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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61058C433EF for ; Wed, 17 Nov 2021 20:29:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EA1C6124B for ; Wed, 17 Nov 2021 20:29:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232051AbhKQUcH (ORCPT ); Wed, 17 Nov 2021 15:32:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:40342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230461AbhKQUcB (ORCPT ); Wed, 17 Nov 2021 15:32:01 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E12726101C; Wed, 17 Nov 2021 20:29:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637180942; bh=E7Xqx7+Vg8jNNUkoeKrmpbXyXZbGKa01vFND7BArLlM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IhSHNeA2YN0FvdEVHehRjIvHU6XVmRc5K0M8q4V1PtI1cNigkxf5CnzKPV8z66amU zu9KjXxwSiWnJwvr9Zu/NCReh/eN/rovh4aymEMTopxBZp9H7/DZFtiUHjf191AjdB aDbQiFZ43+Xyo/jyKc+gN8J71D/L/eCpjCBSXwW+7tjr9idecMfs0re61teRhMMlfD eD29mMM6461M6c5Ox4XnMcflMMoONd0PjGaX44Q+q/e+yX+8zcAum977wTB8jKhDqK C1iDw/Sg8Mynmh5KGv/Z9VpIG1FYl4n1ditx8dLjcsjxNokhZjXGcQs595u89KhLaw MZWvHqQSP96+Q== Received: by pali.im (Postfix) id 6DDC145C; Wed, 17 Nov 2021 21:28:59 +0100 (CET) Date: Wed, 17 Nov 2021 21:28:59 +0100 From: Pali =?utf-8?B?Um9ow6Fy?= To: Bjorn Helgaas Cc: Marc Zyngier , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, kernel-team@android.com, Alyssa Rosenzweig , Lorenzo Pieralisi , Bjorn Helgaas Subject: Re: [PATCH] PCI: apple: Reset the port for 100ms on probe Message-ID: <20211117202859.2m5sqwz6xsjgldji@pali> References: <20211117160053.232158-1-maz@kernel.org> <20211117201245.GA1768803@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211117201245.GA1768803@bhelgaas> User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! On Wednesday 17 November 2021 14:12:45 Bjorn Helgaas wrote: > [+cc Pali] > > On Wed, Nov 17, 2021 at 04:00:53PM +0000, Marc Zyngier wrote: > > While the Apple PCIe driver works correctly when directly booted > > from the firmware, it fails to initialise when the kernel is booted > > from a bootloader using PCIe such as u-boot. > > > > That's beacuse we're missing a proper reset of the port (we only > > clear the reset, but never assert it). > > s/beacuse/because/ > > > Bring the port back to life by wiggling the #PERST pin for 100ms > > (as per the spec). > > I cc'd Pali because I think he's interested in consolidating or > somehow rationalizing delays like this. > > If we have a specific spec reference here, I think it would help that > effort. I *think* it's PCIe r5.0, sec 6.6.1, which mentions the 100ms > along with some additional constraints, like waiting 100ms after Link > training completes for ports that support > 5.0 GT/s, whether > Readiness Notifications are used, and CRS Software Visiblity. This is not 100ms timeout "after link training completes". Timeout in this patch is between flipping PERST# signal, so timeout means how long needs to be endpoint card in reset state. And this timeout cannot be controller specific. In past I have tried to find this timeout in specifications, I was not able. Some summary is in my email: https://lore.kernel.org/linux-pci/20210310110535.zh4pnn4vpmvzwl5q@pali/ So I would like to know, why was chosen 100ms for msleep() in this patch? > > Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up") > > Signed-off-by: Marc Zyngier > > Cc: Alyssa Rosenzweig > > Cc: Lorenzo Pieralisi > > Cc: Bjorn Helgaas > > --- > > drivers/pci/controller/pcie-apple.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c > > index 1bf4d75b61be..bbea5f6e0a68 100644 > > --- a/drivers/pci/controller/pcie-apple.c > > +++ b/drivers/pci/controller/pcie-apple.c > > @@ -543,6 +543,9 @@ static int apple_pcie_setup_port(struct apple_pcie *pcie, > > if (ret < 0) > > return ret; > > > > + /* Hold #PERST for 100ms as per the spec */ > > + gpiod_set_value(reset, 0); > > + msleep(100); > > rmw_set(PORT_PERST_OFF, port->base + PORT_PERST); > > gpiod_set_value(reset, 1); > > > > -- > > 2.30.2 > >