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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C983C49ED6 for ; Tue, 10 Sep 2019 13:58:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E48821019 for ; Tue, 10 Sep 2019 13:58:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731700AbfIJN6R (ORCPT ); Tue, 10 Sep 2019 09:58:17 -0400 Received: from foss.arm.com ([217.140.110.172]:35820 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726634AbfIJN6R (ORCPT ); Tue, 10 Sep 2019 09:58:17 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3C15B28; Tue, 10 Sep 2019 06:58:16 -0700 (PDT) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A7B3E3F59C; Tue, 10 Sep 2019 06:58:15 -0700 (PDT) Date: Tue, 10 Sep 2019 14:58:13 +0100 From: Andrew Murray To: Pankaj Dubey Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, jingoohan1@gmail.com, gustavo.pimentel@synopsys.com, lorenzo.pieralisi@arm.com, bhelgaas@google.com, Anvesh Salveru Subject: Re: [PATCH 1/2] PCI: dwc: Add support to disable GEN3 equalization Message-ID: <20190910135813.GK9720@e119886-lin.cambridge.arm.com> References: <1568118302-10505-1-git-send-email-pankaj.dubey@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1568118302-10505-1-git-send-email-pankaj.dubey@samsung.com> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 10, 2019 at 05:55:01PM +0530, Pankaj Dubey wrote: > From: Anvesh Salveru > > In some platforms, PCIe PHY may have issues which will prevent linkup > to happen in GEN3 or high speed. In case equalization fails, link will > fallback to GEN1. When you refer to "high speed", do you mean "higher speeds" as in GEN3, GEN4, etc? > > Designware controller has support for disabling GEN3 equalization if > required. This patch enables the designware driver to disable the PCIe > GEN3 equalization by writing into PCIE_PORT_GEN3_RELATED. Thus limiting to GEN2 speeds max, right? Is the purpose of PORT_LOGIC_GEN3_EQ_DISABLE to disable GEN3 and above even though we advertise GEN3 and above speeds? I.e. the IP advertises GEN3 but the phy can't handle it, we can't change what the IP advertises and so we disable equalization to limit to GEN2? I notice many of the other dwc drivers (dra7xx, keystone, tegra194, imx6) seem to use the device tree to specify a max-link-speed and then impose that limit by changing the value in PCI_EXP_LNKCAP. Is your PORT_LOGIC_GEN3_EQ_DISABLE approach and alternative to the PCI_EXP_LNKCAP approach, or does your approach add something else? > > Platform drivers can disable equalization by setting the dwc_pci_quirk > flag DWC_EQUALIZATION_DISABLE. > > Signed-off-by: Anvesh Salveru > Signed-off-by: Pankaj Dubey > --- > drivers/pci/controller/dwc/pcie-designware.c | 7 +++++++ > drivers/pci/controller/dwc/pcie-designware.h | 7 +++++++ > 2 files changed, 14 insertions(+) > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > index 7d25102..bf82091 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -466,4 +466,11 @@ void dw_pcie_setup(struct dw_pcie *pci) > break; > } > dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, val); > + > + val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED); > + > + if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) > + val |= PORT_LOGIC_GEN3_EQ_DISABLE; > + > + dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val); The problem here is that even when DWC_EQUALIZATION_DISABLE is not set the driver will read and write PCIE_PORT_GEN3_RELATED when it is not needed. How about something like: > + > + if (pci->dwc_pci_quirk & DWC_EQUALIZATION_DISABLE) { > + val = dw_pcie_readl_dbi(pci, PCIE_PORT_GEN3_RELATED); > + val |= PORT_LOGIC_GEN3_EQ_DISABLE; > + dw_pcie_writel_dbi(pci, PCIE_PORT_GEN3_RELATED, val); > + } > } > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index ffed084..a1453c5 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -29,6 +29,9 @@ > #define LINK_WAIT_MAX_IATU_RETRIES 5 > #define LINK_WAIT_IATU 9 > > +/* Parameters for PCIe Quirks */ > +#define DWC_EQUALIZATION_DISABLE 0x1 How about using BIT(1) instead? Thus implying that you can combine quirks. Thanks, Andrew Murray > + > /* Synopsys-specific PCIe configuration registers */ > #define PCIE_PORT_LINK_CONTROL 0x710 > #define PORT_LINK_MODE_MASK GENMASK(21, 16) > @@ -60,6 +63,9 @@ > #define PCIE_MSI_INTR0_MASK 0x82C > #define PCIE_MSI_INTR0_STATUS 0x830 > > +#define PCIE_PORT_GEN3_RELATED 0x890 > +#define PORT_LOGIC_GEN3_EQ_DISABLE BIT(16) > + > #define PCIE_ATU_VIEWPORT 0x900 > #define PCIE_ATU_REGION_INBOUND BIT(31) > #define PCIE_ATU_REGION_OUTBOUND 0 > @@ -244,6 +250,7 @@ struct dw_pcie { > struct dw_pcie_ep ep; > const struct dw_pcie_ops *ops; > unsigned int version; > + unsigned int dwc_pci_quirk; > }; > > #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp) > -- > 2.7.4 >