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[23.128.96.18]) by mx.google.com with ESMTP id r15si5512677jap.43.2021.07.12.09.28.31; Mon, 12 Jul 2021 09:28:43 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234224AbhGLQaA (ORCPT + 99 others); Mon, 12 Jul 2021 12:30:00 -0400 Received: from foss.arm.com ([217.140.110.172]:58038 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234121AbhGLQ3v (ORCPT ); Mon, 12 Jul 2021 12:29:51 -0400 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 53C6431B; Mon, 12 Jul 2021 09:27:02 -0700 (PDT) Received: from e120937-lin.home (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 86AD63F774; Mon, 12 Jul 2021 09:27:00 -0700 (PDT) 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 v3 8/8] [RFC] firmware: arm_scmi: Make smc transport atomic Date: Mon, 12 Jul 2021 17:26:25 +0100 Message-Id: <20210712162626.34705-9-cristian.marussi@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210712162626.34705-1-cristian.marussi@arm.com> References: <20210712162626.34705-1-cristian.marussi@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Substitute mutex usages with busy-waiting and declare smc transport as .atomic_capable. Signed-off-by: Cristian Marussi --- drivers/firmware/arm_scmi/smc.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c index ec895a82a9ad..8c6e21b04767 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 +15,7 @@ #include #include #include +#include #include #include "common.h" @@ -23,14 +25,15 @@ * * @cinfo: SCMI channel info * @shmem: Transmit/Receive shared memory area - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area * @func_id: smc/hvc call function id */ struct scmi_smc { struct scmi_chan_info *cinfo; struct scmi_shared_mem __iomem *shmem; - struct mutex shmem_lock; +#define INFLIGHT_NONE MSG_TOKEN_MAX + atomic_t inflight; u32 func_id; }; @@ -115,7 +118,7 @@ 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); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); cinfo->transport_info = scmi_info; return 0; @@ -134,6 +137,15 @@ static int smc_chan_free(int id, void *p, void *data) return 0; } +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; +} + static int smc_send_message(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer) { @@ -141,17 +153,18 @@ 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); + spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight)); + shmem_tx_prepare(scmi_info->shmem, xfer); arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res); /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */ if (res.a0) { - mutex_unlock(&scmi_info->shmem_lock); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); return -EOPNOTSUPP; } @@ -170,7 +183,7 @@ 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); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); } static bool @@ -196,4 +209,5 @@ const struct scmi_desc scmi_smc_desc = { .max_rx_timeout_ms = 30, .max_msg = 20, .max_msg_size = 128, + .atomic_capable = true, }; -- 2.17.1