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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F174C433EF for ; Wed, 13 Apr 2022 09:57:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234785AbiDMJ7f (ORCPT ); Wed, 13 Apr 2022 05:59:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231252AbiDMJ7a (ORCPT ); Wed, 13 Apr 2022 05:59:30 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BA8056418 for ; Wed, 13 Apr 2022 02:57:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 39D59B82161 for ; Wed, 13 Apr 2022 09:57:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5853BC385A4; Wed, 13 Apr 2022 09:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649843826; bh=Gvg7LRw/xZeBOxZ+ML/w+hzH8H2F8QR6fA7vJj6buX4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UtLOsXFywpemB7ZRATqgftGYZ2fEWxqCgcGuxcXQw4snvYCkDAhuUINIOxLb9b4aU tqRfgkDGx/y7+jlGaHviy/A6MwxssuD+JFltbSeGrnGLtrDF1TQnzeDhePU/W4xRAq Zd6NLWviWanUiFhp80yq14A1rRthHvVqjkaEcWIMUXH6Mr7mQxBg+MtNDYJFq7AwVw XYAcy5Mq3i23R6aGWno+L9/mmAeOtD9QPwHZWQBLBsGnyxHMnYJeHi2VbpvgyEqVrC ySu5hAoxch9aSVNu3NqrOMLwUbyj/JzryEan+0+XEPIyI+ZrIhXBp6njMIJuWFvzcY +5vDvtXeBm5vw== Date: Wed, 13 Apr 2022 15:27:03 +0530 From: Vinod Koul To: Swapnil Jakhade Cc: kishon@ti.com, linux-phy@lists.infradead.org, linux-kernel@vger.kernel.org, mparab@cadence.com, a-govindraju@ti.com Subject: Re: [PATCH] phy: cadence: Sierra: Add TI J721E specific PCIe multilink lane configuration Message-ID: References: <20220303055026.24899-1-sjakhade@cadence.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220303055026.24899-1-sjakhade@cadence.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03-03-22, 06:50, Swapnil Jakhade wrote: > This patch adds workaround for TI J721E errata i2183 > (https://www.ti.com/lit/er/sprz455a/sprz455a.pdf). > PCIe fails to link up if SERDES lanes not used by PCIe are assigned to > another protocol. For example, link training fails if lanes 2 and 3 are > assigned to another protocol while lanes 0 and 1 are used for PCIe to > form a two lane link. This failure is due to an incorrect tie-off on an > internal status signal indicating electrical idle. > > Status signals going from SERDES to PCIe Controller are tied-off when a > lane is not assigned to PCIe. Signal indicating electrical idle is > incorrectly tied-off to a state that indicates non-idle. As a result, > PCIe sees unused lanes to be out of electrical idle and this causes > LTSSM to exit Detect.Quiet state without waiting for 12ms timeout to > occur. If a receiver is not detected on the first receiver detection > attempt in Detect.Active state, LTSSM goes back to Detect.Quiet and > again moves forward to Detect.Active state without waiting for 12ms as > required by PCIe base specification. Since wait time in Detect.Quiet is > skipped, multiple receiver detect operations are performed back-to-back > without allowing time for capacitance on the transmit lines to > discharge. This causes subsequent receiver detection to always fail even > if a receiver gets connected eventually. > > The workaround only works for 1-lane PCIe configuration. This workaround > involves enabling receiver detect override by setting TX_RCVDET_OVRD_PREG_j > register of the lane running PCIe to 0x2. This causes SERDES to indicate > successful receiver detect when LTSSM is in Detect.Active state, whether a > receiver is actually present or not. If the receiver is present, LTSSM > proceeds to link up as expected. However if receiver is not present, LTSSM > will time out in Polling.Configuration substate since the expected training > sequence packets will not be received. Applied, thanks -- ~Vinod