[PATCH v2] PCI: layerscape: Add PCIe support for LS1043a and LS2080a

[Minghuan.Lian@freescale.com (Lian M.H.)]

Hi Duc,

I notice your patches removed all the related MSI code and you descriptor said " Remove this unnecessary code. This also avoids a warning message ("failed to enable MSI") during boot ".  
I have a question.
Do we need a warning when MSI-parent is missing?

Thanks,
Minghuan

> -----Original Message-----
> From: Duc Dang [mailto:dhdang at apm.com]
> Sent: Monday, October 12, 2015 9:48 AM
> To: Bjorn Helgaas <helgaas@kernel.org>
> Cc: Lian Minghuan-B31939 <Minghuan.Lian@freescale.com>;
> linux-pci at vger.kernel.org; linux-arm <linux-arm-kernel@lists.infradead.org>;
> Zang Roy-R61911 <tie-fei.zang@freescale.com>; Hu Mingkai-B21284
> <Mingkai.Hu@freescale.com>; Yoder Stuart-B08248
> <stuart.yoder@freescale.com>; Li Yang-Leo-R58472 <LeoLi@freescale.com>;
> Arnd Bergmann <arnd@arndb.de>; Bjorn Helgaas <bhelgaas@google.com>;
> Jingoo Han <jg1.han@samsung.com>; Zhou Wang
> <wangzhou1@hisilicon.com>; Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com>; Jason Cooper
> <jason@lakedaemon.net>; Tanmay Inamdar <tinamdar@apm.com>
> Subject: Re: [PATCH v2] PCI: layerscape: Add PCIe support for LS1043a and
> LS2080a
> 
> On Sun, Oct 11, 2015 at 12:10 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> > [+cc Thomas, Jason, Tanmay]
> >
> > Hi Minghuan,
> >
> > You responded to this message, but your response was rejected by the
> > mailing list, I think because it was not plain text.  See
> > http://vger.kernel.org/majordomo-info.html
> >
> > I went ahead and reconstructed what your response would have looked
> > like so I could continue the conversation.  But please fix your email
> > setup before responding again :)
> >
> > Minghuan wrote:
> >> On Wed, Oct 07, 2015 at 12:57:25PM -0500, Bjorn Helgaas wrote:
> >> > Hi Minghuan,
> >> >
> >> > On Thu, Sep 17, 2015 at 05:13:39PM +0800, Minghuan Lian wrote:
> >> > > The patch adds PCIe support for LS1043a and LS2080a.
> >> > >
> >> > > Signed-off-by: Minghuan Lian <Minghuan.Lian@freescale.com>
> >> > > ---
> >> > > This patch is based on v4.3-rc1 and [PATCH v9 0/6]
> >> > > PCI: hisi: Add PCIe host support for HiSilicon SoC Hip05 patchset
> >> > > from Zhou Wang.
> >> > >
> >> > > change log
> >> > > v2:
> >> > > 1. rename ls2085a to ls2080a
> >> > > 2. Add ls_pcie_msi_host_init()
> >> > >
> >> > >  drivers/pci/host/Kconfig          |   2 +-
> >> > >  drivers/pci/host/pci-layerscape.c | 227
> >> > > ++++++++++++++++++++++++++------------
> >> > >  2 files changed, 157 insertions(+), 72 deletions(-)
> >> > >
> >> > > diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> >> > > index ae873be..38fe8a8 100644
> >> > > --- a/drivers/pci/host/Kconfig
> >> > > +++ b/drivers/pci/host/Kconfig
> >> > > @@ -105,7 +105,7 @@ config PCI_XGENE_MSI
> >> > >
> >> > >  config PCI_LAYERSCAPE
> >> > >   bool "Freescale Layerscape PCIe controller"
> >> > > - depends on OF && ARM
> >> > > + depends on OF && (ARM || ARM64)
> >> >
> >> > It seems like there are a couple things going on here, and I wonder
> >> > if you can split them out into separate patches.
> >> >
> >> > 1) Making this work on ARM64 as well as on ARM.  This may be of
> >> > interest for other DesignWare-based drivers, so if you split this
> >> > out, maybe it would be a useful template for converting the other
> >> > drivers, too.
> >> >
> >> > 2) Adding LS1043a and LS2080a.  Obviously, this is only of interest
> >> > to this driver, but maybe it could be separated out into a separate
> >> > patch?
> >
> >> The patch is based on v4.3-rc1 and [PATCH v9 0/6] PCI: hisi: Add PCIe
> >> host support for HiSilicon SoC Hip05 patchset from Zhou Wang which
> >> adds arm and
> >> arm64 support.
> >>
> >> The original code with the Zhou Wang's patches can support arm64 as well.
> >> Because both LS1043a and LS2085 are armv8 (arm64) architecture, the
> >> patch updates Kconfig to add 'arm64'.
> >>
> >> If splitting two patches, the first patch for arm64 support only
> >> includes one line changes of Kconfig. So, I think it is unnecessary.
> >
> > It's OK if the first patch is very small.  The point is that the patch
> > does two orthogonal things, and those two things should be in separate
> > commits.  This makes bisection work better, and it reduces the amount
> > of functionality removed if we have to revert something.
> >
> >> > > +static int ls_pcie_msi_host_init(struct pcie_port *pp,
> >> > > +                          struct msi_controller *chip) {  struct
> >> > > +device_node *msi_node;  struct device_node *np =
> >> > > +pp->dev->of_node;
> >> > > +
> >> > > + msi_node = of_parse_phandle(np, "msi-parent", 0); if
> >> > > + (!msi_node) {
> >> > > +         dev_err(pp->dev, "failed to find msi-parent\n");
> >> > > +         return -EINVAL;
> >> > > + }
> >> >
> >> > This doesn't actually *do* anything except complain if "msi-parent"
> >> > is missing.  I'm not sure that's worth doing: if we need "msi-parent"
> >> > somewhere, we should complain there if we don't find it.  If we
> >> > don't need it, why complain if it's missing?
> >
> >> driver/of/irq.c  void of_msi_configure(struct device *dev, struct
> >> device_node *np) will bind "msi-parent" to each device if there is
> >> "msi-parent" handler. The PCIe driver do not need to do anything. If
> >> we do not check "msi-parent" here, we will have no chance to check it.
> >> The common code of 'of' and 'pci' bus driver will not complain,
> >> because the msi controller may be found by other way.
> >
> > Hmm.   In mvebu_pcie_msi_enable() and xgene_pcie_msi_enable(), we
> > also look for "msi-parent".  If that fails, mvebu continues silently
> > and xgene complains (but only if CONFIG_PCI_MSI=y).
> >
> > This seems like three unnecessarily different ways of doing the same
> > thing.
> 
> For X-Gene MSI, this is the old code where at the time the code was prepared,
> msi_controller needs to be assigned to a host bridge so that the bridge can
> support MSI. Until now, with recent changes on MSI irqdomain from Marc and
> others, we can drop this msi_controller assignment completely as my recent
> patch that you merged to pci/host-xgene branch:
> https://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/commit/?h=pci/host
> -xgene
> 
> >
> > I cc'd the maintainers of those drivers; maybe we can agree on a
> > single strategy.
> >
> >> > >  static int __init ls_pcie_probe(struct platform_device *pdev)  {
> >> > > ...
> >> > > - ret = ls_add_pcie_port(pcie);
> >> > > - if (ret < 0)
> >> > > + ret = dw_pcie_host_init(pp);
> >> >
> >> > We have several DesignWare-based drivers (dra7xx, exynos, imx6, ks,
> >> > ls, spear13xx), and I'd like to keep their structure as similar as
> >> > possible.  For example, they all have basically this structure:
> >> >
> >> >   X_pcie_probe
> >> >     X_add_pcie_port
> >> >       dw_pcie_host_init             # pp->ops->host_init callback
> >> >         X_pcie_host_init
> >> >           X_pcie_establish_link
> >> >
> >> > This patch removes ls_add_pcie_port() and ls_pcie_establish_link(),
> >> > so we're diverging a bit.  That makes it harder to see the
> >> > similarities across these drivers, which I think is a loss.
> >
> >> I will add X_add_pcie_port. But we do not need X_pcie_establish_link
> >> because we do not need change/reset phy to establish link, besides,
> >> the PCIe controller slot may be not inserted any PCIe device at all.
> >> If each controller waits some time for link, the start time will
> >> increase a lot. In some scenes, long start-up time is not acceptable.
> >
> > If we wait for a timeout trying to establish a link when the slot is
> > empty, it sounds like something's wrong.  Can't we tell from presence
> > detect whether a card is present, even without trying to bring up the
> > link?
> >
> > If we truly do not need a piece like X_pcie_establish_link(), I'm OK
> > with entirely omitting it.  What I really object to is when we have
> > the same functionality two places with different names or structured
> > two different ways.
> >
> > Bjorn
> > --
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> 
> Regards,
> Duc Dang.