linux-kernel - Re: [PATCH 4/5] PCI: aardvark: Implement driver 'remove' function and allow to build it as module

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Date:   Tue, 4 Aug 2020 09:24:32 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Marek Behún <marek.behun@....cz>,
        PCI <linux-pci@...r.kernel.org>,
        Tomasz Maciej Nowak <tmn505@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>, Xogium <contact@...ium.me>
Subject: Re: [PATCH 4/5] PCI: aardvark: Implement driver 'remove' function
 and allow to build it as module

On Monday 03 August 2020 14:00:37 Rob Herring wrote:
> On Mon, Aug 3, 2020 at 8:46 AM Pali Rohár <pali@...nel.org> wrote:
> >
> > On Wednesday 29 July 2020 12:48:09 Rob Herring wrote:
> > > On Wed, Jul 15, 2020 at 04:25:56PM +0200, Marek Behún wrote:
> > > > From: Pali Rohár <pali@...nel.org>
> > > >
> > > > Providing driver's 'remove' function allows kernel to bind and unbind devices
> > > > from aardvark driver. It also allows to build aardvark driver as a module.
> > > >
> > > > Compiling aardvark as a module simplifies development and debugging of
> > > > this driver as it can be reloaded at runtime without the need to reboot
> > > > to new kernel.
> > > >
> > > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > > Reviewed-by: Marek Behún <marek.behun@....cz>
> > > > ---
> > > >  drivers/pci/controller/Kconfig        |  2 +-
> > > >  drivers/pci/controller/pci-aardvark.c | 25 ++++++++++++++++++++++---
> > > >  2 files changed, 23 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/pci/controller/Kconfig b/drivers/pci/controller/Kconfig
> > > > index adddf21fa381..f9da5ff2c517 100644
> > > > --- a/drivers/pci/controller/Kconfig
> > > > +++ b/drivers/pci/controller/Kconfig
> > > > @@ -12,7 +12,7 @@ config PCI_MVEBU
> > > >     select PCI_BRIDGE_EMUL
> > > >
> > > >  config PCI_AARDVARK
> > > > -   bool "Aardvark PCIe controller"
> > > > +   tristate "Aardvark PCIe controller"
> > > >     depends on (ARCH_MVEBU && ARM64) || COMPILE_TEST
> > > >     depends on OF
> > > >     depends on PCI_MSI_IRQ_DOMAIN
> > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > > > index d5f58684d962..0a5aa6d77f5d 100644
> > > > --- a/drivers/pci/controller/pci-aardvark.c
> > > > +++ b/drivers/pci/controller/pci-aardvark.c
> > > > @@ -14,6 +14,7 @@
> > > >  #include <linux/irq.h>
> > > >  #include <linux/irqdomain.h>
> > > >  #include <linux/kernel.h>
> > > > +#include <linux/module.h>
> > > >  #include <linux/pci.h>
> > > >  #include <linux/init.h>
> > > >  #include <linux/phy/phy.h>
> > > > @@ -1114,6 +1115,7 @@ static int advk_pcie_probe(struct platform_device *pdev)
> > > >
> > > >     pcie = pci_host_bridge_priv(bridge);
> > > >     pcie->pdev = pdev;
> > > > +   platform_set_drvdata(pdev, pcie);
> > > >
> > > >     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > >     pcie->base = devm_ioremap_resource(dev, res);
> > > > @@ -1204,18 +1206,35 @@ static int advk_pcie_probe(struct platform_device *pdev)
> > > >     return 0;
> > > >  }
> > > >
> > > > +static int advk_pcie_remove(struct platform_device *pdev)
> > > > +{
> > > > +   struct advk_pcie *pcie = platform_get_drvdata(pdev);
> > > > +   struct pci_host_bridge *bridge = pci_host_bridge_from_priv(pcie);
> > > > +
> > > > +   pci_stop_root_bus(bridge->bus);
> > > > +   pci_remove_root_bus(bridge->bus);
> > >
> > > Based on pci_host_common_remove() implementation, doesn't this need a
> > > lock around it (pci_lock_rescan_remove)?
> >
> > Well, I'm not sure. I looked into other pci drivers and none of
> > following drivers pci-tegra.c, pcie-altera.c, pcie-brcmstb.c,
> > pcie-iproc.c, pcie-mediatek.c, pcie-rockchip-host.c calls
> > pci_lock_rescan_remove() and pci_unlock_rescan_remove().
> 
> The mutex protects the bus->devices list, so yes I believe it is needed.
> 
> Rob

Thank you Rob! It means that all above pci drivers should be fixed too.

I will prepare a new version of aardvark patches with protecting pci
stop/remove functions. And later I can look at some common bridge remove
function for fixing those other pci drivers.