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 3B4EEC433F5 for ; Wed, 23 Mar 2022 10:37:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240907AbiCWKi0 (ORCPT ); Wed, 23 Mar 2022 06:38:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243606AbiCWKiN (ORCPT ); Wed, 23 Mar 2022 06:38:13 -0400 X-Greylist: delayed 161215 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 23 Mar 2022 03:36:43 PDT Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::226]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 21CC325E81; Wed, 23 Mar 2022 03:36:42 -0700 (PDT) Received: (Authenticated sender: alex@ghiti.fr) by mail.gandi.net (Postfix) with ESMTPSA id A413EC0006; Wed, 23 Mar 2022 10:36:38 +0000 (UTC) Message-ID: <85e864fd-762e-0780-f829-bfbb178ab24e@ghiti.fr> Date: Wed, 23 Mar 2022 11:36:37 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [V3] PCI: fu740: Drop to 2.5GT/s to fix initial device probing on some boards Content-Language: en-US From: Alexandre Ghiti To: Ben Dooks , linux-pci@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Bjorn Helgaas , Palmer Dabbelt , Rob Herring , Lorenzo Pieralisi , Greentime Hu , Paul Walmsley , "Maciej W. Rozycki" , David Abdurachmanov References: <20220318152430.526320-1-ben.dooks@codethink.co.uk> <2442936e-a53e-59bf-488f-95eac26d1252@ghiti.fr> In-Reply-To: <2442936e-a53e-59bf-488f-95eac26d1252@ghiti.fr> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 3/21/22 14:49, Alexandre Ghiti wrote: > Hi Ben, > > On 3/18/22 16:24, Ben Dooks wrote: >> The fu740 PCIe core does not probe any devices on the SiFive Unmatched >> board without this fix (or having U-Boot explicitly start the PCIe via >> either boot-script or user command). The fix is to start the link at >> 2.5GT/s speeds and once the link is up then change the maximum speed >> back >> to the default. >> >> The U-Boot driver claims to set the link-speed to 2.5GT/s to get the >> probe >> to work (and U-Boot does print link up at 2.5GT/s) in the following >> code: >> https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/pci/pcie_dw_sifive.c?id=v2022.01#L271 >> >> >> Signed-off-by: Ben Dooks >> -- >> Note, this patch has had significant re-work since the previous 4 >> sets, including trying to fix style, message, reliance on the U-Boot >> fix and the comments about usage of LINK_CAP and reserved fields. >> >> v2: >> - fix issues with Gen1/2.5GTs >> - updated comment on the initial probe >> - run tests with both uninitialised and initialsed pcie from uboot >> --- >>   drivers/pci/controller/dwc/pcie-fu740.c | 52 ++++++++++++++++++++++++- >>   1 file changed, 51 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/controller/dwc/pcie-fu740.c >> b/drivers/pci/controller/dwc/pcie-fu740.c >> index 842b7202b96e..ecac0364178a 100644 >> --- a/drivers/pci/controller/dwc/pcie-fu740.c >> +++ b/drivers/pci/controller/dwc/pcie-fu740.c >> @@ -181,10 +181,60 @@ static int fu740_pcie_start_link(struct dw_pcie >> *pci) >>   { >>       struct device *dev = pci->dev; >>       struct fu740_pcie *afp = dev_get_drvdata(dev); >> +    u8 cap_exp = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP); >> +    int ret; >> +    u32 orig, tmp; >> + >> +    /* >> +     * Force 2.5GT/s when starting the link, due to some devices not >> +     * probing at higher speeds. This happens with the PCIe switch >> +     * on the Unmatched board when U-Boot has not initialised the PCIe. >> +     * The fix in U-Boot is to force 2.5GT/s, which then gets cleared >> +     * by the soft reset does by this driver. >> +     */ >> + >> +    dev_dbg(dev, "cap_exp at %x\n", cap_exp); >> +    dw_pcie_dbi_ro_wr_en(pci); >> + >> +    tmp = dw_pcie_readl_dbi(pci, cap_exp + PCI_EXP_LNKCAP); >> +    orig = tmp & PCI_EXP_LNKCAP_SLS; >> +    tmp &= ~PCI_EXP_LNKCAP_SLS; >> +    tmp |= PCI_EXP_LNKCAP_SLS_2_5GB; >> +    dw_pcie_writel_dbi(pci, cap_exp + PCI_EXP_LNKCAP, tmp); >>         /* Enable LTSSM */ >>       writel_relaxed(0x1, afp->mgmt_base + PCIEX8MGMT_APP_LTSSM_ENABLE); >> -    return 0; >> + >> +    ret = dw_pcie_wait_for_link(pci); >> +    if (ret) { >> +        dev_err(dev, "error: link did not start\n"); >> +        goto err; >> +    } >> + >> +    tmp = dw_pcie_readl_dbi(pci, cap_exp + PCI_EXP_LNKCAP); >> +    if ((tmp & PCI_EXP_LNKCAP_SLS) != orig) { >> +        dev_dbg(dev, "changing speed back to original\n"); >> + >> +        tmp &= ~PCI_EXP_LNKCAP_SLS; >> +        tmp |= orig; >> +        dw_pcie_writel_dbi(pci, cap_exp + PCI_EXP_LNKCAP, tmp); >> + >> +        tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL); >> +        tmp |= PORT_LOGIC_SPEED_CHANGE; >> +        dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp); >> + >> +        ret = dw_pcie_wait_for_link(pci); >> +        if (ret) { >> +            dev_err(dev, "error: link did not start at new speed\n"); >> +            goto err; >> +        } >> +    } >> + >> +    ret = 0; >> +err: >> +    WARN_ON(ret);    /* we assume that errors will be very rare */ >> +    dw_pcie_dbi_ro_wr_dis(pci); >> +    return ret; >>   } >>     static int fu740_pcie_host_init(struct pcie_port *pp) > > +cc Maciej and David as there is this other fix that seems to do the > same but differently, it's been under review for some time now: > https://lore.kernel.org/all/20220302000043.GA662523@bhelgaas/t/ > > I fell onto this issue recently, I'll give your patch and the above a > try soon. FWIW, I have tested this and it solved my issue with nvme not being probed, so: Tested-by: Alexandre Ghiti Thanks, Alex > > Thanks > > Alex > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv