linux-kernel - Re: [PATCH v2 14/17] PCI: dwc: Check iATU in/outbound ranges setup methods status

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Date:   Mon, 16 May 2022 16:35:06 -0500
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rahul Tanwar <rtanwar@...linear.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 14/17] PCI: dwc: Check iATU in/outbound ranges setup
 methods status

On Wed, May 04, 2022 at 12:46:35AM +0300, Serge Semin wrote:
> Let's make the DWC PCIe RC/EP safer and more verbose for the invalid or
> failed inbound and outbound iATU windows setups. Needless to say that
> silently ignoring iATU regions setup errors may cause unpredictable
> errors. For instance if for some reason a cfg or IO window fails to be
> activated, then any CFG/IO requested won't reach target PCIe devices and
> the corresponding accessors will return platform-specific random values.
> 
> First of all we need to convert dw_pcie_ep_outbound_atu() method to check
> whether the specified outbound iATU range is successfully setup. That
> method is called by the pci_epc_ops.map_addr callback. Thus we'll make the
> EP-specific CPU->PCIe memory mappings saver.
> 
> Secondly since the iATU outbound range programming method now returns the
> operation status, it will be handy to take that status into account in the
> pci_ops.{map_bus,read,write} methods. Thus any failed mapping will be
> immediately noticeable by the PCIe CFG operations requesters.
> 
> Finally we need to convert the dw_pcie_setup_rc() method to returning the
> operation status, since the iATU outbound ranges setup procedure may now
> fail. It will be especially handy in case if the DW PCIe RC DT-node has
> invalid/unsupported (dma-)ranges property. Note since the suggested
> modification causes having too wide code indentation, it is reasonable
> from maintainability and readability points of view to move the outbound
> ranges setup procedure in the separate function.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> ---
>  .../pci/controller/dwc/pcie-designware-ep.c   |   9 +-
>  .../pci/controller/dwc/pcie-designware-host.c | 149 ++++++++++++------
>  drivers/pci/controller/dwc/pcie-designware.h  |   5 +-
>  drivers/pci/controller/dwc/pcie-intel-gw.c    |   6 +-

I worry that this could regress some platforms that happened to work 
before. But only one way to find out...

Reviewed-by: Rob Herring <robh@...nel.org>