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 X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C7078C10DCE for ; Thu, 12 Mar 2020 19:24:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7CD52067C for ; Thu, 12 Mar 2020 19:24:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726853AbgCLTYo (ORCPT ); Thu, 12 Mar 2020 15:24:44 -0400 Received: from foss.arm.com ([217.140.110.172]:40440 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726594AbgCLTYo (ORCPT ); Thu, 12 Mar 2020 15:24:44 -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 930EF31B; Thu, 12 Mar 2020 12:24:43 -0700 (PDT) Received: from [10.1.197.50] (e120937-lin.cambridge.arm.com [10.1.197.50]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C81523F67D; Thu, 12 Mar 2020 12:24:42 -0700 (PDT) Subject: Re: [PATCH v4 07/13] firmware: arm_scmi: Add notification dispatch and delivery To: Lukasz Luba , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: sudeep.holla@arm.com, james.quinlan@broadcom.com, Jonathan.Cameron@Huawei.com References: <20200304162558.48836-1-cristian.marussi@arm.com> <20200304162558.48836-8-cristian.marussi@arm.com> <45d4aee9-57df-6be9-c176-cf0d03940c21@arm.com> From: Cristian Marussi Message-ID: Date: Thu, 12 Mar 2020 19:24:41 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/03/2020 14:06, Lukasz Luba wrote: > > > On 3/12/20 1:51 PM, Lukasz Luba wrote: >> Hi Cristian, >> Hi Lukasz >> just one comment below... >> >> On 3/4/20 4:25 PM, Cristian Marussi wrote: >>> Add core SCMI Notifications dispatch and delivery support logic which is >>> able, at first, to dispatch well-known received events from the RX ISR to >>> the dedicated deferred worker, and then, from there, to final deliver the >>> events to the registered users' callbacks. >>> >>> Dispatch and delivery is just added here, still not enabled. >>> >>> Signed-off-by: Cristian Marussi >>> --- >>> V3 --> V4 >>> - dispatcher now handles dequeuing of events in chunks (header+payload): >>>    handling of these in_flight events let us remove one unneeded memcpy >>>    on RX interrupt path (scmi_notify) >>> - deferred dispatcher now access their own per-protocol handlers' table >>>    reducing locking contention on the RX path >>> V2 --> V3 >>> - exposing wq in sysfs via WQ_SYSFS >>> V1 --> V2 >>> - splitted out of V1 patch 04 >>> - moved from IDR maps to real HashTables to store event_handlers >>> - simplified delivery logic >>> --- >>>   drivers/firmware/arm_scmi/notify.c | 334 ++++++++++++++++++++++++++++- >>>   drivers/firmware/arm_scmi/notify.h |   9 + >>>   2 files changed, 342 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/firmware/arm_scmi/notify.c >>> b/drivers/firmware/arm_scmi/notify.c >> >> [snip] >> >>> + >>> +/** >>> + * scmi_notify  - Queues a notification for further deferred processing >>> + * >>> + * This is called in interrupt context to queue a received event for >>> + * deferred processing. >>> + * >>> + * @handle: The handle identifying the platform instance from which the >>> + *        dispatched event is generated >>> + * @proto_id: Protocol ID >>> + * @evt_id: Event ID (msgID) >>> + * @buf: Event Message Payload (without the header) >>> + * @len: Event Message Payload size >>> + * @ts: RX Timestamp in nanoseconds (boottime) >>> + * >>> + * Return: 0 on Success >>> + */ >>> +int scmi_notify(const struct scmi_handle *handle, u8 proto_id, u8 >>> evt_id, >>> +        const void *buf, size_t len, u64 ts) >>> +{ >>> +    struct scmi_registered_event *r_evt; >>> +    struct scmi_event_header eh; >>> +    struct scmi_notify_instance *ni = handle->notify_priv; >>> + >>> +    /* Ensure atomic value is updated */ >>> +    smp_mb__before_atomic(); >>> +    if (unlikely(!atomic_read(&ni->enabled))) >>> +        return 0; >>> + >>> +    r_evt = SCMI_GET_REVT(ni, proto_id, evt_id); >>> +    if (unlikely(!r_evt)) >>> +        return -EINVAL; >>> + >>> +    if (unlikely(len > r_evt->evt->max_payld_sz)) { >>> +        pr_err("SCMI Notifications: discard badly sized message\n"); >>> +        return -EINVAL; >>> +    } >>> +    if (unlikely(kfifo_avail(&r_evt->proto->equeue.kfifo) < >>> +             sizeof(eh) + len)) { >>> +        pr_warn("SCMI Notifications: queue full dropping proto_id:%d >>> evt_id:%d  ts:%lld\n", >>> +            proto_id, evt_id, ts); >>> +        return -ENOMEM; >>> +    } >>> + >>> +    eh.timestamp = ts; >>> +    eh.evt_id = evt_id; >>> +    eh.payld_sz = len; >>> +    kfifo_in(&r_evt->proto->equeue.kfifo, &eh, sizeof(eh)); >>> +    kfifo_in(&r_evt->proto->equeue.kfifo, buf, len); >>> +    queue_work(r_evt->proto->equeue.wq, >>> +           &r_evt->proto->equeue.notify_work); >> >> Is it safe to ignore the return value from the queue_work here? > > and also from the kfifo_in > kfifo_in returns the number of effectively written bytes (using __kfifo_in), possibly capped to the effectively maximum available space in the fifo, BUT since I absolutely cannot afford to write an incomplete/truncated event into the queue, I check that in advance and backout on queue full: if (unlikely(kfifo_avail(&r_evt->proto->equeue.kfifo) < sizeof(eh) + len)) { return -ENOMEM; and given that the ISR scmi_notify() is the only possible writer on this queue I can be sure that the kfifo_in() will succeed in writing the required number of bytes after the above check...so I don't need to check the return value. Regards Cristian >> >> Regards, >> Lukasz >> >>