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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 961B6CD3423 for ; Mon, 4 May 2026 06:24:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=eoDyIB9MKLnXGCh0r+3x/f8pDxF2OmHPG/aL1VQ2lUw=; b=nTenWTrvRq9jqgF/BzJ3mn20p4 4iTnmZMbOPoV0EVQFzI7d+a4BlGhScMOVACiWl7Iyl/pOFkBHzW6/8M/q3cEn03kYTQzECohufQAb 2Z4t8lgpd3NgFJuKHLlH9LcRvsNU98OFt6lJ7AI6q87q+264Kcmn0+1tNZ7/EOT+knHSvia5xubNw jdXD0BVvdOIvMm5ghNaBDTXkOBjUcWdul37d6RBKZNsaf3MvBHjXvtAhAvJL3t7toRyMQZupeWpGx MIn7CWQ8aJr3s9EvY5Vx7uE/z9chYhVQH9+mrzJMnJ/dj2NFEgB2owPvVnua9nOuUG2b/owBN5hzM +tL7q51A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJmiz-0000000CUoo-0KeL; Mon, 04 May 2026 06:24:13 +0000 Received: from m16.mail.163.com ([220.197.31.4]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJmiv-0000000CUl2-3zeb for linux-arm-kernel@lists.infradead.org; Mon, 04 May 2026 06:24:11 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=Message-ID:Date:MIME-Version:Subject:To:From: Content-Type; bh=eoDyIB9MKLnXGCh0r+3x/f8pDxF2OmHPG/aL1VQ2lUw=; b=MW0kuarWRqO895SdwzFvchUvvnwO4oPHaj9gpWOd7wlRac/b7eGBP4oVPstXsD +pMzLTGe+Q/O+Rth1SCCBAInEiTi0FDzvGQjFAGEc27WNasCYwxacLaQKsLhrhYm O1wPY0uYzCS6NiggMqlVbjzQQ2jEVi5EOaldtNOsGbCUw= Received: from [192.168.50.71] (unknown []) by gzsmtp3 (Coremail) with SMTP id PigvCgAX2IFmO_hpvbviCA--.227S2; Mon, 04 May 2026 14:23:38 +0800 (CST) Message-ID: Date: Mon, 4 May 2026 14:23:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] PCI: cadence: Ensure that cdns_pcie_host_wait_for_link() waits 100 ms after link up To: Siddharth Vadapalli Cc: bhelgaas@google.com, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, vigneshr@ti.com, robh@kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260501153553.66382-1-18255117159@163.com> <20260501153553.66382-2-18255117159@163.com> <4ce9f13a-b17f-4149-ade8-57519f4a4752@ti.com> <699bd359-7389-45fa-a79b-10046f73bf12@163.com> Content-Language: en-US From: Hans Zhang <18255117159@163.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: PigvCgAX2IFmO_hpvbviCA--.227S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3XFyrGr1DZry3WFyUJFy7Jrb_yoWxAFy7pa yUWF1xKF40qr45u3Wvv3WUZrySqr98GFy7Gw4kKa4xZrnrCr17tF42gF43WF9xGrs0vr17 Z3WUtF9rGF1YvFJanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07U5DGOUUUUU= X-Originating-IP: [140.206.53.66] X-CM-SenderInfo: rpryjkyvrrlimvzbiqqrwthudrp/xtbC7AqBJWn4O2qsAwAA3t X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260503_232410_517695_A4FD7F94 X-CRM114-Status: GOOD ( 28.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/4/26 13:08, Siddharth Vadapalli wrote: > On 03/05/26 21:16, Hans Zhang wrote: >> >> >> On 5/2/26 13:18, Siddharth Vadapalli wrote: >>> On 01/05/26 21:05, Hans Zhang wrote: >>>> As per PCIe r6.0, sec 6.6.1, a Downstream Port that supports Link >>>> speeds >>>> greater than 5.0 GT/s, software must wait a minimum of 100 ms after >>>> Link >>>> training completes before sending a Configuration Request. >>>> >>>> Add a new 'max_link_speed' field in struct cdns_pcie to record the >>>> maximum supported (or currently configured) link speed of the >>>> controller. >>>> >>>> In cdns_pcie_host_wait_for_link(), after the link is reported as up, >>>> insert a 100 ms delay if max_link_speed > 2 (i.e., > 5 GT/s). This >>>> implements the required delay at the common Cadence host layer. >>>> >>>> Currently max_link_speed is zero-initialized, so the delay is not yet >>>> active. Glue drivers must set max_link_speed appropriately to enable >>>> the delay. This matches the approach taken for the Synopsys DWC >>>> controller in commit 80dc18a0cba8d ("PCI: dwc: Ensure that >>>> dw_pcie_wait_for_link() waits 100 ms after link up"). >>>> >>>> Signed-off-by: Hans Zhang <18255117159@163.com> >>>> --- >>>>   .../pci/controller/cadence/pcie-cadence-host-common.c    | 9 +++++ >>>> ++++ >>>>   drivers/pci/controller/cadence/pcie-cadence.h            | 2 ++ >>>>   2 files changed, 11 insertions(+) >>>> >>>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host- >>>> common.c b/drivers/pci/controller/cadence/pcie-cadence-host-common.c >>>> index 2b0211870f02..d4ae762f423f 100644 >>>> --- a/drivers/pci/controller/cadence/pcie-cadence-host-common.c >>>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host-common.c >>>> @@ -14,6 +14,7 @@ >>>>   #include "pcie-cadence.h" >>>>   #include "pcie-cadence-host-common.h" >>>> +#include "../../pci.h" >>>>   #define LINK_RETRAIN_TIMEOUT HZ >>>> @@ -55,6 +56,14 @@ int cdns_pcie_host_wait_for_link(struct cdns_pcie >>>> *pcie, >>>>       /* Check if the link is up or not */ >>>>       for (retries = 0; retries < LINK_WAIT_MAX_RETRIES; retries++) { >>>>           if (pcie_link_up(pcie)) { >>>> +            /* >>>> +             * As per PCIe r6.0, sec 6.6.1, a Downstream Port that >>>> +             * supports Link speeds greater than 5.0 GT/s, software >>>> +             * must wait a minimum of 100 ms after Link training >>>> +             * completes before sending a Configuration Request. >>>> +             */ >>>> +            if (pcie->max_link_speed > 2) >>>> +                msleep(PCIE_RESET_CONFIG_WAIT_MS); >>> >>> I think the above could be moved to cdns_pcie_host_start_link() as >>> follows: >>> >>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host- >>> common.c b/ drivers/pci/controller/cadence/pcie-cadence-host-common.c >>> index 2b0211870f02..0f885dcbdb12 100644 >>> --- a/drivers/pci/controller/cadence/pcie-cadence-host-common.c >>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host-common.c >>> @@ -115,6 +115,15 @@ int cdns_pcie_host_start_link(struct >>> cdns_pcie_rc *rc, >>>       if (!ret && rc->quirk_retrain_flag) >>>           ret = cdns_pcie_retrain(pcie, pcie_link_up); >>> >>> +    /* >>> +     * As per PCIe r6.0, sec 6.6.1, a Downstream Port that >>> +     * supports Link speeds greater than 5.0 GT/s, software >>> +     * must wait a minimum of 100 ms after Link training >>> +     * completes before sending a Configuration Request. >>> +     */ >>> +    if (!ret && pcie->max_link_speed > 2) >>> +        msleep(PCIE_RESET_CONFIG_WAIT_MS); >>> + >>>       return ret; >>>   } >>>   EXPORT_SYMBOL_GPL(cdns_pcie_host_start_link); >>> >>> This will avoid an additional and unnecessary delay when >>> 'cdns_pcie_retrain()' retrains the link. >>> >>> Instead of checking for the link being up using "pcie_link_up(pcie)", >>> checking for 'ret' being zero should also work (ret being zero >>> indicates that the link is up). >>> >>> Since configuration space accesses will not be performed until >>> cdns_pcie_host_start_link() completes executing, it should be safe to >>> switch to the above implementation. >> >> Hi Siddharth, >> >> I think this is applicable to LGA IP as per the method you mentioned. >> However, for HPA IP, additional repetitive code needs to be added in >> the following code. > > Yes, additional code is required as you rightly pointed out, but the > problem I was trying to address with your patch is the following: >     cdns_pcie_host_start_link() >       calls cdns_pcie_host_wait_for_link() >         Link is Up and we wait for 100 ms here >       calls cdns_pcie_retrain() >           calls cdns_pcie_host_wait_for_link() a second time >             Link is Up again after retraining and we wait and >             we wait an additional 100 ms here. > > Instead, it will be sufficient if we could wait just once after > cdns_pcie_retrain() returns. Hi Siddharth, Yes, I looked at the code and indeed it works this way. Because of the abundance of redundant comments. I'm wondering if it's possible to encapsulate a helper function in the file drivers/pci/controller/pci-host-common.c, so that controller drivers like dwc and cadence can call this API. Or do you know where it would be appropriate to place it? Hello, Bjorn and Mani, I wonder what your opinions are. > >> >> Regarding the "quirk_retrain_flag" tag, I reviewed this submission >> record and it appears to be a workaround method. Can it be considered >> that it is not a universal method? Or is the same processing logic >> also added in the HPA? > > I am not sure, but to the best of my knowledge, the quirk is not > applicable to HPA. > The SOC of our company is HPA IP, and it doesn't require this flag setting. Best regards, Hans >> >> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c b/ >> drivers/pci/controller/cadence/pcie-cadence-host-hpa.c >> index 0f540bed58e8..65159f52067d 100644 >> --- a/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c >> +++ b/drivers/pci/controller/cadence/pcie-cadence-host-hpa.c >> @@ -305,6 +305,15 @@ int cdns_pcie_hpa_host_link_setup(struct >> cdns_pcie_rc *rc) >>          if (ret) >>                  dev_dbg(dev, "PCIe link never came up\n"); >> >> +       /* >> +        * As per PCIe r6.0, sec 6.6.1, a Downstream Port that >> +        * supports Link speeds greater than 5.0 GT/s, software >> +        * must wait a minimum of 100 ms after Link training >> +        * completes before sending a Configuration Request. >> +        */ >> +       if (pcie->max_link_speed > 2) >> +               msleep(PCIE_RESET_CONFIG_WAIT_MS); >> + >>          return ret; >>   } >>   EXPORT_SYMBOL_GPL(cdns_pcie_hpa_host_link_setup); >> >> Best regards, >> Hans > > [TRIMMED] > > Regards, > Siddharth.