From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) (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 7423D2FE042; Wed, 6 May 2026 06:22:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778048530; cv=none; b=WBJceMf5fFlLxO0HD3Q7eXfXn4ri2WtbwCGSXMyETe+mQS6a4C5btw4hU/AGCXdiYipKhLL6DnjjvI10VPma6D/0AwZSQlgVA/YTcT2DVcsSE5UOlnyXJGjkQO/ZadMHhL/JSX72eprid/VVnFAfBFYvwQfmTXVBVBPuzXtBKvg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778048530; c=relaxed/simple; bh=tO/P59QFbb2wY0arYKYcGmAulgqF0HwsaPPCzm3PclY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pr2OUG6Ef22yZOmBL1Onee97lz2ldJZZE+gfZYepwZIcxF6AH8cap2m+G1XpFwoqOgJ4Te568piVXJxwXlm8rfgyOOMAugthQy3ZqXM7oPfWN6bgv7L+AZRW3Us1SNivFbhtJ3R8uNAhvliR2ffPjY5y80z2jM76/pvDQ3a2VHQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=lSrXbCAj; arc=none smtp.client-ip=192.198.163.14 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="lSrXbCAj" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1778048529; x=1809584529; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=tO/P59QFbb2wY0arYKYcGmAulgqF0HwsaPPCzm3PclY=; b=lSrXbCAjY30iTzOl1gf+KQYlbb+V8UzwyWXAfOKqbjcY+rKuEQHY4PHI guRyB6UQNk+B9IuphYJamRa3w2DPIT1oqX2QbDc+ltm4B/meo37ASXldn 65duPB7nkeLd4+vlcfQiw8TOBMFxnWBo8Unr1TURFskIVAgezoA9C3V40 K73v6hFGZIop4qFjXnZgGbyTzk4mn716OuivF+WrqURgD4glFgCFOl/0L 3PBu7TbjcehrobUG6mQBEakU0T48YcqnEPL2FvL+4iKYxiIgpRsZNwV6r fQSqrQ9G85P20pjD4hQIOCmxFdAUvv5wP8cqqb3hzNl0uuVhc0KJYGwc7 g==; X-CSE-ConnectionGUID: zhxc+G6ISbKHiHRdI4/HPA== X-CSE-MsgGUID: oXQRMCgET1qgBkpwxbEMxQ== X-IronPort-AV: E=McAfee;i="6800,10657,11777"; a="78993989" X-IronPort-AV: E=Sophos;i="6.23,219,1770624000"; d="scan'208";a="78993989" Received: from orviesa010.jf.intel.com ([10.64.159.150]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2026 23:22:05 -0700 X-CSE-ConnectionGUID: a80tDqs4S5eL7ELXQ5SBGA== X-CSE-MsgGUID: 1usHIHH7QRm7nYQgNoAu2g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,219,1770624000"; d="scan'208";a="235179657" Received: from mohdfai2-mobl.gar.corp.intel.com (HELO [10.247.37.237]) ([10.247.37.237]) by orviesa010-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2026 23:22:02 -0700 Message-ID: <63b186e0-046d-496e-8ae4-d68cd5eb5817@linux.intel.com> Date: Wed, 6 May 2026 14:21:59 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH iwl-next v4 0/3] igc: add support for forcing link speed without autonegotiation To: David Laight , KhaiWenTan Cc: anthony.l.nguyen@intel.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, faizal.abdul.rahim@intel.com, hong.aun.looi@intel.com, khai.wen.tan@intel.com References: <20260428060009.311393-1-khai.wen.tan@linux.intel.com> <20260430154105.505739ac@pumpkin> Content-Language: en-US From: "Abdul Rahim, Faizal" In-Reply-To: <20260430154105.505739ac@pumpkin> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 30/4/2026 10:41 pm, David Laight wrote: > On Tue, 28 Apr 2026 14:00:06 +0800 > KhaiWenTan wrote: > >> From: Faizal Rahim >> >> This series adds support for forcing 10/100 Mb/s link speed via ethtool >> when autonegotiation is disabled on the igc driver. > > I'll ask 'why' ? > > In particular forcing half/full duplex has always been a very good way > of 'breaking' a network connection. > > It really is much better to restrict the advertised link modes and let > the autodetect/autonegotiation logic in the phy/mac do its job. > > About the only think I can think of is to force 10M HDX when connected > to a remote system that supports 10M/100M HDX. > In that case you need to send out single link test pulses, not the > burst used to identify 100M HDX, or the pattern encoded on the burst > used by autonegotiation. > But you need to got back to the mid 1990s to find such systems. > Anything that supports FDX will do autonegotiation. > > David > There's a use case requested: Profinet Certification tool reports that forcing a link speed without auto-negotiation is not working. Forcing the link speed is a critical feature for the industrial automation "fast-start" use case. When there is a connection lost, the system must come back up as fast as possible. In PROFINET, that means to force the speed and rejoin the controller loops. Without supporting forcing the speed to 100M in Foxville, the certification tool would not be able to certify the availability of this feature. I'm hoping this context is enough to justify the need?