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[88.21.103.182]) by smtp.gmail.com with ESMTPSA id o7sm1796086wmc.41.2019.12.02.22.09.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Dec 2019 22:09:48 -0800 (PST) Subject: Re: [PATCH v2 2/4] target/arm: Abstract the generic timer frequency To: Andrew Jeffery , qemu-arm@nongnu.org References: <20191203041440.6275-1-andrew@aj.id.au> <20191203041440.6275-3-andrew@aj.id.au> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <283c152b-b1c7-551e-bec0-c087b14de996@redhat.com> Date: Tue, 3 Dec 2019 07:09:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191203041440.6275-3-andrew@aj.id.au> Content-Language: en-US X-MC-Unique: PjQCemLiNvmMziaCOe-0Ew-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: joel@jms.id.au, peter.maydell@linaro.org, Richard Henderson , qemu-devel@nongnu.org, clg@kaod.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/3/19 5:14 AM, Andrew Jeffery wrote: > Prepare for SoCs such as the ASPEED AST2600 whose firmware configures > CNTFRQ to values significantly larger than the static 62.5MHz value > currently derived from GTIMER_SCALE. As the OS potentially derives its > timer periods from the CNTFRQ value the lack of support for running > QEMUTimers at the appropriate rate leads to sticky behaviour in the > guest. > > Substitute the GTIMER_SCALE constant with use of a helper to derive the > period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq > to the frequency associated with GTIMER_SCALE so current behaviour is > maintained. > > Signed-off-by: Andrew Jeffery > Reviewed-by: Richard Henderson > --- > target/arm/cpu.c | 2 ++ > target/arm/cpu.h | 10 ++++++++++ > target/arm/helper.c | 10 +++++++--- > 3 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 7a4ac9339bf9..5698a74061bb 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -974,6 +974,8 @@ static void arm_cpu_initfn(Object *obj) > if (tcg_enabled()) { > cpu->psci_version = 2; /* TCG implements PSCI 0.2 */ > } > + > + cpu->gt_cntfrq = NANOSECONDS_PER_SECOND / GTIMER_SCALE; > } > > static Property arm_cpu_reset_cbar_property = > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > index 83a809d4bac4..666c03871fdf 100644 > --- a/target/arm/cpu.h > +++ b/target/arm/cpu.h > @@ -932,8 +932,18 @@ struct ARMCPU { > */ > DECLARE_BITMAP(sve_vq_map, ARM_MAX_VQ); > DECLARE_BITMAP(sve_vq_init, ARM_MAX_VQ); > + > + /* Generic timer counter frequency, in Hz */ > + uint64_t gt_cntfrq; You can also explicit the unit by calling it 'gt_cntfrq_hz'. > }; > > +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > +{ > + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ Why inline this call? I doubt there is a significant performance gain. > + const unsigned int ns_per_s = 1000 * 1000 * 1000; > + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; > +} > + > void arm_cpu_post_init(Object *obj); > > uint64_t arm_cpu_mp_affinity(int idx, uint8_t clustersz); > diff --git a/target/arm/helper.c b/target/arm/helper.c > index 65c4441a3896..2622a9a8d02f 100644 > --- a/target/arm/helper.c > +++ b/target/arm/helper.c > @@ -2409,7 +2409,9 @@ static CPAccessResult gt_stimer_access(CPUARMState *env, > > static uint64_t gt_get_countervalue(CPUARMState *env) > { > - return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / GTIMER_SCALE; > + ARMCPU *cpu = env_archcpu(env); > + > + return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / gt_cntfrq_period_ns(cpu); > } > > static void gt_recalc_timer(ARMCPU *cpu, int timeridx) > @@ -2445,7 +2447,7 @@ static void gt_recalc_timer(ARMCPU *cpu, int timeridx) > * set the timer for as far in the future as possible. When the > * timer expires we will reset the timer for any remaining period. > */ > - if (nexttick > INT64_MAX / GTIMER_SCALE) { > + if (nexttick > INT64_MAX / gt_cntfrq_period_ns(cpu)) { > timer_mod_ns(cpu->gt_timer[timeridx], INT64_MAX); > } else { > timer_mod(cpu->gt_timer[timeridx], nexttick); > @@ -2874,11 +2876,13 @@ static const ARMCPRegInfo generic_timer_cp_reginfo[] = { > > static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) > { > + ARMCPU *cpu = env_archcpu(env); > + > /* Currently we have no support for QEMUTimer in linux-user so we > * can't call gt_get_countervalue(env), instead we directly > * call the lower level functions. > */ > - return cpu_get_clock() / GTIMER_SCALE; > + return cpu_get_clock() / gt_cntfrq_period_ns(cpu); > } > > static const ARMCPRegInfo generic_timer_cp_reginfo[] = { >