Re: [PATCH 1/2] PCI: rockchip: Work around missing device_type property in DT

From: Bjorn Helgaas <helgaas@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Rob Herring <robh@kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	Roh Herring <robh+dt@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	kernel-team@android.com
Subject: Re: [PATCH 1/2] PCI: rockchip: Work around missing device_type property in DT
Date: Sat, 15 Aug 2020 18:22:28 -0500	[thread overview]
Message-ID: <20200815232228.GA1325245@bjorn-Precision-5520> (raw)
In-Reply-To: <20200815125112.462652-2-maz@kernel.org>

On Sat, Aug 15, 2020 at 01:51:11PM +0100, Marc Zyngier wrote:
> Recent changes to the DT PCI bus parsing made it mandatory for
> device tree nodes describing a PCI controller to have the
> 'device_type = "pci"' property for the node to be matched.
> 
> Although this follows the letter of the specification, it
> breaks existing device-trees that have been working fine
> for years.  Rockchip rk3399-based systems are a prime example
> of such collateral damage, and have stopped discovering their
> PCI bus.
> 
> In order to paper over the blunder, let's add a workaround
> to the pcie-rockchip driver, adding the missing property when
> none is found at boot time. A warning will hopefully nudge the
> user into updating their DT to a fixed version if they can, but
> the insentive is obviously pretty small.

s/insentive/incentive/ (Lorenzo or I can fix this up)

> Fixes: 2f96593ecc37 ("of_address: Add bus type match for pci ranges parser")
> Suggested-by: Roh Herring <robh+dt@kernel.org>

s/Roh/Rob/ (similarly)

> Signed-off-by: Marc Zyngier <maz@kernel.org>

This looks like a candidate for v5.9, since 2f96593ecc37 was merged
during the v5.9 merge window, right?

I wonder how many other DTs are similarly broken?  Maybe Rob's DT
checker has already looked?

> ---
>  drivers/pci/controller/pcie-rockchip-host.c | 29 +++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
> index 0bb2fb3e8a0b..d7dd04430a99 100644
> --- a/drivers/pci/controller/pcie-rockchip-host.c
> +++ b/drivers/pci/controller/pcie-rockchip-host.c
> @@ -949,6 +949,35 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
>  	if (!dev->of_node)
>  		return -ENODEV;
>  
> +	/*
> +	 * Most rk3399 DTs are missing the 'device_type = "pci"' property,
> +	 * potentially leading to PCIe probing failure. Be kind to the
> +	 * users and fix it up for them. Upgrading is recommended.
> +	 */
> +	if (!of_find_property(dev->of_node, "device_type", NULL)) {
> +		const char dtype[] = "pci";
> +		struct property *prop;
> +
> +		dev_warn(dev, "Working around missing device_type property\n");
> +
> +		prop = kzalloc(sizeof(*prop), GFP_KERNEL);
> +		if (!prop)
> +			return -ENOMEM;
> +
> +		prop->name	= kstrdup("device_type", GFP_KERNEL);
> +		prop->value	= kstrdup(dtype, GFP_KERNEL);
> +		prop->length	= ARRAY_SIZE(dtype);
> +		if (!prop->name || !prop->value) {
> +			kfree(prop->name);
> +			kfree(prop->value);
> +			kfree(prop);
> +			return -ENOMEM;
> +		}
> +
> +		if (of_add_property(dev->of_node, prop))
> +			dev_warn(dev, "Failed to add property, probing may fail");
> +	}
> +
>  	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*rockchip));
>  	if (!bridge)
>  		return -ENOMEM;
> -- 
> 2.27.0
> 
> 
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