From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:45548 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726025AbgFQI2f (ORCPT ); Wed, 17 Jun 2020 04:28:35 -0400 Date: Wed, 17 Jun 2020 10:27:03 +0200 From: Cornelia Huck Subject: Re: [kvm-unit-tests PATCH v9 06/12] s390x: clock and delays caluculations Message-ID: <20200617102704.7755e11a.cohuck@redhat.com> In-Reply-To: <1592213521-19390-7-git-send-email-pmorel@linux.ibm.com> References: <1592213521-19390-1-git-send-email-pmorel@linux.ibm.com> <1592213521-19390-7-git-send-email-pmorel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Pierre Morel Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@redhat.com, thuth@redhat.com 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. > - 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