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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C1040C4743D for ; Fri, 11 Jun 2021 04:45:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A136361374 for ; Fri, 11 Jun 2021 04:45:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230422AbhFKErr (ORCPT ); Fri, 11 Jun 2021 00:47:47 -0400 Received: from mail-pl1-f181.google.com ([209.85.214.181]:37789 "EHLO mail-pl1-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229562AbhFKErq (ORCPT ); Fri, 11 Jun 2021 00:47:46 -0400 Received: by mail-pl1-f181.google.com with SMTP id h12so2209759plf.4 for ; Thu, 10 Jun 2021 21:45:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=fRxLBozaN4SltyilUViQPuK+PpihOctfxY+FQg2HMuM=; b=Ie7xmferhpcr9Yhmc5415IDEf7zXz7R6ygX4f8Coa/dxeb6OEkqDtCYa1piGT+S4ca rOHGBVQRmKXx9L5V5i7ahqfzUgaJhW0fVzfXkwmJpYmlje7AQrNdhgv4lz+K3n4TA/A+ tvR9qo1GRA2COvzwFlTlfJ8oWavvuW08bUEJLdbY7bLBZkZQVOdKFOPTxtRl+Pwk6j93 LKuruUUTnqhUe6fs2kBlu57LqZwDLtL44mpnMWji4iBnhRmpwN1BXpOoQqlHly4XCtEL wPTVq/g0XSHsLqJQa4m/AXQHYXIOifhLHD1XXNsX2zlgaZMCwQJ/bMEJ4cCWBGBBsYMz t7nA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=fRxLBozaN4SltyilUViQPuK+PpihOctfxY+FQg2HMuM=; b=TpGH+2o/zaO/DVO3ZAWHgwKUfJqf0qtX4/INhzxcvKHIWRRgEGln+uQt9NZtETCCYC uzzxeiLhmkxrjsEcsyZUsh3uDVj1W+leB2Unx6qiFfxuMLuZ9JWUCA6hOCZA24fqaPC0 y/RbVtYxzB5PPgMwXl2JdsMfaOFNAgfn5m+u7QhlWJssdaznOdXfqrX9+yLM4+Bn5COh cuUTPwn4YlyrxrmlJ32ynhCwzqxFmiF8MLEEyKZEuHZmxM1CdE5sp0eeYmQrPhGmrxWV RDI56wnEkwXp451xSEsmeljISZe1sqFxOVNBONYSlNPRC/S6tq6Gh1/c/Z0MjUrRDy2G ORCg== X-Gm-Message-State: AOAM533p2Q68ZM7B5D0aQ3/oa36ln3KwcTFYv2Z3yn4pM4LO7QujXsBl w6CW3SdAK/KwY79lnbEywPEy X-Google-Smtp-Source: ABdhPJyXE5YbnRFjaJKPHPKLkZ0eXnaLHFVXDGyku5AZygmgIdkaC9PWx9cEvRiPPkSF8vurPdsuOA== X-Received: by 2002:a17:90a:a481:: with SMTP id z1mr6987736pjp.165.1623386677654; Thu, 10 Jun 2021 21:44:37 -0700 (PDT) Received: from thinkpad ([2409:4072:6281:d9a2:40f:351d:828b:fc1a]) by smtp.gmail.com with ESMTPSA id h6sm3730181pfk.40.2021.06.10.21.44.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Jun 2021 21:44:37 -0700 (PDT) Date: Fri, 11 Jun 2021 10:14:28 +0530 From: Manivannan Sadhasivam To: Bjorn Andersson Cc: lorenzo.pieralisi@arm.com, robh@kernel.org, bhelgaas@google.com, linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Siddartha Mohanadoss Subject: Re: [PATCH v2 2/3] PCI: dwc: Add Qualcomm PCIe Endpoint controller driver Message-ID: <20210611044428.GA6950@thinkpad> References: <20210603103814.95177-1-manivannan.sadhasivam@linaro.org> <20210603103814.95177-3-manivannan.sadhasivam@linaro.org> <20210609085152.GB15118@thinkpad> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Jun 10, 2021 at 11:28:49PM -0500, Bjorn Andersson wrote: > On Wed 09 Jun 03:51 CDT 2021, Manivannan Sadhasivam wrote: > > On Sat, Jun 05, 2021 at 10:07:15PM -0500, Bjorn Andersson wrote: > > > On Thu 03 Jun 05:38 CDT 2021, Manivannan Sadhasivam wrote: > > > > diff --git a/drivers/pci/controller/dwc/pcie-qcom-ep.c b/drivers/pci/controller/dwc/pcie-qcom-ep.c > [..] > > > > +static irqreturn_t qcom_pcie_ep_perst_threaded_irq(int irq, void *data) > > > > +{ > > > > + struct qcom_pcie_ep *pcie_ep = data; > > > > + struct dw_pcie *pci = &pcie_ep->pci; > > > > + struct device *dev = pci->dev; > > > > + u32 perst; > > > > + > > > > + perst = gpiod_get_value(pcie_ep->reset); > > > > + > > > > + if (perst) { > > > > + /* Start link training */ > > > > + dev_info(dev, "PERST de-asserted by host. Starting link training!\n"); > > > > + qcom_pcie_establish_link(pci); > > > > + } else { > > > > + /* Shutdown the link if the link is already on */ > > > > + dev_info(dev, "PERST asserted by host. Shutting down the PCIe link!\n"); > > > > + qcom_pcie_disable_link(pci); > > > > + } > > > > + > > > > + /* Set trigger type based on the next expected value of perst gpio */ > > > > + irq_set_irq_type(gpiod_to_irq(pcie_ep->reset), > > > > + (perst ? IRQF_TRIGGER_LOW : IRQF_TRIGGER_HIGH)); > > > > > > Looks like you're manually implementing edge triggering, is there any > > > reason for that? EDGE_BOTH seems to do the same thing... > > > > > > > PERST is a level based signal, so I don't think we can use EDGE_BOTH here. > > > > Afaict it's just a gpio and you define if the hardware should fire of > interrupts given its level or if it should detect transitions. > > That said, if the gpio is already high when registering the irq handler > there's no transition. > Right, that's one of the issue with edge triggering. PERST# can be deasserted by the host before EP driver probes. So if we wait for edge transition then we'll be stuck. > > > > + > > > > + return IRQ_HANDLED; > > > > +} > [..] > > > > +static struct platform_driver qcom_pcie_ep_driver = { > > > > + .probe = qcom_pcie_ep_probe, > > > > + .driver = { > > > > + .name = "qcom-pcie-ep", > > > > > > Skip the indentation of the '='. > > > > > > > + .suppress_bind_attrs = true, > > > > > > Why do we suppress_bind_attrs? > > > > > > > This driver doesn't support remove() callback and I don't think it is necessary > > for this platform driver. So this flag is here to prevent unbind from sysfs. > > > > Right, that part makes sense. But do you know why this is, why it's not > possible to have the PCI controller built as a module? (GKI should > want this). > For an endpoint, making this driver built-in makes sense since this forms the basic functionality of the device and we do want it to probe asap (without initramfs dance). But looking at other drivers, most of them (including Qcom RC) doesn't support tristate. But for the GKI requirement, I can add it. Thanks, Mani > Regards, > Bjorn