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 B72B7432BCB for ; Tue, 11 Aug 2026 12:22:58 +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=1786450980; cv=none; b=YAeRsmmBIM89rouaaQ4dWB/2GlfPs1r0TIz0VwP5E7Z16XpBQ4yO1IUGTK5JYzsw4dnfgNSfrK4tYXmDMRvrDDPf8XIX2XEmEtYfBaiXB1lO7/0nnCgllPaMdYgqDt/V5xqACOGp2Kw8KbxCtGN2l2KlB0DJH++e6buwZU3BwN8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786450980; c=relaxed/simple; bh=OXjwWaAHCtJe/l1tvo90Y//Wq15ugOpZvjih3gIWlgg=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=oupQE0/BNSq0ph1PAhGTAWPpa6a1IcQpPWUXQqr2FgFBtVP+Vq0S6Xcn4vNbg4/UyYejO5egglO4zdvjoVHaLx115UMNINPMhR6cpPyAQNkuPW+8sc5IRwZYq0s/UmxmAIndcuQjOHhnfxTyMODzs0ZGo8/Z/QSo4wnmlwyfDL8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=PdjyFPjo; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="PdjyFPjo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1786450977; 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=OXjwWaAHCtJe/l1tvo90Y//Wq15ugOpZvjih3gIWlgg=; b=PdjyFPjoCOJmacH20Mth8evF8d6bq6hckUmm+cgQragirIHE+cffP86S38gZOWiaIOqD6/ uz1KSfSl4lxjJbrKYrsLtm/d5swdp7LOFe4/XLyWoJO/hC//GEuUYRrTguGH2nQzbqrBlo avDE+K6y1wZYlrllspPD1f7SjZfgv5w= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-481-h5trJIUWN6WM6DBYAzrkbw-1; Tue, 11 Aug 2026 08:22:43 -0400 X-MC-Unique: h5trJIUWN6WM6DBYAzrkbw-1 X-Mimecast-MFC-AGG-ID: h5trJIUWN6WM6DBYAzrkbw_1786450961 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1BA341800984; Tue, 11 Aug 2026 12:22:41 +0000 (UTC) Received: from [10.43.2.199] (unknown [10.43.2.199]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id EA8EC19560AB; Tue, 11 Aug 2026 12:22:37 +0000 (UTC) Message-ID: <2a02b878-d605-4db4-a9a1-7323beb35e4a@redhat.com> Date: Tue, 11 Aug 2026 14:22:36 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v6 2/3] dpll: zl3073x: add channel ToD, phase step and TIE operations From: Ivan Vecera To: netdev@vger.kernel.org Cc: Petr Oros , Chris du Quesnay , Arkadiusz Kubalewski , Jakub Kicinski , Jiri Pirko , Min Li , Paolo Abeni , Richard Cochran , Vadim Fedorenko , linux-kernel@vger.kernel.org, Jonathan Corbet , Shuah Khan , linux-doc@vger.kernel.org References: <20260809182340.1081610-1-ivecera@redhat.com> <20260809182340.1081610-3-ivecera@redhat.com> Content-Language: en-US In-Reply-To: <20260809182340.1081610-3-ivecera@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Sashiko findings and replies: > Does capturing the post-timestamp here degrade cross-timestamping > precision? [...] > Should the post-timestamp be captured immediately after > zl3073x_chan_tod_ctrl() issues the command? The post-timestamp must be taken after the semaphore clears, not after the command write. The hardware latches the ToD value as part of processing the command, which completes when the semaphore is cleared. Taking the post-timestamp before the wait would risk the window not containing the actual latch event, which would be worse than a wider but correct window. > Could this retry loop exhaust its budget and fail spuriously [...]? Testing shows that a single iteration of the loop body (two ToD reads) takes approximately 17-19 ms. With 20 retries that gives a budget of 340-380 ms, which is more than enough to outlast the 20 ms margin window. After the 1 Hz edge crosses, the next read returns ~980 ms of margin and the loop breaks. > Is it possible for preemption to cause a 1-second clock shift here? The 20 ms threshold provides sufficient margin for the write sequence. This requires ~20 ms of preemption under a held mutex to cause an issue, which is not reachable in practice. Thanks, Ivan