From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44886 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725554AbgFQLE7 (ORCPT ); Wed, 17 Jun 2020 07:04:59 -0400 Subject: Re: [kvm-unit-tests PATCH v9 06/12] s390x: clock and delays caluculations References: <1592213521-19390-1-git-send-email-pmorel@linux.ibm.com> <1592213521-19390-7-git-send-email-pmorel@linux.ibm.com> <20200617102704.7755e11a.cohuck@redhat.com> From: Pierre Morel Message-ID: <89cdae3e-1f50-03c1-e8ef-1f6b87a22fa9@linux.ibm.com> Date: Wed, 17 Jun 2020 13:04:52 +0200 MIME-Version: 1.0 In-Reply-To: <20200617102704.7755e11a.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Cornelia Huck Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@redhat.com, thuth@redhat.com On 2020-06-17 10:27, Cornelia Huck wrote: > On Mon, 15 Jun 2020 11:31:55 +0200 > Pierre Morel wrote: > >> The hardware gives us a good definition of the microsecond, >> let's keep this information and let the routine accessing >> the hardware keep all the information and return microseconds. >> >> Calculate delays in microseconds and take care about wrapping >> around zero. >> >> Define values with macros and use inlines to keep the >> milliseconds interface. >> >> Signed-off-by: Pierre Morel >> --- >> lib/s390x/asm/time.h | 29 +++++++++++++++++++++++++++-- >> 1 file changed, 27 insertions(+), 2 deletions(-) >> >> diff --git a/lib/s390x/asm/time.h b/lib/s390x/asm/time.h >> index 1791380..7f1d891 100644 >> --- a/lib/s390x/asm/time.h >> +++ b/lib/s390x/asm/time.h >> @@ -13,14 +13,39 @@ >> #ifndef ASM_S390X_TIME_H >> #define ASM_S390X_TIME_H >> >> -static inline uint64_t get_clock_ms(void) >> +#define STCK_SHIFT_US (63 - 51) >> +#define STCK_MAX ((1UL << 52) - 1) >> + >> +static inline uint64_t get_clock_us(void) >> { >> uint64_t clk; >> >> asm volatile(" stck %0 " : : "Q"(clk) : "memory"); >> >> /* Bit 51 is incrememented each microsecond */ > > That comment may now be a tad non-obvious, because the details are > hidden behind the #define? Anyway, no strong opinion. You are right. I find the macro's name is explicit so I remove the comment. > >> - return (clk >> (63 - 51)) / 1000; >> + return clk >> STCK_SHIFT_US; >> +} >> + >> +static inline void udelay(unsigned long us) >> +{ >> + unsigned long startclk = get_clock_us(); >> + unsigned long c; >> + >> + do { >> + c = get_clock_us(); >> + if (c < startclk) >> + c += STCK_MAX; >> + } while (c < startclk + us); >> +} >> + >> +static inline void mdelay(unsigned long ms) >> +{ >> + udelay(ms * 1000); >> +} >> + >> +static inline uint64_t get_clock_ms(void) >> +{ >> + return get_clock_us() / 1000; >> } >> >> #endif > > Acked-by: Cornelia Huck > Thanks, Pierre -- Pierre Morel IBM Lab Boeblingen