linux-kernel - Re: [PATCH] PCI: xilinx: Remove platform/architecture restrictions

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Message-ID: <20170731233608.GA27307@bhelgaas-glaptop.roam.corp.google.com>
Date:   Mon, 31 Jul 2017 18:36:08 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Paul Burton <paul.burton@...tec.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michal Simek <michal.simek@...inx.com>,
        Sören Brinkmann <soren.brinkmann@...inx.com>,
        James Hogan <james.hogan@...tec.com>
Subject: Re: [PATCH] PCI: xilinx: Remove platform/architecture restrictions

On Mon, Jul 31, 2017 at 04:19:13PM -0700, Paul Burton wrote:
> Hi Bjorn,
> 
> On Monday, 31 July 2017 15:58:22 PDT Bjorn Helgaas wrote:
> > On Mon, Jul 24, 2017 at 11:49:22AM +0100, Paul Burton wrote:
> > > Hi Guenter & all,
> > > 
> > > On Monday, 24 July 2017 01:39:37 BST Guenter Roeck wrote:
> > > > The MIPS Boston board configuration tries to enable CONFIG_PCIE_XILINX.
> > > > That doesn't work since PCIE_XILINX depends on ARCH_ZYNQ || MICROBLAZE.
> > > > Remove that restriction.
> > > 
> > > I'd prefer that this patch does not go in standalone. The intent for the
> > > MIPS Boston board is that this driver is enabled for MIPS by this patch:
> > > 
> > > https://patchwork.kernel.org/patch/9794361/
> > > 
> > > But not until after earlier patches in that series fix issues with the
> > > driver:
> > > 
> > > https://patchwork.kernel.org/patch/9794355/
> > > https://patchwork.kernel.org/patch/9794357/
> > > https://patchwork.kernel.org/patch/9794359/
> > > 
> > > That has been held up by disagreement about whether the driver should be
> > > using 0-3 or 1-4 for hardware IRQ numbers, sadly, despite the driver
> > > already being in tree & clearly broken, and my series not changing which
> > > the driver uses...
> >
> > It's true that your v5 series only changes xilinx from using hwirq 0-3
> > to 0-4 (with 0 being unused in both cases, and the addition of 4
> > fixing the "INTD doesn't work" bug).
> 
> That isn't true - the xilinx-pcie driver already uses 1-4, and my change 
> simply prevents it from hitting a WARN() in the IRQ code when doing so.

My apologies.  I was relying on the changelog, which says the current
code "creates an IRQ domain of size 4 (ie.  IRQ numbers 0 through 3)"
and the patch:

  -       port->leg_domain = irq_domain_add_linear(pcie_intc_node, 4,
  +       port->leg_domain = irq_domain_add_linear(pcie_intc_node, 1 + 4,

I'm not enough of an IRQ expert to understand why what I said was
incorrect (other than maybe INTD actually works, but emits a warning?)

> > However, I *would* like to see this issue cleaned up consistently
> > across all our drivers.  I mooted a couple ideas in [1], but nobody
> > seemed interested.  If I merged your series as-is, there would be even
> > less interest.
> 
> I've been travelling & haven't had time to look at any reworks as of yet, but 
> I do think the driver as-is is clearly broken & my fix is a pretty obvious 
> one, even if you would like the driver(s) to improve further in future.

My problem is that if all the drivers work because they use 5 numbers
(0-4), the issue will completely drop off everybody's radar.

> > [1]
> > http://lkml.kernel.org/r/20170712221455.GJ14614@bhelgaas-glaptop.roam.corp.
> > google.com
> > > In any case, I don't really mind if people would rather remove the
> > > architecture restrictions than just add MIPS, but I'd prefer this doesn't
> > > go in until the rest of my series since without at least patch 1 of my
> > > seres this will lead to various WARN()s on Boston boards.
> > > 
> > > Thanks,
> > > 
> > >     Paul
> > > > 
> > > > Cc: Paul Burton <paul.burton@...tec.com>
> > > > Cc: James Hogan <james.hogan@...tec.com>
> > > > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > > > ---
> > > > 
> > > >  drivers/pci/host/Kconfig | 1 -
> > > >  1 file changed, 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> > > > index 89d61c2cbfaa..ed905a5401c3 100644
> > > > --- a/drivers/pci/host/Kconfig
> > > > +++ b/drivers/pci/host/Kconfig
> > > > @@ -71,7 +71,6 @@ config PCI_HOST_GENERIC
> > > > 
> > > >  config PCIE_XILINX
> > > >  
> > > >  	bool "Xilinx AXI PCIe host bridge support"
> > > > 
> > > > -	depends on ARCH_ZYNQ || MICROBLAZE
> > > > 
> > > >  	help
> > > >  	
> > > >  	  Say 'Y' here if you want kernel to support the Xilinx AXI PCIe
> > > >  	  Host Bridge driver.
>