From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7D5E153BE4 for ; Wed, 12 Jun 2024 07:50:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718178649; cv=none; b=LGW/oQnyTYhKccRDqGr8THkNggytv2/lWBIFv5jwhrwh6YkOJFVCvZQJmoSdMyC40sEATiIpfNOjTS3rml6QQ22WEihYEgQdah4ZEJzv8NJHjPbDyjPBue9G8mZTtc5XWVWetGQXN6FSV9/nJjPxDQfHlcUrJYdlyPc5lCovigE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718178649; c=relaxed/simple; bh=6j5nmVN4/w954+EEjbFJDKGz9HKp0nWVC4rClE8nQ8M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tHGSClXCuinuONL1PaaL2NKLSaQsizCZ5aaTOcElLZcVtwUmqG9JCKjFqSKl2XPamrPbcivhs1SoFZlLLxxYc5FdyS0nP8yy6m7oaW3P8X7Vlgg5za74cWit84VaejmcEIa2ld9bmlXCy91YRqo2Jd9hUoRfnuaGYVaRop3R+Dg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=c43JDqBV; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="c43JDqBV" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718178646; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=a6GIpVOdJiR3MRab3lILOz+mNYVouRDpopjjgMvEJfs=; b=c43JDqBVakoTwITnJONUD7LyRDoGP35AtOEvIh0Y3M9YocXp6wCUaxU3y5T/SUr5uVJXWO 40f2iJawmcacSTPBCSNG8yAUaaQlmA+1/O3cr78Fd45IshGqo1eDV+y0BL8CN+YOsbeaIT G0xnPOTj8GyZe4HVisx1It5BhwyWpcU= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-117-DoC-gBKDNa-qxr4Nxyi01Q-1; Wed, 12 Jun 2024 03:50:39 -0400 X-MC-Unique: DoC-gBKDNa-qxr4Nxyi01Q-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C688F19560B2; Wed, 12 Jun 2024 07:50:37 +0000 (UTC) Received: from localhost (unknown [10.43.135.229]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4E1A119560AF; Wed, 12 Jun 2024 07:50:35 +0000 (UTC) Date: Wed, 12 Jun 2024 09:50:26 +0200 From: Miroslav Lichvar To: Richard Cochran Cc: =?iso-8859-1?B?Q3Pza+FzLA==?= Bence , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org, =?iso-8859-1?Q?Szentendrei=2C_Tam=E1s?= , Alexandre Belloni Subject: Re: [RFC PATCH v2] rtc: pcf2127: Add PPS capability through Seconds Interrupt Message-ID: References: <20240611150458.684349-1-csokas.bence@prolan.hu> Precedence: bulk X-Mailing-List: linux-rtc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 On Tue, Jun 11, 2024 at 10:06:39PM -0700, Richard Cochran wrote: > On Tue, Jun 11, 2024 at 05:04:57PM +0200, Csókás, Bence wrote: > > > PCF2127/29/31 is capable of generating an interrupt on every > > second (SI) or minute (MI) change. It signals this through > > the Minute/Second Flag (MSF) as well, which needs to be cleared. > > This is a RFC, and my comment is that a PPS from an RTC is not useful > to the Linux kernel. I think a TCXO-based RTC can be useful to user space to improve holdover performance with NTP/PTP. There already is the RTC_UIE_ON ioctl to enable interrupts and receive them in user space. The advantage of the PPS device over the ioctl would be more accurate timestamping (kernel vs user-space). Should PPS be supported, it would be nice if it worked generally with all drivers that support RTC_UIE_ON. -- Miroslav Lichvar