linux-kernel - Re: [PATCH v3 1/5] of/irq: Add msi-parent check to of_msi

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Message-ID: <20251021115517.GA3713879-robh@kernel.org>
Date: Tue, 21 Oct 2025 06:55:17 -0500
From: Rob Herring <robh@...nel.org>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	Sascha Bischoff <sascha.bischoff@....com>,
	Marc Zyngier <maz@...nel.org>,
	Scott Branden <sbranden@...adcom.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Ray Jui <rjui@...adcom.com>,
	Frank Li <Frank.Li@....com>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>
Subject: Re: [PATCH v3 1/5] of/irq: Add msi-parent check to of_msi_xlate()

On Fri, Oct 17, 2025 at 10:47:48AM +0200, Lorenzo Pieralisi wrote:
> In some legacy platforms the MSI controller for a PCI host bridge is
> identified by an msi-parent property whose phandle points at an MSI
> controller node with no #msi-cells property, that implicitly
> means #msi-cells == 0.
> 
> For such platforms, mapping a device ID and retrieving the MSI controller
> node becomes simply a matter of checking whether in the device hierarchy
> there is an msi-parent property pointing at an MSI controller node with
> such characteristics.
> 
> Add a helper function to of_msi_xlate() to check the msi-parent property in
> addition to msi-map and retrieve the MSI controller node (with a 1:1 ID
> deviceID-IN<->deviceID-OUT  mapping) to provide support for deviceID
> mapping and MSI controller node retrieval for such platforms.
> 
> Fixes: 57d72196dfc8 ("irqchip/gic-v5: Add GICv5 ITS support")
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Cc: Sascha Bischoff <sascha.bischoff@....com>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/of/irq.c | 38 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 35 insertions(+), 3 deletions(-)

It all looks good to me other than 1 nit below. How do you propose 
merging the series? I can take the first 3 for 6.18 and then patches 4 
and 5 can go via their respective trees for 6.19?

> 
> diff --git a/drivers/of/irq.c b/drivers/of/irq.c
> index 65c3c23255b7..e67b2041e73b 100644
> --- a/drivers/of/irq.c
> +++ b/drivers/of/irq.c
> @@ -671,6 +671,35 @@ void __init of_irq_init(const struct of_device_id *matches)
>  	}
>  }
>  
> +static int of_check_msi_parent(struct device_node *dev_node, struct device_node **msi_node)
> +{
> +	struct of_phandle_args msi_spec;
> +	int ret;
> +
> +	/*
> +	 * An msi-parent phandle with a missing or == 0 #msi-cells
> +	 * property identifies a 1:1 ID translation mapping.
> +	 *
> +	 * Set the msi controller node if the firmware matches this
> +	 * condition.
> +	 */
> +	ret = of_parse_phandle_with_optional_args(dev_node, "msi-parent", "#msi-cells",
> +						  0, &msi_spec);
> +	if (!ret) {

if (ret)
	return ret;

And then save a level of indentation.

> +		if ((*msi_node && *msi_node != msi_spec.np) || msi_spec.args_count != 0)
> +			ret = -EINVAL;
> +
> +		if (!ret) {
> +			/* Return with a node reference held */
> +			*msi_node = msi_spec.np;
> +			return 0;
> +		}
> +		of_node_put(msi_spec.np);
> +	}
> +
> +	return ret;
> +}
> +
>  /**
>   * of_msi_xlate - map a MSI ID and find relevant MSI controller node
>   * @dev: device for which the mapping is to be done.
> @@ -678,7 +707,7 @@ void __init of_irq_init(const struct of_device_id *matches)
>   * @id_in: Device ID.
>   *
>   * Walk up the device hierarchy looking for devices with a "msi-map"
> - * property. If found, apply the mapping to @id_in.
> + * or "msi-parent" property. If found, apply the mapping to @id_in.
>   * If @msi_np points to a non-NULL device node pointer, only entries targeting
>   * that node will be matched; if it points to a NULL value, it will receive the
>   * device node of the first matching target phandle, with a reference held.
> @@ -692,12 +721,15 @@ u32 of_msi_xlate(struct device *dev, struct device_node **msi_np, u32 id_in)
>  
>  	/*
>  	 * Walk up the device parent links looking for one with a
> -	 * "msi-map" property.
> +	 * "msi-map" or an "msi-parent" property.
>  	 */
> -	for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent)
> +	for (parent_dev = dev; parent_dev; parent_dev = parent_dev->parent) {
>  		if (!of_map_id(parent_dev->of_node, id_in, "msi-map",
>  				"msi-map-mask", msi_np, &id_out))
>  			break;
> +		if (!of_check_msi_parent(parent_dev->of_node, msi_np))
> +			break;
> +	}
>  	return id_out;
>  }
>  
> -- 
> 2.50.1
>