From patchwork Mon Nov 29 19:11:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cristian Marussi X-Patchwork-Id: 12693977 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 AD7E1C433EF for ; Mon, 29 Nov 2021 19:18:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id: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=Ub0UWQkDgt4IYGy84CRjRJY5LDa+Qp5S8k4YhW4jncY=; b=yUCrMcbvEohm7F 6QsB/Z2q3/aHlzvMerf4ILahgzVfUI/jOOpoIYK49SfjFXu2fat/AuEkrJHhlopdqMOmfo1NZLYCQ kgSnB5Km1KrDeA5IiXj7UgyGkhRcW7bNqHS/haOSF3KYNNWTicO11Tc9eZdexf0GDW61JpRqx83AT R8lJzTwEef+mNUrbFKvHw51PTdhH78pfEJoMU7UpI7sFry8NvkPZd6eZuSei61nkDK+Q9etluJZii lTSZ93lU//SjsZc8ULQHnewxdBH3WsTuc2B1D9dQkLga71GoA52/80XfzvMDsJ5VqI0Ys8cerf317 cNtPsu1hOhx9ORXXMaAw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrm9Q-0022x3-Sb; Mon, 29 Nov 2021 19:17:21 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mrm56-0020m9-Oa for linux-arm-kernel@lists.infradead.org; Mon, 29 Nov 2021 19:12:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6BF3E150C; Mon, 29 Nov 2021 11:12:52 -0800 (PST) Received: from e120937-lin.home (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0D6DA3F5A1; Mon, 29 Nov 2021 11:12:50 -0800 (PST) From: Cristian Marussi To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: sudeep.holla@arm.com, james.quinlan@broadcom.com, Jonathan.Cameron@Huawei.com, f.fainelli@gmail.com, etienne.carriere@linaro.org, vincent.guittot@linaro.org, souvik.chakravarty@arm.com, cristian.marussi@arm.com Subject: [PATCH v7 12/16] firmware: arm_scmi: Add atomic mode support to smc transport Date: Mon, 29 Nov 2021 19:11:52 +0000 Message-Id: <20211129191156.29322-13-cristian.marussi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211129191156.29322-1-cristian.marussi@arm.com> References: <20211129191156.29322-1-cristian.marussi@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211129_111252_939632_7532ADE2 X-CRM114-Status: GOOD ( 17.86 ) 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: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add a Kernel configuration option to enable SCMI SMC transport atomic mode operation for selected SCMI transactions and leave it as default disabled. Substitute mutex usages with busy-waiting and declare smc transport as .atomic_enabled if such Kernel configuration option is enabled. Signed-off-by: Cristian Marussi --- v5 --> v6 - remove usage of atomic_capable - removed needless union - reviewed Kconfig help v4 --> v5 - removed RFC tag - add CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE option - add .atomic_enable support - make atomic_capable dependent on CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE - make also usage of mutexes vs busy-waiting dependent on CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE --- drivers/firmware/arm_scmi/Kconfig | 14 +++++++ drivers/firmware/arm_scmi/smc.c | 66 ++++++++++++++++++++++++++++--- 2 files changed, 74 insertions(+), 6 deletions(-) diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig index 638ecec89ff1..d429326433d1 100644 --- a/drivers/firmware/arm_scmi/Kconfig +++ b/drivers/firmware/arm_scmi/Kconfig @@ -78,6 +78,20 @@ config ARM_SCMI_TRANSPORT_SMC If you want the ARM SCMI PROTOCOL stack to include support for a transport based on SMC, answer Y. +config ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + bool "Enable atomic mode support for SCMI SMC transport" + depends on ARM_SCMI_TRANSPORT_SMC + help + Enable support of atomic operation for SCMI SMC based transport. + + If you want the SCMI SMC based transport to operate in atomic + mode, avoiding any kind of sleeping behaviour for selected + transactions on the TX path, answer Y. + Enabling atomic mode operations allows any SCMI driver using this + transport to optionally ask for atomic SCMI transactions and operate + in atomic context too, at the price of using a number of busy-waiting + primitives all over instead. If unsure say N. + config ARM_SCMI_TRANSPORT_VIRTIO bool "SCMI transport based on VirtIO" depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c index b2f31d3feb10..0fc49cb49185 100644 --- a/drivers/firmware/arm_scmi/smc.c +++ b/drivers/firmware/arm_scmi/smc.c @@ -7,6 +7,7 @@ */ #include +#include #include #include #include @@ -14,6 +15,9 @@ #include #include #include +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE +#include +#endif #include #include "common.h" @@ -23,14 +27,23 @@ * * @cinfo: SCMI channel info * @shmem: Transmit/Receive shared memory area - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area + * @shmem_lock: Lock to protect access to Tx/Rx shared memory area. + * Used when NOT operating in atomic mode. + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area. + * Used when operating in atomic mode. * @func_id: smc/hvc call function id */ struct scmi_smc { struct scmi_chan_info *cinfo; struct scmi_shared_mem __iomem *shmem; +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + /* Protect access to shmem area */ struct mutex shmem_lock; +#else +#define INFLIGHT_NONE MSG_TOKEN_MAX + atomic_t inflight; +#endif u32 func_id; }; @@ -54,6 +67,46 @@ static bool smc_chan_available(struct device *dev, int idx) return true; } +static inline void smc_channel_lock_init(struct scmi_smc *scmi_info) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_init(&scmi_info->shmem_lock); +#else + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); +#endif +} + +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE +static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight) +{ + int ret; + + ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq); + + return ret == INFLIGHT_NONE; +} +#endif + +static inline void +smc_channel_lock_acquire(struct scmi_smc *scmi_info, + struct scmi_xfer *xfer __maybe_unused) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_lock(&scmi_info->shmem_lock); +#else + spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight)); +#endif +} + +static inline void smc_channel_lock_release(struct scmi_smc *scmi_info) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_unlock(&scmi_info->shmem_lock); +#else + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); +#endif +} + static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, bool tx) { @@ -114,7 +167,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, scmi_info->func_id = func_id; scmi_info->cinfo = cinfo; - mutex_init(&scmi_info->shmem_lock); + smc_channel_lock_init(scmi_info); cinfo->transport_info = scmi_info; return 0; @@ -140,10 +193,10 @@ static int smc_send_message(struct scmi_chan_info *cinfo, struct arm_smccc_res res; /* - * Channel lock will be released only once response has been + * Channel will be released only once response has been * surely fully retrieved, so after .mark_txdone() */ - mutex_lock(&scmi_info->shmem_lock); + smc_channel_lock_acquire(scmi_info, xfer); shmem_tx_prepare(scmi_info->shmem, xfer); @@ -151,7 +204,7 @@ static int smc_send_message(struct scmi_chan_info *cinfo, /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */ if (res.a0) { - mutex_unlock(&scmi_info->shmem_lock); + smc_channel_lock_release(scmi_info); return -EOPNOTSUPP; } @@ -170,7 +223,7 @@ static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret) { struct scmi_smc *scmi_info = cinfo->transport_info; - mutex_unlock(&scmi_info->shmem_lock); + smc_channel_lock_release(scmi_info); } static const struct scmi_transport_ops scmi_smc_ops = { @@ -196,4 +249,5 @@ const struct scmi_desc scmi_smc_desc = { * from the shared memory area. */ .sync_cmds_atomic_replies = true, + .atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE), };