From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 954ABC43458 for ; Wed, 8 Jul 2026 08:28:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=m7OCS9ttjcsJjAtXg7NkqqhNNIFwWFmPdzpD3nDuHjg=; b=2TTFKskbpwKZItkt122FBS+nrT kxGs7MEgwRJcaypOw/ayGAVivXEEZkOlyKbbm6VUEYdt7BsLPxxsujOFk+v8jdfio2PTnwOp8IKWj wgUYsv+18IAgbXM5peM2KWsevRFkWAVqERJ3JUcJbzRGYxSYWZS5PGLbMNoAXK+KQpOQX4IEbZPFN LI6STR9o9fZg117c4S7iFSxOzLsndCNDDbheLkqu28D3P/+N+Usqf399RqWkOmbVQ7ls1NBJ9xQkJ 8Z6Et5KVCs1icrWs3uBIYmLW0aKCtEUtAVGdOKNtPYGTOH/U+sYyW0bPuRc7uJ1sAbP6vv4wejkQJ kpv8nRfA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whNdz-0000000GcP0-0APp; Wed, 08 Jul 2026 08:28:35 +0000 Received: from canpmsgout04.his.huawei.com ([113.46.200.219]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1whNdv-0000000GcNi-048J for linux-arm-kernel@lists.infradead.org; Wed, 08 Jul 2026 08:28:33 +0000 dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=m7OCS9ttjcsJjAtXg7NkqqhNNIFwWFmPdzpD3nDuHjg=; b=nJNt57MLrEVPte5Syar1+jRTg+YWjqen7Dz1aoXFz0/qSO1DjzXv/s+xQNLHSzE2c8xL6ZBJO a8y4KdgCkrkIT4/D1eHnyiTb+dVxJULuS1y8JNOd26kzKJaZ5ZCBJbWx/LBaSt617rIK3iiTjW3 CHxgZjTGpR1jcm5e7Z9DaDo= Received: from mail.maildlp.com (unknown [172.19.162.144]) by canpmsgout04.his.huawei.com (SkyGuard) with ESMTPS id 4gw9wm2VTLz1prPP; Wed, 8 Jul 2026 16:19:04 +0800 (CST) Received: from kwepemr200004.china.huawei.com (unknown [7.202.195.241]) by mail.maildlp.com (Postfix) with ESMTPS id 51A1A4056D; Wed, 8 Jul 2026 16:28:20 +0800 (CST) Received: from huawei.com (10.50.163.32) by kwepemr200004.china.huawei.com (7.202.195.241) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 8 Jul 2026 16:28:19 +0800 From: Pengjie Zhang To: , , , , , , , , , , , , , , , , , , , CC: , , , , , , Subject: [PATCH v2 1/2] ACPI: CPPC: add paired FFH feedback-counter read hook Date: Wed, 8 Jul 2026 16:28:17 +0800 Message-ID: <20260708082818.808041-2-zhangpengjie2@huawei.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20260708082818.808041-1-zhangpengjie2@huawei.com> References: <20260708082818.808041-1-zhangpengjie2@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.50.163.32] X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To kwepemr200004.china.huawei.com (7.202.195.241) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260708_012831_661819_7D757D5F X-CRM114-Status: GOOD ( 13.84 ) 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 cppc_get_perf_ctrs() reads the delivered and reference performance counters one at a time. Allow architectures to provide both FFH feedback counters in one operation when that either narrows the sampling window or avoids extra cross-CPU reads. Add a small FFH-specific hook for that case and fall back to the existing per-register reads when unsupported. Tested-by: Sumit Gupta Reviewed-by: Sumit Gupta Tested-by: Vanshidhar Konda Reviewed-by: Vanshidhar Konda Signed-off-by: Pengjie Zhang --- drivers/acpi/cppc_acpi.c | 50 ++++++++++++++++++++++++++++++++++++---- include/acpi/cppc_acpi.h | 7 ++++++ 2 files changed, 52 insertions(+), 5 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 9f572f481241..b6356476a46e 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1004,6 +1004,22 @@ int __weak cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val) return -ENOTSUPP; } +/** + * cpc_read_ffh_fb_ctrs() - Read FFH feedback counters together + * @cpunum: Target CPU + * @reg1: first CPPC register information + * @val1: place holder for first return value + * @reg2: second CPPC register information + * @val2: place holder for second return value + * + * Return: 0 on success, error code otherwise + */ +int __weak cpc_read_ffh_fb_ctrs(int cpunum, struct cpc_reg *reg1, + u64 *val1, struct cpc_reg *reg2, u64 *val2) +{ + return -EOPNOTSUPP; +} + /** * cpc_write_ffh() - Write FFH register * @cpunum: CPU number to write @@ -1496,6 +1512,33 @@ bool cppc_perf_ctrs_in_pcc_cpu(unsigned int cpu) } EXPORT_SYMBOL_GPL(cppc_perf_ctrs_in_pcc_cpu); +static int cppc_read_fb_ctrs(int cpunum, + struct cpc_register_resource *delivered_reg, + struct cpc_register_resource *reference_reg, + u64 *delivered, u64 *reference) +{ + int ret; + + /* + * For FFH feedback counters, try a paired read first to reduce + * sampling skew between delivered and reference counters. Fall + * back to the existing per-register reads if unsupported. + */ + if (CPC_IN_FFH(delivered_reg) && CPC_IN_FFH(reference_reg)) { + ret = cpc_read_ffh_fb_ctrs(cpunum, + &delivered_reg->cpc_entry.reg, delivered, + &reference_reg->cpc_entry.reg, reference); + if (ret != -EOPNOTSUPP) + return ret; + } + + ret = cpc_read(cpunum, delivered_reg, delivered); + if (ret) + return ret; + + return cpc_read(cpunum, reference_reg, reference); +} + /** * cppc_perf_ctrs_in_pcc - Check if any perf counters are in a PCC region. * @@ -1561,11 +1604,8 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) } } - ret = cpc_read(cpunum, delivered_reg, &delivered); - if (ret) - goto out_err; - - ret = cpc_read(cpunum, reference_reg, &reference); + ret = cppc_read_fb_ctrs(cpunum, delivered_reg, reference_reg, + &delivered, &reference); if (ret) goto out_err; diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h index 8693890a7275..5acebe62feac 100644 --- a/include/acpi/cppc_acpi.h +++ b/include/acpi/cppc_acpi.h @@ -176,6 +176,8 @@ extern int cppc_get_transition_latency(int cpu); extern bool cpc_ffh_supported(void); extern bool cpc_supported_by_cpu(void); extern int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val); +extern int cpc_read_ffh_fb_ctrs(int cpu, struct cpc_reg *reg1, u64 *val1, + struct cpc_reg *reg2, u64 *val2); extern int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val); extern int cppc_get_epp_perf(int cpunum, u64 *epp_perf); extern int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable); @@ -250,6 +252,11 @@ static inline int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val) { return -EOPNOTSUPP; } +static inline int cpc_read_ffh_fb_ctrs(int cpu, struct cpc_reg *reg1, u64 *val1, + struct cpc_reg *reg2, u64 *val2) +{ + return -EOPNOTSUPP; +} static inline int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val) { return -EOPNOTSUPP; -- 2.33.0