linux-kernel - Re: [PATCH v2] of: property: Add fw_devlink support for interrupt-map property

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Message-ID: <20240416141049.GA2148267-robh@kernel.org>
Date: Tue, 16 Apr 2024 09:10:49 -0500
From: Rob Herring <robh@...nel.org>
To: Anup Patel <apatel@...tanamicro.com>
Cc: Saravana Kannan <saravanak@...gle.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Atish Patra <atishp@...shpatra.org>,
	Andrew Jones <ajones@...tanamicro.com>,
	Sunil V L <sunilvl@...tanamicro.com>,
	Anup Patel <anup@...infault.org>, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2] of: property: Add fw_devlink support for
 interrupt-map property

On Sat, Apr 13, 2024 at 02:49:42PM +0530, Anup Patel wrote:
> Some of the PCI controllers (such as generic PCI host controller)
> use "interrupt-map" DT property to describe the mapping between
> PCI endpoints and PCI interrupt pins. This the only case where
> the interrupts are not described in DT.
> 
> Currently, there is no fw_devlink created based on "interrupt-map"
> DT property so interrupt controller is not guaranteed to be probed
> before PCI host controller. This affects every platform where both
> PCI host controller and interrupt controllers are probed as regular
> platform devices.
> 
> This creates fw_devlink between consumers (PCI host controller) and
> supplier (interrupt controller) based on "interrupt-map" DT property.
> 
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
> Changes since v1:
> - Updated commit description based on Rob's suggestion
> - Use of_irq_parse_raw() for parsing interrupt-map DT property
> ---
>  drivers/of/property.c | 58 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index a6358ee99b74..67be66384dac 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1311,6 +1311,63 @@ static struct device_node *parse_interrupts(struct device_node *np,
>  	return of_irq_parse_one(np, index, &sup_args) ? NULL : sup_args.np;
>  }
>  
> +static struct device_node *parse_interrupt_map(struct device_node *np,
> +					       const char *prop_name, int index)
> +{
> +	const __be32 *imap, *imap_end, *addr;
> +	struct of_phandle_args sup_args;
> +	struct device_node *tn, *ipar;
> +	u32 addrcells, intcells;
> +	int i, j, imaplen;
> +
> +	if (!IS_ENABLED(CONFIG_OF_IRQ))
> +		return NULL;
> +
> +	if (strcmp(prop_name, "interrupt-map"))
> +		return NULL;
> +
> +	ipar = of_node_get(np);
> +	do {
> +		if (!of_property_read_u32(ipar, "#interrupt-cells", &intcells))
> +			break;
> +		tn = ipar;
> +		ipar = of_irq_find_parent(ipar);
> +		of_node_put(tn);
> +	} while (ipar);

No need for this loop. We've only gotten here if 'interrupt-map' is 
present in the node and '#interrupt-cells' is required if 
'interrupt-map' is present.

> +	if (!ipar)
> +		return NULL;
> +	addrcells = of_bus_n_addr_cells(ipar);
> +	of_node_put(ipar);
> +
> +	imap = of_get_property(np, "interrupt-map", &imaplen);
> +	if (!imap || imaplen <= (addrcells + intcells))
> +		return NULL;
> +	imap_end = imap + imaplen;
> +
> +	sup_args.np = NULL;
> +	for (i = 0; i <= index && imap < imap_end; i++) {
> +		if (sup_args.np) {
> +			of_node_put(sup_args.np);
> +			sup_args.np = NULL;
> +		}
> +
> +		addr = imap;
> +		imap += addrcells;
> +
> +		sup_args.np = np;
> +		sup_args.args_count = intcells;
> +		for (j = 0; j < intcells; j++)
> +			sup_args.args[j] = be32_to_cpu(imap[j]);
> +		imap += intcells;
> +
> +		if (of_irq_parse_raw(addr, &sup_args))
> +			return NULL;
> +		imap += sup_args.args_count + 1;
> +	}

Doesn't this leak a ref on the last time the function is invoked? For 
example, if we have 2 entries and index is 2. We'll get index=1, but 
then exit because imap==imap_end. We need a put on index==1 node.

Look at my next branch where I've converted things to use __free() 
cleanups. I don't see it helping here as-is, but maybe when it is 
correct.

Rob