linux-kernel - Re: [PATCH] ata: pata_of_platform: Use of_irq_to

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Date:   Fri, 17 Dec 2021 09:23:42 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        linux-ide@...r.kernel.org
Cc:     Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>
Subject: Re: [PATCH] ata: pata_of_platform: Use of_irq_to_resource() to
 populate IRQ resource

On 12/17/21 09:12, Lad Prabhakar wrote:
> platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
> allocation of IRQ resources in DT core code, this causes an issue
> when using hierarchical interrupt domains using "interrupts" property
> in the node as this bypassed the hierarchical setup and messed up the

s/bypassed/bypasses
s/messed/messes

> irq chaining.
> 
> In preparation for removal of static setup of IRQ resource from DT core
> code use of_irq_to_resource().
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> Hi,
> 
> Dropping usage of platform_get_resource() was agreed based on
> the discussion [0].
> 
> [0] https://patchwork.kernel.org/project/linux-renesas-soc/
> patch/20211209001056.29774-1-prabhakar.mahadev-lad.rj@...renesas.com/
> 
> Cheers,
> Prabhakar
> ---
>  drivers/ata/pata_of_platform.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/pata_of_platform.c b/drivers/ata/pata_of_platform.c
> index 35aa158fc976..557f349eb533 100644
> --- a/drivers/ata/pata_of_platform.c
> +++ b/drivers/ata/pata_of_platform.c
> @@ -9,6 +9,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of_address.h>
> +#include <linux/of_irq.h>
>  #include <linux/platform_device.h>
>  #include <linux/ata_platform.h>
>  #include <linux/libata.h>
> @@ -25,11 +26,12 @@ static int pata_of_platform_probe(struct platform_device *ofdev)
>  	struct device_node *dn = ofdev->dev.of_node;
>  	struct resource io_res;
>  	struct resource ctl_res;
> -	struct resource *irq_res;
> +	struct resource irq_res;
>  	unsigned int reg_shift = 0;
>  	int pio_mode = 0;
>  	int pio_mask;
>  	bool use16bit;
> +	int irq;
>  
>  	ret = of_address_to_resource(dn, 0, &io_res);
>  	if (ret) {
> @@ -45,7 +47,9 @@ static int pata_of_platform_probe(struct platform_device *ofdev)
>  		return -EINVAL;
>  	}
>  
> -	irq_res = platform_get_resource(ofdev, IORESOURCE_IRQ, 0);
> +	irq = of_irq_to_resource(dn, 0, &irq_res);
> +	if (irq <= 0 && irq != -ENXIO)
> +		return irq ? irq : -ENXIO;

Why are you making an exception for ENXIO ? I suspect this is to cover
the case "there is no IRQ for this node", but then how does this
differentiate from a real error case ?

>  
>  	of_property_read_u32(dn, "reg-shift", &reg_shift);
>  
> @@ -63,7 +67,8 @@ static int pata_of_platform_probe(struct platform_device *ofdev)
>  	pio_mask = 1 << pio_mode;
>  	pio_mask |= (1 << pio_mode) - 1;
>  
> -	return __pata_platform_probe(&ofdev->dev, &io_res, &ctl_res, irq_res,
> +	return __pata_platform_probe(&ofdev->dev, &io_res, &ctl_res,
> +				     irq > 0 ? &irq_res : NULL,
>  				     reg_shift, pio_mask, &pata_platform_sht,
>  				     use16bit);
>  }
> 


-- 
Damien Le Moal
Western Digital Research