Date:   Thu, 16 Mar 2023 11:18:52 +0000
Message-ID: <868rfxx7tv.wl-maz@kernel.org>
From:   Marc Zyngier <maz@kernel.org>
To:     Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc:     Bjorn Helgaas <helgaas@kernel.org>, Janne Grunau <j@jannau.net>,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>,
        Krzysztof =?UTF-8?B?V2lsY3p5xYRza2k=?= <kw@linux.com>,
        Rob Herring <robh@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Sven Peter <sven@svenpeter.dev>, linux-pci@vger.kernel.org,
        asahi@lists.linux.dev, linux-kernel@vger.kernel.org,
        Daire McNamara <daire.mcnamara@microchip.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH v2] PCI: apple: Set only available ports up
In-Reply-To: <ZBLzr1MZ2whtvusL@lpieralisi>
References: <20230307-apple_pcie_disabled_ports-v2-1-c3bd1fd278a4@jannau.net>
        <20230309163935.GA1140101@bhelgaas>
        <86a60dxcr0.wl-maz@kernel.org>
        <ZBLzr1MZ2whtvusL@lpieralisi>
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On Thu, 16 Mar 2023 10:47:11 +0000,
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:
> 
> On Thu, Mar 16, 2023 at 09:32:35AM +0000, Marc Zyngier wrote:
> > On Thu, 09 Mar 2023 16:39:35 +0000,
> > Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > 
> > > [+cc Daire, Conor for apple/microchip use of ECAM .init() method]
> > > 
> > > On Thu, Mar 09, 2023 at 02:36:24PM +0100, Janne Grunau wrote:
> > > > Fixes following warning inside of_irq_parse_raw() called from the common
> > > > PCI device probe path.
> > > > 
> > > >   /soc/pcie@690000000/pci@1,0 interrupt-map failed, using interrupt-controller
> > > >   WARNING: CPU: 4 PID: 252 at drivers/of/irq.c:279 of_irq_parse_raw+0x5fc/0x724
> > > 
> > > Based on this commit log, I assume this patch only fixes the warning,
> > > and the system *works* just fine either way.  If that's the case, it's
> > > debatable whether it meets the stable kernel criteria, although the
> > > documented criteria are much stricter than what happens in practice.
> > > 
> > > >   ...
> > > >   Call trace:
> > > >    of_irq_parse_raw+0x5fc/0x724
> > > >    of_irq_parse_and_map_pci+0x128/0x1d8
> > > >    pci_assign_irq+0xc8/0x140
> > > >    pci_device_probe+0x70/0x188
> > > >    really_probe+0x178/0x418
> > > >    __driver_probe_device+0x120/0x188
> > > >    driver_probe_device+0x48/0x22c
> > > >    __device_attach_driver+0x134/0x1d8
> > > >    bus_for_each_drv+0x8c/0xd8
> > > >    __device_attach+0xdc/0x1d0
> > > >    device_attach+0x20/0x2c
> > > >    pci_bus_add_device+0x5c/0xc0
> > > >    pci_bus_add_devices+0x58/0x88
> > > >    pci_host_probe+0x124/0x178
> > > >    pci_host_common_probe+0x124/0x198 [pci_host_common]
> > > >    apple_pcie_probe+0x108/0x16c [pcie_apple]
> > > >    platform_probe+0xb4/0xdc
> > > > 
> > > > This became apparent after disabling unused PCIe ports in the Apple
> > > > silicon device trees instead of deleting them.
> > > > 
> > > > Use for_each_available_child_of_node instead of for_each_child_of_node
> > > > which takes the "status" property into account.
> > > > 
> > > > Link: https://lore.kernel.org/asahi/20230214-apple_dts_pcie_disable_unused-v1-0-5ea0d3ddcde3@jannau.net/
> > > > Link: https://lore.kernel.org/asahi/1ea2107a-bb86-8c22-0bbc-82c453ab08ce@linaro.org/
> > > > Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
> > > > Cc: stable@vger.kernel.org
> > > > Reviewed-by: Marc Zyngier <maz@kernel.org>
> > > > Signed-off-by: Janne Grunau <j@jannau.net>
> > > > ---
> > > > Changes in v2:
> > > > - rewritten commit message with more details and corrections
> > > > - collected Marc's "Reviewed-by:"
> > > > - Link to v1: https://lore.kernel.org/r/20230307-apple_pcie_disabled_ports-v1-1-b32ef91faf19@jannau.net
> > > > ---
> > > >  drivers/pci/controller/pcie-apple.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> > > > index 66f37e403a09..f8670a032f7a 100644
> > > > --- a/drivers/pci/controller/pcie-apple.c
> > > > +++ b/drivers/pci/controller/pcie-apple.c
> > > > @@ -783,7 +783,7 @@ static int apple_pcie_init(struct pci_config_window *cfg)
> > > >  	cfg->priv = pcie;
> > > >  	INIT_LIST_HEAD(&pcie->ports);
> > > >  
> > > > -	for_each_child_of_node(dev->of_node, of_port) {
> > > > +	for_each_available_child_of_node(dev->of_node, of_port) {
> > > >  		ret = apple_pcie_setup_port(pcie, of_port);
> > > >  		if (ret) {
> > > >  			dev_err(pcie->dev, "Port %pOF setup fail: %d\n", of_port, ret);
> > > 
> > > Is this change still needed after 6fffbc7ae137 ("PCI: Honor firmware's
> > > device disabled status")?  This is a generic problem, and it would be
> > > a lot nicer if we had a generic solution.  But I assume it *is* still
> > > needed because Rob gave his Reviewed-by.
> > 
> > I'm not sure this is addressing the same issue. The way I read it, the
> > patch you mention here allows a PCI device to be disabled in firmware,
> > even if it could otherwise be probed.
> > 
> > What this patch does is to prevent root ports that exist in the HW but
> > that have been disabled from being probed. Same concept, only at a
> > different level.
> 
> A root port is a PCI device though and that's what's causing the warning
> AFAIK (? it is triggered on the root port PCI device pci_assign_irq()
> call),

As usual, there are two sides to things. The root ports are also part
of a platform device, and this what this patch uses.

> I am not sure the root port DT node is associated with the root
> port PCI device correctly, which might explain why, even after
> 6fffbc7ae137, the PCI enumeration code is adding the root port PCI
> device to the PCI tree.

I didn't say that commit did not suppress the warning. I haven't
tested it the first place because I really need all the PCIe ports I
can get on the machines I have.

It just feels to me that they are tracking different things.

> Is the dts available anywhere ? How are root ports described in it ?

arch/arm64/boot/dts/apple/t8103.dtsi
Documentation/devicetree/bindings/pci/apple,pcie.yaml

	M.

-- 
Without deviation from the norm, progress is not possible.