From owner-freebsd-arm@freebsd.org Tue Aug 20 11:50:58 2019 Return-Path: Delivered-To: freebsd-arm@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 14196CF443 for ; Tue, 20 Aug 2019 11:50:58 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (turbocat.net [IPv6:2a01:4f8:c17:6c4b::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 46CTdY10Gzz4FwH; Tue, 20 Aug 2019 11:50:56 +0000 (UTC) (envelope-from hps@selasky.org) Received: from hps2016.home.selasky.org (unknown [62.141.129.235]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id 2C024260295; Tue, 20 Aug 2019 13:50:49 +0200 (CEST) Subject: Re: Is it a good idea to use a usb-serial adapter for PPS? Yes, it is. To: Per Hedeland , Ian Lepore Cc: freebsd-arm@freebsd.org References: <69a9bed3-4d0a-f8f6-91af-a8f7d84ee307@hedeland.org> <345bae77417c2495f55799b4c7ca2784f4ece9ed.camel@freebsd.org> <7312032d-2908-9414-0445-6b442c3a02e5@hedeland.org> <523b6f0a0fa5f2aeec298fa74df25d3c4af66acc.camel@freebsd.org> <0426fc8b-5398-d8ab-561e-7823c24403a5@hedeland.org> <24b0eaf25b64d6098b390df092866c69e352d859.camel@freebsd.org> <16c91be1-6f2a-b26d-22c7-be8e4ba8eec0@hedeland.org> <72a964c78cbfc36be2345919633ca2196f0783e3.camel@freebsd.org> <540c8b5f-5e81-b67b-4a00-49b86044efe0@selasky.org> <8e28c96e-92c6-5beb-277f-0876a5aba272@hedeland.org> From: Hans Petter Selasky Message-ID: Date: Tue, 20 Aug 2019 13:50:08 +0200 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <8e28c96e-92c6-5beb-277f-0876a5aba272@hedeland.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 46CTdY10Gzz4FwH X-Spamd-Bar: ----- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of hps@selasky.org designates 2a01:4f8:c17:6c4b::2 as permitted sender) smtp.mailfrom=hps@selasky.org X-Spamd-Result: default: False [-5.85 / 15.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; R_SPF_ALLOW(-0.20)[+a:mail.turbocat.net]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[selasky.org]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_HAM_SHORT(-0.96)[-0.964,0]; IP_SCORE(-2.58)[ip: (-9.11), ipnet: 2a01:4f8::/29(-1.95), asn: 24940(-1.85), country: DE(-0.01)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/29, country:DE]; MID_RHS_MATCH_FROM(0.00)[]; SUBJECT_HAS_QUESTION(0.00)[]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Aug 2019 11:50:58 -0000 On 2019-08-20 13:38, Per Hedeland wrote: > > I'm sorry, I'm afraid I still don't really understand... The question, > at least in my mind, was whether polling was done in a "strictly > periodic" fashion, at most once per 125 us for USB 2.0 - or whether > the host controller would poll "as fast as it could", which could > result in a *much* higher polling rate. That depends on the endpoint type. INTERRUPT endpoints poll regularly, one time, every 125 us for example, when a job is queued. BULK endpoints poll all the time, depending a bit on the HC in use. Anyways, the computer is not notified of the completion before the HC is generating an interrupt. This usually happens at some fixed point in time. I.E. multiple completions can be joined into one HC interrupt. It is the completion interrupt which notifies the software about the PPS event. --HPS