From patchwork Tue Feb 2 04:55:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Viresh Kumar X-Patchwork-Id: 374914 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING, SPF_HELO_NONE, SPF_PASS, TVD_PH_BODY_ACCOUNTS_PRE, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E6F6C433E0 for ; Tue, 2 Feb 2021 04:56:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC9FB60295 for ; Tue, 2 Feb 2021 04:56:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231856AbhBBE4B (ORCPT ); Mon, 1 Feb 2021 23:56:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231748AbhBBE4A (ORCPT ); Mon, 1 Feb 2021 23:56:00 -0500 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E05DAC0613ED for ; Mon, 1 Feb 2021 20:55:19 -0800 (PST) Received: by mail-pj1-x1030.google.com with SMTP id a20so1506340pjs.1 for ; Mon, 01 Feb 2021 20:55:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=KnjYJhpsvi+EI6uh+V9emtTk5rRYy/hy1WxcaaGRj88=; b=jMCQvOrib39iuufOoGnShhg7/M0QlLhgoR/DzvJuyYtnVlkdshCDsPRDtE/0jgK5k5 8aMyNcmbhs8BDR+1UNY05IUJIYrCvtXEVFL/6HNtEQlTwpxRbWt88F1EtwOZ9MxLQfyb DTNRKEzt4tnv9/2gVzxaMgFW+eo6yqLUy2gm6ZI8O7r1C+HdaJy0zFMT1s9WTtQtJYU2 1P3i1Ab8BqjM566cK4qfFZdO69Xb4RzEMAHOIGIz36rUvN0mBoX/UyA4W5qvitshuPCr BmfUrJDFbatH0Zfvc/D/1ftB2GWy9u/W70MmT6r5Owh7rLlxipN4VEyMXLt5CZbl8hj8 DQxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=KnjYJhpsvi+EI6uh+V9emtTk5rRYy/hy1WxcaaGRj88=; b=In0gfu5HnxVBR1voJjtN2PPllapBeiOmkcDNzaAyACTejaxvxqMPLGNZbi0wKjcHvs estdd1iQAQhdWxpVxy/xSYTugG1IeoSK7YipCKqsDnqhpXgyaLoRn8HjR/HA76l3SLUs tbaLvAG1hZX12G5DEtq2bxVi9Y4XUvKlpntgtVUuWh5rmcYmPbqcBrzSg6IgOB5Ho7Ny wb4Ou7WsQVe/rB6KN3SCXO5Hm76GyZXRcpSdCILZgHyr4vvgVX/9WE0x1F05Efho0xc7 aJNUUFAXQ4f/0GMPt0KKv6Xfe3kkOAqK6qr0icXh1XKPBhw0F+4eYl14XRNYVhdoLDEV BzuQ== X-Gm-Message-State: AOAM530h059tkihCWEWeaUroFXTVEgdAhutdZzW56uVpX8vN20OdZ+1F xK+ywFDszP+SZQuhFz13mPh9HA== X-Google-Smtp-Source: ABdhPJwS93fNsUH31dYgXN8xBzZ5bkht/DGUPiwXokd8KJoRuC/YLfOQ67hcBaOskP59AiVUpErNJg== X-Received: by 2002:a17:903:22c2:b029:de:45c0:69f2 with SMTP id y2-20020a17090322c2b02900de45c069f2mr20804008plg.26.1612241719095; Mon, 01 Feb 2021 20:55:19 -0800 (PST) Received: from localhost ([122.172.59.240]) by smtp.gmail.com with ESMTPSA id i3sm20044312pfq.194.2021.02.01.20.55.17 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Feb 2021 20:55:18 -0800 (PST) From: Viresh Kumar To: Rafael Wysocki , Viresh Kumar , Keguang Zhang , Kevin Hilman , Andy Gross , Bjorn Andersson , Krzysztof Kozlowski , Sudeep Holla , Thierry Reding , Jonathan Hunter , Matthias Brugger Cc: linux-pm@vger.kernel.org, Vincent Guittot , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-tegra@vger.kernel.org, linux-mediatek@lists.infradead.org Subject: [PATCH V2] cpufreq: Remove CPUFREQ_STICKY flag Date: Tue, 2 Feb 2021 10:25:11 +0530 Message-Id: X-Mailer: git-send-email 2.25.0.rc1.19.g042ed3e048af MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org During cpufreq driver's registration, if the ->init() callback for all the CPUs fail then there is not much point in keeping the driver around as it will only account for more of unnecessary noise, for example cpufreq core will try to suspend/resume the driver which never got registered properly. The removal of such a driver is avoided if the driver carries the CPUFREQ_STICKY flag. This was added way back [1] in 2004 and perhaps no one should ever need it now. A lot of drivers do set this flag, probably because they just copied it from other drivers. This was added earlier for some platforms [2] because their cpufreq drivers were getting registered before the CPUs were registered with subsys framework. And hence they used to fail. The same isn't true anymore though. The current code flow in the kernel is: start_kernel() -> kernel_init() -> kernel_init_freeable() -> do_basic_setup() -> driver_init() -> cpu_dev_init() -> subsys_system_register() //For CPUs -> do_initcalls() -> cpufreq_register_driver() Clearly, the CPUs will always get registered with subsys framework before any cpufreq driver can get probed. Remove the flag and update the relevant drivers. [1] https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/include/linux/cpufreq.h?id=7cc9f0d9a1ab04cedc60d64fd8dcf7df224a3b4d [2] https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/arm/mach-sa1100/cpu-sa1100.c?id=f59d3bbe35f6268d729f51be82af8325d62f20f5 Signed-off-by: Viresh Kumar --- V2: Detailed commit log. drivers/cpufreq/cpufreq-dt.c | 2 +- drivers/cpufreq/cpufreq.c | 3 +-- drivers/cpufreq/davinci-cpufreq.c | 2 +- drivers/cpufreq/loongson1-cpufreq.c | 2 +- drivers/cpufreq/mediatek-cpufreq.c | 2 +- drivers/cpufreq/omap-cpufreq.c | 2 +- drivers/cpufreq/qcom-cpufreq-hw.c | 2 +- drivers/cpufreq/s3c24xx-cpufreq.c | 2 +- drivers/cpufreq/s5pv210-cpufreq.c | 2 +- drivers/cpufreq/sa1100-cpufreq.c | 2 +- drivers/cpufreq/sa1110-cpufreq.c | 2 +- drivers/cpufreq/scmi-cpufreq.c | 2 +- drivers/cpufreq/scpi-cpufreq.c | 2 +- drivers/cpufreq/spear-cpufreq.c | 2 +- drivers/cpufreq/tegra186-cpufreq.c | 2 +- drivers/cpufreq/tegra194-cpufreq.c | 3 +-- drivers/cpufreq/vexpress-spc-cpufreq.c | 3 +-- include/linux/cpufreq.h | 17 +++++++---------- 18 files changed, 24 insertions(+), 30 deletions(-) diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c index ad4234518ef6..b1e1bdc63b01 100644 --- a/drivers/cpufreq/cpufreq-dt.c +++ b/drivers/cpufreq/cpufreq-dt.c @@ -175,7 +175,7 @@ static int cpufreq_exit(struct cpufreq_policy *policy) } static struct cpufreq_driver dt_cpufreq_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_IS_COOLING_DEV, .verify = cpufreq_generic_frequency_table_verify, .target_index = set_target, diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d0a3525ce27f..7d0ae968def7 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2810,8 +2810,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data) if (ret) goto err_boost_unreg; - if (!(cpufreq_driver->flags & CPUFREQ_STICKY) && - list_empty(&cpufreq_policy_list)) { + if (unlikely(list_empty(&cpufreq_policy_list))) { /* if all ->init() calls failed, unregister */ ret = -ENODEV; pr_debug("%s: No CPU initialized for driver %s\n", __func__, diff --git a/drivers/cpufreq/davinci-cpufreq.c b/drivers/cpufreq/davinci-cpufreq.c index 91f477a6cbc4..9e97f60f8199 100644 --- a/drivers/cpufreq/davinci-cpufreq.c +++ b/drivers/cpufreq/davinci-cpufreq.c @@ -95,7 +95,7 @@ static int davinci_cpu_init(struct cpufreq_policy *policy) } static struct cpufreq_driver davinci_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = davinci_target, .get = cpufreq_generic_get, diff --git a/drivers/cpufreq/loongson1-cpufreq.c b/drivers/cpufreq/loongson1-cpufreq.c index 86f612593e49..fb72d709db56 100644 --- a/drivers/cpufreq/loongson1-cpufreq.c +++ b/drivers/cpufreq/loongson1-cpufreq.c @@ -116,7 +116,7 @@ static int ls1x_cpufreq_exit(struct cpufreq_policy *policy) static struct cpufreq_driver ls1x_cpufreq_driver = { .name = "cpufreq-ls1x", - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = ls1x_cpufreq_target, .get = cpufreq_generic_get, diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c index 022e3e966e71..f2e491b25b07 100644 --- a/drivers/cpufreq/mediatek-cpufreq.c +++ b/drivers/cpufreq/mediatek-cpufreq.c @@ -463,7 +463,7 @@ static int mtk_cpufreq_exit(struct cpufreq_policy *policy) } static struct cpufreq_driver mtk_cpufreq_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_IS_COOLING_DEV, .verify = cpufreq_generic_frequency_table_verify, diff --git a/drivers/cpufreq/omap-cpufreq.c b/drivers/cpufreq/omap-cpufreq.c index 3694bb030df3..e035ee216b0f 100644 --- a/drivers/cpufreq/omap-cpufreq.c +++ b/drivers/cpufreq/omap-cpufreq.c @@ -144,7 +144,7 @@ static int omap_cpu_exit(struct cpufreq_policy *policy) } static struct cpufreq_driver omap_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = omap_target, .get = cpufreq_generic_get, diff --git a/drivers/cpufreq/qcom-cpufreq-hw.c b/drivers/cpufreq/qcom-cpufreq-hw.c index 9ed5341dc515..2a3b4f44488b 100644 --- a/drivers/cpufreq/qcom-cpufreq-hw.c +++ b/drivers/cpufreq/qcom-cpufreq-hw.c @@ -374,7 +374,7 @@ static struct freq_attr *qcom_cpufreq_hw_attr[] = { }; static struct cpufreq_driver cpufreq_qcom_hw_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_IS_COOLING_DEV, .verify = cpufreq_generic_frequency_table_verify, diff --git a/drivers/cpufreq/s3c24xx-cpufreq.c b/drivers/cpufreq/s3c24xx-cpufreq.c index 37efc0dc3f91..7380c32b238e 100644 --- a/drivers/cpufreq/s3c24xx-cpufreq.c +++ b/drivers/cpufreq/s3c24xx-cpufreq.c @@ -420,7 +420,7 @@ static int s3c_cpufreq_resume(struct cpufreq_policy *policy) #endif static struct cpufreq_driver s3c24xx_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .target = s3c_cpufreq_target, .get = cpufreq_generic_get, .init = s3c_cpufreq_init, diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c index bed496cf8d24..69786e5bbf05 100644 --- a/drivers/cpufreq/s5pv210-cpufreq.c +++ b/drivers/cpufreq/s5pv210-cpufreq.c @@ -574,7 +574,7 @@ static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this, } static struct cpufreq_driver s5pv210_driver = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = s5pv210_target, .get = cpufreq_generic_get, diff --git a/drivers/cpufreq/sa1100-cpufreq.c b/drivers/cpufreq/sa1100-cpufreq.c index 5c075ef6adc0..252b9fc26124 100644 --- a/drivers/cpufreq/sa1100-cpufreq.c +++ b/drivers/cpufreq/sa1100-cpufreq.c @@ -186,7 +186,7 @@ static int __init sa1100_cpu_init(struct cpufreq_policy *policy) } static struct cpufreq_driver sa1100_driver __refdata = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING, .verify = cpufreq_generic_frequency_table_verify, .target_index = sa1100_target, diff --git a/drivers/cpufreq/sa1110-cpufreq.c b/drivers/cpufreq/sa1110-cpufreq.c index d9d04d935b3a..1a83c8678a63 100644 --- a/drivers/cpufreq/sa1110-cpufreq.c +++ b/drivers/cpufreq/sa1110-cpufreq.c @@ -310,7 +310,7 @@ static int __init sa1110_cpu_init(struct cpufreq_policy *policy) /* sa1110_driver needs __refdata because it must remain after init registers * it with cpufreq_register_driver() */ static struct cpufreq_driver sa1110_driver __refdata = { - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING, .verify = cpufreq_generic_frequency_table_verify, .target_index = sa1110_target, diff --git a/drivers/cpufreq/scmi-cpufreq.c b/drivers/cpufreq/scmi-cpufreq.c index 491a0a24fb1e..5bd03b59887f 100644 --- a/drivers/cpufreq/scmi-cpufreq.c +++ b/drivers/cpufreq/scmi-cpufreq.c @@ -217,7 +217,7 @@ static int scmi_cpufreq_exit(struct cpufreq_policy *policy) static struct cpufreq_driver scmi_cpufreq_driver = { .name = "scmi", - .flags = CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY | + .flags = CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_IS_COOLING_DEV, .verify = cpufreq_generic_frequency_table_verify, diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c index e5140ad63db8..d6a698a1b5d1 100644 --- a/drivers/cpufreq/scpi-cpufreq.c +++ b/drivers/cpufreq/scpi-cpufreq.c @@ -191,7 +191,7 @@ static int scpi_cpufreq_exit(struct cpufreq_policy *policy) static struct cpufreq_driver scpi_cpufreq_driver = { .name = "scpi-cpufreq", - .flags = CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY | + .flags = CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_NEED_INITIAL_FREQ_CHECK | CPUFREQ_IS_COOLING_DEV, .verify = cpufreq_generic_frequency_table_verify, diff --git a/drivers/cpufreq/spear-cpufreq.c b/drivers/cpufreq/spear-cpufreq.c index 73bd8dc47074..7d0d62a06bf3 100644 --- a/drivers/cpufreq/spear-cpufreq.c +++ b/drivers/cpufreq/spear-cpufreq.c @@ -160,7 +160,7 @@ static int spear_cpufreq_init(struct cpufreq_policy *policy) static struct cpufreq_driver spear_cpufreq_driver = { .name = "cpufreq-spear", - .flags = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = spear_cpufreq_target, .get = cpufreq_generic_get, diff --git a/drivers/cpufreq/tegra186-cpufreq.c b/drivers/cpufreq/tegra186-cpufreq.c index e566ea298b59..5d1943e787b0 100644 --- a/drivers/cpufreq/tegra186-cpufreq.c +++ b/drivers/cpufreq/tegra186-cpufreq.c @@ -117,7 +117,7 @@ static unsigned int tegra186_cpufreq_get(unsigned int cpu) static struct cpufreq_driver tegra186_cpufreq_driver = { .name = "tegra186", - .flags = CPUFREQ_STICKY | CPUFREQ_HAVE_GOVERNOR_PER_POLICY | + .flags = CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, .get = tegra186_cpufreq_get, .verify = cpufreq_generic_frequency_table_verify, diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c index 6a67f36f3b80..a9620e4489ae 100644 --- a/drivers/cpufreq/tegra194-cpufreq.c +++ b/drivers/cpufreq/tegra194-cpufreq.c @@ -272,8 +272,7 @@ static int tegra194_cpufreq_set_target(struct cpufreq_policy *policy, static struct cpufreq_driver tegra194_cpufreq_driver = { .name = "tegra194", - .flags = CPUFREQ_STICKY | CPUFREQ_CONST_LOOPS | - CPUFREQ_NEED_INITIAL_FREQ_CHECK, + .flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = tegra194_cpufreq_set_target, .get = tegra194_get_speed, diff --git a/drivers/cpufreq/vexpress-spc-cpufreq.c b/drivers/cpufreq/vexpress-spc-cpufreq.c index f711d8eaea6a..51dfa9ae6cf5 100644 --- a/drivers/cpufreq/vexpress-spc-cpufreq.c +++ b/drivers/cpufreq/vexpress-spc-cpufreq.c @@ -486,8 +486,7 @@ static void ve_spc_cpufreq_ready(struct cpufreq_policy *policy) static struct cpufreq_driver ve_spc_cpufreq_driver = { .name = "vexpress-spc", - .flags = CPUFREQ_STICKY | - CPUFREQ_HAVE_GOVERNOR_PER_POLICY | + .flags = CPUFREQ_HAVE_GOVERNOR_PER_POLICY | CPUFREQ_NEED_INITIAL_FREQ_CHECK, .verify = cpufreq_generic_frequency_table_verify, .target_index = ve_spc_cpufreq_set_target, diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 9c8b7437b6cd..c8e40e91fe9b 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -387,8 +387,13 @@ struct cpufreq_driver { /* flags */ -/* driver isn't removed even if all ->init() calls failed */ -#define CPUFREQ_STICKY BIT(0) +/* + * Set by drivers that need to update internale upper and lower boundaries along + * with the target frequency and so the core and governors should also invoke + * the diver if the target frequency does not change, but the policy min or max + * may have changed. + */ +#define CPUFREQ_NEED_UPDATE_LIMITS BIT(0) /* loops_per_jiffy or other kernel "constants" aren't affected by frequency transitions */ #define CPUFREQ_CONST_LOOPS BIT(1) @@ -432,14 +437,6 @@ struct cpufreq_driver { */ #define CPUFREQ_IS_COOLING_DEV BIT(7) -/* - * Set by drivers that need to update internale upper and lower boundaries along - * with the target frequency and so the core and governors should also invoke - * the diver if the target frequency does not change, but the policy min or max - * may have changed. - */ -#define CPUFREQ_NEED_UPDATE_LIMITS BIT(8) - int cpufreq_register_driver(struct cpufreq_driver *driver_data); int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);