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 CA3C7C10DCE for ; Thu, 12 Mar 2020 20:57:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97456206B7 for ; Thu, 12 Mar 2020 20:57:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727041AbgCLU5c (ORCPT ); Thu, 12 Mar 2020 16:57:32 -0400 Received: from foss.arm.com ([217.140.110.172]:41538 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726246AbgCLU5c (ORCPT ); Thu, 12 Mar 2020 16:57:32 -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 4463331B; Thu, 12 Mar 2020 13:57:31 -0700 (PDT) Received: from [10.37.12.40] (unknown [10.37.12.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C8F663F6CF; Thu, 12 Mar 2020 13:57:29 -0700 (PDT) Subject: Re: [PATCH v4 07/13] firmware: arm_scmi: Add notification dispatch and delivery To: Cristian Marussi , 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: Lukasz Luba Message-ID: Date: Thu, 12 Mar 2020 20:57:28 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed 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 3/12/20 7:24 PM, Cristian Marussi wrote: > 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 Yes, your are right, no other IRQ will show up for this channel till we exit mailbox rx callback and clean the bits. > 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 >>> >>> >