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

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Date:   Thu, 9 Mar 2023 10:39:35 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Janne Grunau <j@...nau.net>
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

[+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.

>   ...
>   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.

Not related to this patch, but this function looks funny to me.  Most
pci_ecam_ops.init functions just set up ECAM-related things.

In addition to ECAM stuff, apple_pcie_init() and mc_platform_init()
also initialize IRQs, clocks, and resets.

Maybe we shoehorn the IRQ, clock, reset setup into pci_ecam_ops.init
because we lack a generic hook for doing those things, but it seems a
little muddy conceptually.

Bjorn