwc3: omap: add multiple instances support to OMAP
...
Diffstat (limited to 'arch/x86/include/asm/timer.h')
| -rw-r--r-- | arch/x86/include/asm/timer.h | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h index fa7b9176b76c..431793e5d484 100644 --- a/arch/x86/include/asm/timer.h +++ b/arch/x86/include/asm/timer.h @@ -32,6 +32,22 @@ extern int no_timer_check; * (mathieu.desnoyers@polymtl.ca) * * -johnstul@us.ibm.com "math is hard, lets go shopping!" + * + * In: + * + * ns = cycles * cyc2ns_scale / SC + * + * Although we may still have enough bits to store the value of ns, + * in some cases, we may not have enough bits to store cycles * cyc2ns_scale, + * leading to an incorrect result. + * + * To avoid this, we can decompose 'cycles' into quotient and remainder + * of division by SC. Then, + * + * ns = (quot * SC + rem) * cyc2ns_scale / SC + * = quot * cyc2ns_scale + (rem * cyc2ns_scale) / SC + * + * - sqazi@google.com */ DECLARE_PER_CPU(unsigned long, cyc2ns); @@ -41,9 +57,14 @@ DECLARE_PER_CPU(unsigned long long, cyc2ns_offset); static inline unsigned long long __cycles_2_ns(unsigned long long cyc) { + unsigned long long quot; + unsigned long long rem; int cpu = smp_processor_id(); unsigned long long ns = per_cpu(cyc2ns_offset, cpu); - ns += cyc * per_cpu(cyc2ns, cpu) >> CYC2NS_SCALE_FACTOR; + quot = (cyc >> CYC2NS_SCALE_FACTOR); + rem = cyc & ((1ULL << CYC2NS_SCALE_FACTOR) - 1); + ns += quot * per_cpu(cyc2ns, cpu) + + ((rem * per_cpu(cyc2ns, cpu)) >> CYC2NS_SCALE_FACTOR); return ns; } |
