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Fri, 10 Apr 2026 02:11:01 -0700 (PDT) Received: from [192.168.1.3] ([185.48.77.170]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488d58bf10fsm56934555e9.8.2026.04.10.02.11.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Apr 2026 02:11:01 -0700 (PDT) Message-ID: <140ce684-b172-4e1f-ae98-4edd88d4ca8b@linaro.org> Date: Fri, 10 Apr 2026 10:11:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 16/20] coresight: Add PM callbacks for sink device To: Leo Yan Cc: Suzuki K Poulose , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, Yeoreum Yun , Mark Rutland , Will Deacon , Yabin Cui , Keita Morisaki , Yuanfang Zhang , Greg Kroah-Hartman , Alexander Shishkin , Tamas Petz , Thomas Gleixner , Peter Zijlstra , Mike Leach References: <20260405-arm_coresight_path_power_management_improvement-v10-0-13e94754a8be@arm.com> <20260405-arm_coresight_path_power_management_improvement-v10-16-13e94754a8be@arm.com> <20260409144949.GT356832@e132581.arm.com> Content-Language: en-US From: James Clark In-Reply-To: <20260409144949.GT356832@e132581.arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260410_021103_779547_8406715E X-CRM114-Status: GOOD ( 24.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 09/04/2026 3:49 pm, Leo Yan wrote: > On Thu, Apr 09, 2026 at 03:30:56PM +0100, James Clark wrote: > > [...] > >>>>> @@ -1759,16 +1760,36 @@ static int coresight_pm_check(struct >>>>> coresight_path *path) >>>>>       if (source_has_cb) >>>>>           return 1; >>>>> +    sink_has_cb = coresight_ops(sink)->pm_save_disable && >>>>> +              coresight_ops(sink)->pm_restore_enable; >>>>> +    /* >>>>> +     * It is not permitted that the source has no callbacks >>>>> while the sink >>>>> +     * does, as the sink cannot be disabled without disabling >>>>> the source, >>>>> +     * which may lead to lockups. Alternatively, the ETM driver should >>>>> +     * enable self-hosted PM mode at probe (see etm4_probe()). >>>>> +     */ >>>>> +    if (sink_has_cb) { >>>>> +        pr_warn_once("coresight PM failed: source has no PM >>>>> callbacks; " >>>>> +                 "cannot safely control sink\n"); >>>> >>>> This prints out on my Orion board on a fresh boot because of how >>>> pm_save_enable is setup there. Do we really need the configuration >>>> of pm_save_enable for ETE/TRBE if we know that it always needs >>>> saving? > > Yeah, I can remove this check and always bind CPU PM ops for ETE. > >>>> It also stops warning if I rmmod and modprobe the module after >>>> booting. Seems like pm_save_enable is different depending on how the >>>> module is loaded which doesn't seem right. >>> >>> Thats because the warning is pr_warn_*once*() >> >> I don't think so, I tested it with a printf instead of a warn once and also >> tested modprobeing straight after a reboot. > > I am a bit surprised that Orion6 hits the CPU idle flow, as I observed > that idle states are not enabled on my board: > > # ls /sys/devices/system/cpu/cpu*/cpuidle > ls: cannot access '/sys/devices/system/cpu/cpu*/cpuidle': No such file or directory > /sys/devices/system/cpu/cpu0/cpuidle: total 0 drwxr-xr-x 9 root 0 Apr 10 10:08 .. drwxr-xr-x 2 root 0 Apr 10 10:10 state2 drwxr-xr-x 2 root 0 Apr 10 10:10 state1 drwxr-xr-x 2 root 0 Apr 10 10:10 state0 drwxr-xr-x 2 root 0 Apr 10 10:10 driver drwxr-xr-x 6 root 0 Apr 10 10:10 . > If you hit only once CPU idle notifier, it is good to add a > dump_stack() in coresight_cpu_pm_notify and print the "cmd" argument, > so we can know the calling coming from where. I am a bit suspect it > might be a glitch in CPUIdle layer. > > Thanks, > Leo cmd: 2 [ 7.878456] coresight_cpu_pm_notify+0x148/0x4b0 [ 7.878462] notifier_call_chain+0x8c/0x1e0 [ 7.878467] raw_notifier_call_chain+0x24/0x38 [ 7.878469] cpu_pm_exit+0x34/0x68 [ 7.878472] acpi_processor_ffh_lpi_enter+0x40/0x78 [ 7.878476] acpi_idle_lpi_enter+0x54/0x78 [ 7.878481] cpuidle_enter_state+0xb4/0x250 [ 7.878483] cpuidle_enter+0x44/0x68 [ 7.878487] do_idle+0x1e0/0x278 [ 7.878492] cpu_startup_entry+0x40/0x50 [ 7.878495] rest_init+0xec/0xf8 [ 7.878497] start_kernel+0x348/0x400 [ 7.878503] __primary_switched+0x88/0x98 -> zcat /proc/config.gz | grep IDLE CONFIG_CONTEXT_TRACKING_IDLE=y CONFIG_NO_HZ_IDLE=y CONFIG_CPU_IDLE=y CONFIG_CPU_IDLE_MULTIPLE_DRIVERS=y # CONFIG_CPU_IDLE_GOV_LADDER is not set CONFIG_CPU_IDLE_GOV_MENU=y # CONFIG_CPU_IDLE_GOV_TEO is not set CONFIG_DT_IDLE_STATES=y CONFIG_DT_IDLE_GENPD=y CONFIG_ARM_PSCI_CPUIDLE=y CONFIG_ARM_PSCI_CPUIDLE_DOMAIN=y CONFIG_ACPI_PROCESSOR_IDLE=y CONFIG_GENERIC_SMP_IDLE_THREAD=y CONFIG_GENERIC_IDLE_POLL_SETUP=y # CONFIG_IDLE_PAGE_TRACKING is not set # CONFIG_NETFILTER_XT_TARGET_IDLETIMER is not set