From patchwork Mon Nov 22 23:06:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cristian Marussi X-Patchwork-Id: 12693399 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 5F8A1C433F5 for ; Mon, 22 Nov 2021 23:26:52 +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=97On72D8BIrfnD/Rp3U9PONniprhZASzVDXdx6Sy/LE=; b=3H8EnsFDpgxbSe qEtEUkuE6kzPyEz5bMnlY1tXdTibfL0QegwO5LlxG7sEtOFsXmirV5cGeHKit1e46I6rgROki6MHR +iKBcOjqrjKID5POpRUw6ReB7fPf9dR4LceiBD2/HI2vCjFe1a06A/STfTU/1ZedgDm/Fk4vs6e3B W75Y1TMOKKnvpLIhy12KWtdgwvGZc9EPp5nFya8pxhIKt1zm/sfH1lgnJ8pmYgjpn67JfISy4RBNe I1PVAitX3tk3FqKaUzoS8I4h5rDSNd1r9vOo1uG9ytfXBniCtDC49wG4Q54kkwV5MmaaeNqtjlbB5 i1Gr774ahlU0WiOXzjQw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mpIga-000Pjs-QX; Mon, 22 Nov 2021 23:25:21 +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 1mpIPJ-000Jfm-E7 for linux-arm-kernel@lists.infradead.org; Mon, 22 Nov 2021 23:07:31 +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 171F313A1; Mon, 22 Nov 2021 15:07:29 -0800 (PST) Received: from e120937-lin.home (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0CE403F5A1; Mon, 22 Nov 2021 15:07:26 -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, vincent.guittot@linaro.org, souvik.chakravarty@arm.com, cristian.marussi@arm.com, "Michael S. Tsirkin" , Igor Skalkin , Peter Hilber , virtualization@lists.linux-foundation.org Subject: [PATCH v6 14/16] firmware: arm_scmi: Add atomic mode support to virtio transport Date: Mon, 22 Nov 2021 23:06:38 +0000 Message-Id: <20211122230640.1345-15-cristian.marussi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211122230640.1345-1-cristian.marussi@arm.com> References: <20211122230640.1345-1-cristian.marussi@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211122_150729_643277_700D6483 X-CRM114-Status: GOOD ( 32.66 ) 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 support for .mark_txdone and .poll_done transport operations to SCMI VirtIO transport as pre-requisites to enable atomic operations. Add a Kernel configuration option to enable SCMI VirtIO transport polling and atomic mode for selected SCMI transactions while leaving it default disabled. Cc: "Michael S. Tsirkin" Cc: Igor Skalkin Cc: Peter Hilber Cc: virtualization@lists.linux-foundation.org Signed-off-by: Cristian Marussi --- drivers/firmware/arm_scmi/Kconfig | 15 ++ drivers/firmware/arm_scmi/virtio.c | 212 +++++++++++++++++++++++++++-- 2 files changed, 214 insertions(+), 13 deletions(-) diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig index d429326433d1..7794bd41eaa0 100644 --- a/drivers/firmware/arm_scmi/Kconfig +++ b/drivers/firmware/arm_scmi/Kconfig @@ -118,6 +118,21 @@ config ARM_SCMI_TRANSPORT_VIRTIO_VERSION1_COMPLIANCE the ones implemented by kvmtool) and let the core Kernel VirtIO layer take care of the needed conversions, say N. +config ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + bool "Enable atomic mode for SCMI VirtIO transport" + depends on ARM_SCMI_TRANSPORT_VIRTIO + help + Enable support of atomic operation for SCMI VirtIO based transport. + + If you want the SCMI VirtIO 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. + endif #ARM_SCMI_PROTOCOL config ARM_SCMI_POWER_DOMAIN diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c index fd0f6f91fc0b..3101024751b0 100644 --- a/drivers/firmware/arm_scmi/virtio.c +++ b/drivers/firmware/arm_scmi/virtio.c @@ -38,6 +38,7 @@ * @vqueue: Associated virtqueue * @cinfo: SCMI Tx or Rx channel * @free_list: List of unused scmi_vio_msg, maintained for Tx channels only + * @pending_cmds_list: List of pre-fetched commands queueud for later processing * @is_rx: Whether channel is an Rx channel * @ready: Whether transport user is ready to hear about channel * @max_msg: Maximum number of pending messages for this channel. @@ -49,6 +50,9 @@ struct scmi_vio_channel { struct virtqueue *vqueue; struct scmi_chan_info *cinfo; struct list_head free_list; +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + struct list_head pending_cmds_list; +#endif bool is_rx; bool ready; unsigned int max_msg; @@ -65,12 +69,22 @@ struct scmi_vio_channel { * @input: SDU used for (delayed) responses and notifications * @list: List which scmi_vio_msg may be part of * @rx_len: Input SDU size in bytes, once input has been received + * @poll_idx: Last used index registered for polling purposes if this message + * transaction reply was configured for polling. + * Note that virtqueue used index is an unsigned 16-bit. + * @poll_lock: Protect access to @poll_idx. */ struct scmi_vio_msg { struct scmi_msg_payld *request; struct scmi_msg_payld *input; struct list_head list; unsigned int rx_len; +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE +#define VIO_MSG_POLL_DONE 0xffffffffUL + unsigned int poll_idx; + /* lock to protect access to poll_idx. */ + spinlock_t poll_lock; +#endif }; /* Only one SCMI VirtIO device can possibly exist */ @@ -104,17 +118,22 @@ static int scmi_vio_feed_vq_rx(struct scmi_vio_channel *vioch, return rc; } +static inline void scmi_vio_feed_vq_tx(struct scmi_vio_channel *vioch, + struct scmi_vio_msg *msg) +{ + /* Here IRQs are assumed to be already disabled by the caller */ + spin_lock(&vioch->lock); + list_add(&msg->list, &vioch->free_list); + spin_unlock(&vioch->lock); +} + static void scmi_finalize_message(struct scmi_vio_channel *vioch, struct scmi_vio_msg *msg) { - if (vioch->is_rx) { + if (vioch->is_rx) scmi_vio_feed_vq_rx(vioch, msg, vioch->cinfo->dev); - } else { - /* Here IRQs are assumed to be already disabled by the caller */ - spin_lock(&vioch->lock); - list_add(&msg->list, &vioch->free_list); - spin_unlock(&vioch->lock); - } + else + scmi_vio_feed_vq_tx(vioch, msg); } static void scmi_vio_complete_cb(struct virtqueue *vqueue) @@ -138,12 +157,29 @@ static void scmi_vio_complete_cb(struct virtqueue *vqueue) goto unlock_ready_out; } +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + /* At first loop on pending_cmd_list of buffered msg if any */ + if (!vioch->is_rx) { + struct scmi_vio_msg *tmp; + + list_for_each_entry_safe(msg, tmp, + &vioch->pending_cmds_list, + list) { + scmi_rx_callback(vioch->cinfo, + msg_read_header(msg->input), + msg); + scmi_vio_feed_vq_tx(vioch, msg); + } + } +#endif + /* IRQs already disabled here no need to irqsave */ spin_lock(&vioch->lock); if (cb_enabled) { virtqueue_disable_cb(vqueue); cb_enabled = false; } + msg = virtqueue_get_buf(vqueue, &length); if (!msg) { if (virtqueue_enable_cb(vqueue)) @@ -257,6 +293,9 @@ static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, GFP_KERNEL); if (!msg->request) return -ENOMEM; +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + spin_lock_init(&msg->poll_lock); +#endif } msg->input = devm_kzalloc(cinfo->dev, VIRTIO_SCMI_MAX_PDU_SIZE, @@ -324,13 +363,23 @@ static int virtio_send_message(struct scmi_chan_info *cinfo, } msg = list_first_entry(&vioch->free_list, typeof(*msg), list); - list_del(&msg->list); + list_del_init(&msg->list); msg_tx_prepare(msg->request, xfer); sg_init_one(&sg_out, msg->request, msg_command_size(xfer)); sg_init_one(&sg_in, msg->input, msg_response_size(xfer)); +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + if (xfer->hdr.poll_completion) { + /* Retrieve last used index and use it as polling reference. */ + spin_lock(&msg->poll_lock); + msg->poll_idx = virtqueue_enable_cb_prepare(vioch->vqueue); + spin_unlock(&msg->poll_lock); + xfer->priv = msg; + } +#endif + rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, msg, GFP_ATOMIC); if (rc) { list_add(&msg->list, &vioch->free_list); @@ -350,10 +399,8 @@ static void virtio_fetch_response(struct scmi_chan_info *cinfo, { struct scmi_vio_msg *msg = xfer->priv; - if (msg) { + if (msg) msg_fetch_response(msg->input, msg->rx_len, xfer); - xfer->priv = NULL; - } } static void virtio_fetch_notification(struct scmi_chan_info *cinfo, @@ -361,11 +408,142 @@ static void virtio_fetch_notification(struct scmi_chan_info *cinfo, { struct scmi_vio_msg *msg = xfer->priv; - if (msg) { + if (msg) msg_fetch_notification(msg->input, msg->rx_len, max_len, xfer); - xfer->priv = NULL; +} + +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE +/** + * virtio_mark_txdone - Mark transmission done + * + * Free successfully completed polling transfer messages. + * + * @cinfo: SCMI channel info + * @ret: Transmission return code + * @xfer: Transfer descriptor + */ +static void virtio_mark_txdone(struct scmi_chan_info *cinfo, int ret, + struct scmi_xfer *xfer) +{ + unsigned long flags; + struct scmi_vio_channel *vioch = cinfo->transport_info; + struct scmi_vio_msg *msg = xfer->priv; + + if (!msg) + return; + + /* Is a successfully polling reply message still to be finalized ? */ + spin_lock_irqsave(&msg->poll_lock, flags); + if (!ret && xfer->hdr.poll_completion && list_empty(&msg->list)) + scmi_vio_feed_vq_tx(vioch, msg); + spin_unlock_irqrestore(&msg->poll_lock, flags); + + xfer->priv = NULL; +} + +/** + * virtio_poll_done - Provide polling support for VirtIO transport + * + * @cinfo: SCMI channel info + * @xfer: Reference to the transfer being poll for. + * + * VirtIO core provides a polling mechanism based only on last used indexes: + * this means that it is possible to poll the virtqueues waiting for something + * new to arrive from the host side but the only way to check if the freshly + * arrived buffer was what we were waiting for is to compare the newly arrived + * message descriptors with the one we are polling on. + * + * As a consequence it can happen to dequeue something different from the buffer + * we were poll-waiting for: if that is the case such early fetched buffers are + * then added to a the @pending_cmds_list list for later processing within the + * usual VirtIO callbacks; so, basically, once something new is spotted we + * proceed to de-queue all the freshly received used buffers until we found the + * one we were polling on, or we empty the virtqueue. + * + * Note that we do NOT suppress notification with VIRTQ_USED_F_NO_NOTIFY even + * when polling since such flag is per-virtqueues and we do not want to + * suppress notifications as a whole: so, if the message we are polling for is + * delivered via usual IRQs callbacks, it will be handled as such and the + * polling loop will be transparently terminated anyway. + * + * Return: True once polling has successfully completed. + */ +static bool virtio_poll_done(struct scmi_chan_info *cinfo, + struct scmi_xfer *xfer) +{ + bool ret; + unsigned long flags; + struct scmi_vio_msg *msg = xfer->priv; + struct scmi_vio_channel *vioch = cinfo->transport_info; + + if (!msg) + return true; + + /* Processed already by other polling on another CPU ? */ + spin_lock_irqsave(&msg->poll_lock, flags); + if (msg->poll_idx == VIO_MSG_POLL_DONE) { + spin_unlock_irqrestore(&msg->poll_lock, flags); + return true; } + + /* Has cmdq index moved at all ? */ + ret = virtqueue_poll(vioch->vqueue, msg->poll_idx); + spin_unlock_irqrestore(&msg->poll_lock, flags); + if (ret) { + struct scmi_vio_msg *next_msg; + + spin_lock_irqsave(&vioch->lock, flags); + virtqueue_disable_cb(vioch->vqueue); + + /* + * If something arrived we cannot be sure if it was the reply to + * the xfer we are polling for some other replies to other, even + * possibly non-polling, pending xfer: process all new messages + * till the polling-for message is found OR the vqueue is empty. + */ + do { + unsigned int length; + + next_msg = virtqueue_get_buf(vioch->vqueue, &length); + if (next_msg) { + next_msg->rx_len = length; + if (next_msg == msg) { + ret = true; + break; + } + + list_add_tail(&next_msg->list, + &vioch->pending_cmds_list); + spin_lock(&next_msg->poll_lock); + next_msg->poll_idx = VIO_MSG_POLL_DONE; + spin_unlock(&next_msg->poll_lock); + ret = false; + } + } while (next_msg); + + /* + * When the polling loop has successfully terminated simply + * restart the vqueue, no matter if something else was queued + * in the meantime, it will be served by normal IRQ/callback. + * + * If we emptied the vqueue but there's still no sign + * of the message we are polling for, update the polling + * index to the current vqueue head. + */ + if (ret) { + virtqueue_enable_cb(vioch->vqueue); + } else { + spin_lock(&msg->poll_lock); + msg->poll_idx = + virtqueue_enable_cb_prepare(vioch->vqueue); + spin_unlock(&msg->poll_lock); + } + spin_unlock_irqrestore(&vioch->lock, flags); + } + + return ret; } +#endif static const struct scmi_transport_ops scmi_virtio_ops = { .link_supplier = virtio_link_supplier, @@ -376,6 +554,10 @@ static const struct scmi_transport_ops scmi_virtio_ops = { .send_message = virtio_send_message, .fetch_response = virtio_fetch_response, .fetch_notification = virtio_fetch_notification, +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + .mark_txdone = virtio_mark_txdone, + .poll_done = virtio_poll_done, +#endif }; static int scmi_vio_probe(struct virtio_device *vdev) @@ -418,6 +600,9 @@ static int scmi_vio_probe(struct virtio_device *vdev) spin_lock_init(&channels[i].lock); spin_lock_init(&channels[i].ready_lock); INIT_LIST_HEAD(&channels[i].free_list); +#ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE + INIT_LIST_HEAD(&channels[i].pending_cmds_list); +#endif channels[i].vqueue = vqs[i]; sz = virtqueue_get_vring_size(channels[i].vqueue); @@ -506,4 +691,5 @@ const struct scmi_desc scmi_virtio_desc = { .max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */ .max_msg = 0, /* overridden by virtio_get_max_msg() */ .max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE, + .atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_VIRTIO_ATOMIC_ENABLE), };