[PATCH v10 4/6] PCI: hisi: Add PCIe host support for HiSilicon SoC Hip05

-----Original Message-----
From: Arnd Bergmann [mailto:arnd at arndb.de]
Sent: Tuesday, October 13, 2015 12:12 PM
To: Bjorn Helgaas
Cc: Wangzhou (B); Bjorn Helgaas; jingoohan1 at gmail.com;
pratyush.anand at gmail.com; linux at arm.linux.org.uk;
thomas.petazzoni at free-electrons.com; Gabriele Paoloni;
lorenzo.pieralisi at arm.com; james.morse at arm.com; Liviu.Dudau at arm.com;
jason at lakedaemon.net; robh at kernel.org; gabriel.fernandez at linaro.org;
Minghuan.Lian at freescale.com; linux-pci at vger.kernel.org; linux-arm-
kernel at lists.infradead.org; devicetree at vger.kernel.org; linux-
kernel at vger.kernel.org; zhangjukuo; qiuzhenfa; liudongdong (C);
qiujiang; xuwei (O); Liguozhu (Kenneth); Wangkefeng (Kevin); Rob
Herring
Subject: Re: [PATCH v10 4/6] PCI: hisi: Add PCIe host support for
HiSilicon SoC Hip05

On Monday 12 October 2015 16:35:45 Bjorn Helgaas wrote:

quoted

quoted

+{
+     u64 addr;
+     struct device_node *msi_node;
+     struct resource res;
+     struct device_node *np = pp->dev->of_node;
+     struct hisi_pcie *pcie = to_hisi_pcie(pp);
+
+     msi_node = of_parse_phandle(np, "msi-parent", 0);
+     if (!msi_node) {
+             dev_err(pp->dev, "failed to find msi-parent\n");
+             return -EINVAL;
+     }
+     of_address_to_resource(msi_node, 0, &res);

Does this use the "msi-parent" node in the same way as other drivers
do?  I'm sure there must be other places where we extract struct
resource information from an "msi-parent" node, but I don't see them.

I'm trying to verify that this isn't some kind of incompatible
extension of the "msi-parent" property.  I cc'd Arnd and Rob (DT
experts).

This is not ok, what this does is that it relies on a particular
implementation of the MSI controller and directly accesses its
registers.

Hi Arnd, thanks for reviewing.

What we do is to retrieve the msi-parent physical address and we store it
in our internal PCIe register locations...

So we do not operate directly on the msi controller registers...

So I wonder if the current implementation is Ok to retrieve the
msi-parent address....

Thanks

Gab

Instead, it should reference only the msi irq domain and let the
driver for the MSI controller access the registers. Otherwise this
code has to be rewritten once the same PCI host code appears in
a machine that has a real GICv2m or GICv3.

	Arnd