linux-kernel - Re: [PATCH v2 1/3] PCI: endpoint: Handle 64-bit BARs properly

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Message-ID: <20180213102853.GA8981@e107981-ln.cambridge.arm.com>
Date:   Tue, 13 Feb 2018 10:28:53 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Niklas Cassel <niklas.cassel@...s.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Sekhar Nori <nsekhar@...com>,
        Cyrille Pitchen <cyrille.pitchen@...e-electrons.com>,
        Niklas Cassel <niklass@...s.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        John Keeping <john@...anate.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] PCI: endpoint: Handle 64-bit BARs properly

On Fri, Feb 09, 2018 at 06:14:49PM +0530, Kishon Vijay Abraham I wrote:
> Hi Bjorn,
> 
> On Friday 09 February 2018 03:27 AM, Bjorn Helgaas wrote:
> > On Thu, Feb 08, 2018 at 06:17:32PM +0530, Kishon Vijay Abraham I wrote:
> >> Hi,
> >>
> >> On Thursday 08 February 2018 06:03 PM, Niklas Cassel wrote:
> >>> A 64-bit BAR uses the succeeding BAR for the upper bits, therefore
> >>> we cannot call pci_epc_set_bar() on a BAR that follows a 64-bit BAR.
> >>>
> >>> If pci_epc_set_bar() is called with flag PCI_BASE_ADDRESS_MEM_TYPE_64,
> >>
> >> Not related to $patch. But I have a query on when
> >> PCI_BASE_ADDRESS_MEM_TYPE_64 should be set. Whether if the size is >
> >> 4G or if the address can be mapped anywhere in the 64-bit PCIe
> >> address space or both?
> > 
> > In general, PCI_BASE_ADDRESS_MEM_TYPE_64 should be set if the BAR is
> > 64 bits wide.  IORESOURCE_MEM_64 is similar.
> 
> okay, if the HW support 64bit BAR, 64 bit flag should be set and not based on
> size or anything else?

Yes, I completely agree with Bjorn. Actually it would be a good idea to
make the struct pci_epf->bar member array an array of struct resources
to simplify its handling.

Thanks,
Lorenzo