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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DE8ACC5516F for ; Fri, 31 Jul 2026 16:03:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:References: List-Owner; bh=V0cx84YDl6LOig0HnLnRYdR8vDgzvhQjJIOIpIIfTbs=; b=nhTqwoHT1nEIqc qylzG3a+E0ksPpTRdlbYewAF/K2sh0dGfFuuCiPzYs4tkKgms/Vp7wIpOCd0sLNX28c80sA6eCWtj IfQiCZfWFAwtiEAXnzE9N6TBSjAK2MKp7AJ4XqM17xvAZPDOvbdM4sPL+FshWwFpRPo2J97Zbp2gx C8AscVmrRcAnSWY7ElAB+yazMk5a5CxRm60sfNH8e4m5diGndjA/X67u9aaOsP4N1Dfe14DdLTZgD sL4LAqiICD11EWNoKfJXVpGIrvjTrrSUJr7T/6F6cJNYHPA/YxPUnMtTRLZpTzpiT4EChc9qAq37t ug/YpSGAmeJcG8DsBTIA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wpphO-0000000CwrD-2M6n; Fri, 31 Jul 2026 16:03:02 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wpphN-0000000Cwqs-0Rnt for linux-arm-kernel@lists.infradead.org; Fri, 31 Jul 2026 16:03:01 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id C5FD96004E; Fri, 31 Jul 2026 16:02:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49CFF1F00AC4; Fri, 31 Jul 2026 16:02:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785513779; bh=V0cx84YDl6LOig0HnLnRYdR8vDgzvhQjJIOIpIIfTbs=; h=Date:From:To:Cc:Subject:In-Reply-To; b=T/EpjkArdt1UgrmZZjFVnYZknZPxp8v78vrWDVYTN/uHtZ72MakLbuKPkn1azv3kl FaKNPlBsJharLNGbVsO8hm1vaji6oeX03r2KXZCcZtPmdwoQsZiOmka0om6WfUNgRm tkeg48/USHInUNaOpqDlJdUkzVvq50aADNBz++Jcsecaj4SXhqUfZJDJW5MVhNcc6R IALqTbNkKO0M/VE11ldTpe0YLG+gf413/B6dyGukXy+zeSy9x1Fkop1bW11U18b9L8 9cLhOXgH+S/PrAGfEVT9iR9seSc7hP5FIxMldcl+gfWPSAZBA2lQhAaC9zLXVmIc9T 0KyiTzxyyNIjQ== Date: Fri, 31 Jul 2026 11:02:58 -0500 From: Bjorn Helgaas To: hongxing.zhu@oss.nxp.com Cc: frank.li@nxp.com, l.stach@pengutronix.de, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, robh@kernel.org, bhelgaas@google.com, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org, Richard Zhu Subject: Re: [PATCH v4] PCI: imx6: Update MPLLB bandwidth to improve i.MX95 Gen3 PCIe stability Message-ID: <20260731160258.GA1571469@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260731030546.850457-1-hongxing.zhu@oss.nxp.com> X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jul 31, 2026 at 11:05:46AM +0800, hongxing.zhu@oss.nxp.com wrote: > From: Richard Zhu > > Bandwidth marginality was observed during i.MX95 Gen3 PCIe tests with > the default MPLLB_BANDWIDTH value (120). This margin degradation worsens > across voltage and temperature (VT) variations and different test > matrices, potentially causing link stability issues. > > Testing with MPLLB_BANDWIDTH value of 140 (0x8c) shows significant > improvement in bandwidth margins across all VT conditions and test > scenarios. > > Implement PHY register write helper function and configure: > - MPLLB_BW_OVRD_IN = 140 (0x8c) for improved bandwidth margin > - MPLLB_BW_OVRD_EN to enable the override > > This ensures robust PCIe Gen3 performance across all operating > conditions. Thanks for including the previous and new MPLLB_BANDWIDTH values. I'm fine with the patch, but I think "bandwidth marginality" is awkward wording because "marginality" doesn't seem to be commonly used in this context. Maybe something like: We observed poor bandwidth margins during ... The margins worsened across ...