linux-kernel - Re: [PATCH v3] PCI/ACPI: xgene: Add ECAM quirk for X-Gene PCIe controller

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Message-ID: <20161205215318.GB22455@bhelgaas-glaptop.roam.corp.google.com>
Date:   Mon, 5 Dec 2016 15:53:18 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Duc Dang <dhdang@....com>
Cc:     Rafael Wysocki <rafael@...nel.org>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Salter <msalter@...hat.com>, linux-pci@...r.kernel.org,
        linux-arm <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jon Masters <jcm@...hat.com>, Tomasz Nowicki <tn@...ihalf.com>,
        patches <patches@....com>
Subject: Re: [PATCH v3] PCI/ACPI: xgene: Add ECAM quirk for X-Gene PCIe
 controller

On Thu, Dec 01, 2016 at 06:52:23PM -0800, Duc Dang wrote:
> On Thu, Dec 1, 2016 at 10:33 AM, Bjorn Helgaas <helgaas@...nel.org> wrote:

> I made similar changes in v4 patch. The ECAM quirk will be built when
> ACPI and PCI_QUIRKS are enabled.
> 
> When building for DT only, the ECAM quirk won't be compiled.

Perfect.

> >>  #define XGENE_PCIE_IP_VER_UNKN               0
> >>  #define XGENE_PCIE_IP_VER_1          1
> >> +#define XGENE_PCIE_IP_VER_2          2
> >
> > This isn't used anywhere, which makes me wonder whether it's worth
> > keeping it.
> 
> V2 controller will use this XGENE_PCIE_IP_VER_2 (port->version =
> XGENE_PCIE_IP_VER_2). This will be used to indicate that the
> controller is V2, and to enable configuration request retry status
> feature (by not disable it like V1 controller).

OK, I see.  You don't actually need XGENE_PCIE_IP_VER_2, you just need
port->version to be something other than XGENE_PCIE_IP_VER_1.  So this
is fine as it is.

> >>  static void __iomem *xgene_pcie_get_cfg_base(struct pci_bus *bus)
> >>  {
> >> -     struct xgene_pcie_port *port = bus->sysdata;
> >> +     struct pci_config_window *cfg;
> >> +     struct xgene_pcie_port *port;
> >> +
> >> +     if (acpi_disabled)
> >> +             port = bus->sysdata;
> >> +     else {
> >> +             cfg = bus->sysdata;
> >> +             port = cfg->priv;
> >> +     }
> >
> > I would really, really like to figure out a way to get rid of these
> > "if (acpi_disabled)" checks sprinkled through here.  Is there any way
> > we can set up bus->sysdata to be the same, regardless of whether we're
> > using this as a platform driver or an ACPI quirk?
> 
> Right now, I created a inline function to extract xgene_pcie_port from
> pci_bus. In order to get rid of acpi_disabled, I will need to make
> sysdata in DT case also point to pci_config_window structure, which
> means I will need to convert and test the DT driver to use ecam ops.
> It is a separate patch itself. So I think I should do it at later time
> (after this ECAM quirk patch). I hope you are ok with this.

OK.  I did the simple-minded version of leaving the DT ops the same
but making sysdata point to a dummy pci_config_window.  Your proposal
of using ECAM for DT would be much better.

It's interesting that you actually already use the same accessors
except that DT uses the 32-bit pci_generic_config_write32() and ACPI
uses the regular pci_generic_config_write(). I guess that means the
hardware actually *does* support sub-32 bit writes?

> I need to define the function (xgene_get_csr_resource()) inside
> pci-xgene.c to duplicate the code of acpi_get_rc_addr. The reason is
> X-Gene firmware does not have a dedicate PNP0C02 node to declare the
> resource, and if I use acpi_get_rc_resources() with "PNP0A08", I got
> error due to acpi_bus_get_device() returns error.

Looks good.

> > All these init functions are almost identical.  Can we factor this out
> > by having wrappers that do nothing more than pass in the table and
> > version, and put the kzalloc and ioremap in a shared back-end?
> 
> I refactor-ed these .init functions. And as a result, there are only 2
> ecam ops left: xgene_v1_pcie_ecam_ops and xgene_v2_pcie_ecam_ops.

Looks good.

Bjorn