From patchwork Wed Dec 20 17:21:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cristian Marussi X-Patchwork-Id: 13500410 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 93124C3DA6E for ; Wed, 20 Dec 2023 17:22:01 +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:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version: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:In-Reply-To:References: List-Owner; bh=ku/nyxoAPmCwKhO03T+FKjoN+LlIxBNJ2PnBKAZ8Aao=; b=l1pJquNEDeHBhQ djP8EPcwgchASPnz08RbJkqO7X7kw5CAlhvd/x2do/4/Bg7fL1sNEGrAbub4xkcktG2eBbA7ySo74 +NbQeaYKXxXU3cb51OgjsT0C+Se3wBdwAahunW0rzbg3NGqL844KxNnjvK7JA3SpPO+x1SuTtXt4y Jg7og3D/66EKk1mdC8/2HL/Yk7iHDp8jwBeFT+iHUf7ml2ss0WVlfSvGS0LNDzIPyrgCcY/eeAtqx lB1kiHhwSOQviWywH7OwEwdF/1aidtude9gOcfP4PYz0HDUpo12hwn/ClAJ3yGnmBziNB1ZPrhz8h GSex8ZrjtNjO5r6RYlYw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rG0GE-000Zhs-0I; Wed, 20 Dec 2023 17:21:34 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rG0GA-000ZhT-0m for linux-arm-kernel@lists.infradead.org; Wed, 20 Dec 2023 17:21:31 +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 612B61FB; Wed, 20 Dec 2023 09:22:12 -0800 (PST) Received: from e120937-lin.. (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 479663F64C; Wed, 20 Dec 2023 09:21:26 -0800 (PST) From: Cristian Marussi To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: sudeep.holla@arm.com, vincent.guittot@linaro.org, Cristian Marussi , Xinglong Yang , stable@vger.kernel.org Subject: [PATCH] firmware: arm_scmi: Check Mailbox/SMT channel for consistency Date: Wed, 20 Dec 2023 17:21:12 +0000 Message-Id: <20231220172112.763539-1-cristian.marussi@arm.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231220_092130_392993_78773F61 X-CRM114-Status: GOOD ( 15.62 ) 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 reception of a completion interrupt the SMT memory area is accessed to retrieve the message header at first and then, if the message sequence number identifies a transaction which is still pending, the related payload is fetched too. When an SCMI command times out the channel ownership remains with the platform until eventually a late reply is received and, as a consequence, any further transmission attempt remains pending, waiting for the channel to be relinquished by the platform. Once that late reply is received the channel ownership is given back to the agent and any pending request is then allowed to proceed and overwrite the SMT area of the just delivered late reply; then the wait for the reply to the new request starts. It has been observed that the spurious IRQ related to the late reply can be wrongly associated with the freshly enqueued request: when that happens the SCMI stack in-flight lookup procedure is fooled by the fact that the message header now present in the SMT area is related to the new pending transaction, even though the real reply has still to arrive. This race-condition on the A2P channel can be detected by looking at the channel status bits: a genuine reply from the platform will have set the channel free bit before triggering the completion IRQ. Add a consistency check to validate such condition in the A2P ISR. Reported-by: Xinglong Yang Closes: https://lore.kernel.org/all/PUZPR06MB54981E6FA00D82BFDBB864FBF08DA@PUZPR06MB5498.apcprd06.prod.outlook.com/ Fixes: 5c8a47a5a91d ("firmware: arm_scmi: Make scmi core independent of the transport type") CC: stable@vger.kernel.org # 5.15+ Signed-off-by: Cristian Marussi Tested-by: Xinglong Yang --- drivers/firmware/arm_scmi/common.h | 1 + drivers/firmware/arm_scmi/mailbox.c | 14 ++++++++++++++ drivers/firmware/arm_scmi/shmem.c | 6 ++++++ 3 files changed, 21 insertions(+) diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h index 3b7c68a11fd0..0956c2443840 100644 --- a/drivers/firmware/arm_scmi/common.h +++ b/drivers/firmware/arm_scmi/common.h @@ -329,6 +329,7 @@ void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem, void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem); bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem, struct scmi_xfer *xfer); +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem); /* declarations for message passing transports */ struct scmi_msg_payld; diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c index 19246ed1f01f..b8d470417e8f 100644 --- a/drivers/firmware/arm_scmi/mailbox.c +++ b/drivers/firmware/arm_scmi/mailbox.c @@ -45,6 +45,20 @@ static void rx_callback(struct mbox_client *cl, void *m) { struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl); + /* + * An A2P IRQ is NOT valid when received while the platform still has + * the ownership of the channel, because the platform at first releases + * the SMT channel and then sends the completion interrupt. + * + * This addresses a possible race condition in which a spurious IRQ from + * a previous timed-out reply which arrived late could be wrongly + * associated with the next pending transaction. + */ + if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) { + dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n"); + return; + } + scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem), NULL); } diff --git a/drivers/firmware/arm_scmi/shmem.c b/drivers/firmware/arm_scmi/shmem.c index 87b4f4d35f06..517d52fb3bcb 100644 --- a/drivers/firmware/arm_scmi/shmem.c +++ b/drivers/firmware/arm_scmi/shmem.c @@ -122,3 +122,9 @@ bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem, (SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR | SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE); } + +bool shmem_channel_free(struct scmi_shared_mem __iomem *shmem) +{ + return (ioread32(&shmem->channel_status) & + SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE); +}