linux-kernel - Re: [PATCH v2] PCI: apple: Set only available ports up

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Message-ID: <20230316212217.GI24656@jannau.net>
Date:   Thu, 16 Mar 2023 22:22:17 +0100
From:   Janne Grunau <j@...nau.net>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Marc Zyngier <maz@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Sven Peter <sven@...npeter.dev>, linux-pci@...r.kernel.org,
        asahi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Daire McNamara <daire.mcnamara@...rochip.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v2] PCI: apple: Set only available ports up

On 2023-03-09 10:39:35 -0600, Bjorn Helgaas 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@...000000/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.

Yes, it fixes only the warning and hides devices. The present devices 
still work. I confused myself with the submitted M2 devicetree. It 
missed information in the dt node of an disabled PCIe port breaking 
probing of the pcie controller.
 
I agree that the Cc: stable is not necessary. Please drop it or tell me 
to resend the change.
 
> >   ...
> >   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@...r.kernel.org
> > Reviewed-by: Marc Zyngier <maz@...nel.org>
> > Signed-off-by: Janne Grunau <j@...nau.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.

6fffbc7ae137 avoids the warning and hides the disabled ports as well. I 
think we want to keep this change however in the hope that avoiding the 
port setup of disbled ports saves energy.

Thanks

Janne