linux-kernel - Re: [PATCH v9 4/4] PCI: dwc: Support ECAM mechanism by enabling iATU 'CFG Shift Feature'

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Message-ID: <a4c6d47f-28b5-40d3-bc82-10aeb14f8e78@oss.qualcomm.com>
Date: Sat, 29 Nov 2025 07:54:35 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Manivannan Sadhasivam <mani@...nel.org>,
        Jingoo Han
 <jingoohan1@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Alim Akhtar
 <alim.akhtar@...sung.com>,
        Jonathan Chocron <jonnyc@...zon.com>, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v9 4/4] PCI: dwc: Support ECAM mechanism by enabling iATU
 'CFG Shift Feature'



On 11/28/2025 10:46 PM, Maciej W. Rozycki wrote:
> On Fri, 28 Nov 2025, Krishna Chaitanya Chundru wrote:
>
>>>    I have no slightest idea why it should cause a regression such as this,
>>> it seems totally unrelated.  Yet it's 100% reproducible.  Could this be
>>> because it's the only device in the system that actually uses PCI/e port
>>> I/O?
>> Hi Maciej, Can you try attached patch and let me know if that is helping you
>> or not. - Krishna Chaitanya.
>   No change, it's still broken, sorry.
HI Maciej,
For the previous patch can you apply this diff and share me dmesg o/p
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -448,7 +448,6 @@ static int dw_pcie_config_ecam_iatu(struct 
dw_pcie_rp *pp)
         if (ret)
                 return ret;

-
         bus_range_max = resource_size(bus->res);

         if (bus_range_max < 2)
@@ -456,6 +455,8 @@ static int dw_pcie_config_ecam_iatu(struct 
dw_pcie_rp *pp)

         pp->ob_atu_index++;

+       dev_err(pci->dev, "Current iATU OB index %d\n", pp->ob_atu_index);
+
         /* Configure remaining buses in type 1 iATU configuration */
         atu.index = pp->ob_atu_index;
         atu.type = PCIE_ATU_TYPE_CFG1;
@@ -931,6 +932,7 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
                 }
         }

+       dev_err(pci->dev, "Current iATU OB index %d\n", i);
         if (pp->io_size) {
                 if (pci->num_ob_windows > ++i) {
                         atu.index = i;
@@ -946,6 +948,7 @@ static int dw_pcie_iatu_setup(struct dw_pcie_rp *pp)
                                 return ret;
                         }
                 } else {
+                       dev_err(pci->dev, "Using shared io index %d\n", i);
                         pp->cfg0_io_shared = true;
                 }
         }

- Krishna Chaitanya.
>    Maciej