linux-kernel - Re: [PATCH] pci: introduce static_nr to indicate domain

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Date:   Mon, 14 Aug 2023 18:11:24 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Peng Fan (OSS)" <peng.fan@....nxp.com>
cc:     bhelgaas@...gle.com, pali@...nel.org, linux-pci@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH] pci: introduce static_nr to indicate domain_nr from
 which IDA

On Sat, 12 Aug 2023, Peng Fan (OSS) wrote:

> From: Peng Fan <peng.fan@....com>
> 
> When pci node is created used an overlay, when the overlay is

pci -> PCI
created used -> created using

is created -> was created ? The current form with "is created" + "is 
reverted/destroyed" is contradictory.

Double "when" makes it hard to understand what you say. Perhaps convert 
the second when to "and".

> reverted/destroyed, the "linux,pci-domain" property is no longer
> existed

property no longer exists

>, so of_get_pci_domain_nr will return failure. Then
> of_pci_bus_release_domain_nr will actually use the dynamic IDA,
> even if the IDA was allocated in static IDA.
> 
> Introduce a static_nr field in pci_bus to indicate the IDA
> is in dynamic or static IDA to address the upper issue.

I'd say:

... to indicated whether the IDA is a dynamic or static in order to
free the correct one.

> Fixes: c14f7ccc9f5d ("PCI: Assign PCI domain IDs by ida_alloc()")
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/pci/pci.c   | 22 ++++++++++++++--------
>  include/linux/pci.h |  1 +
>  2 files changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 60230da957e0..5c98502bcda6 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6881,10 +6881,10 @@ static void of_pci_reserve_static_domain_nr(void)
>  	}
>  }
>  
> -static int of_pci_bus_find_domain_nr(struct device *parent)
> +static int of_pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
>  {
>  	static bool static_domains_reserved = false;
> -	int domain_nr;
> +	int domain_nr, ret;
>  
>  	/* On the first call scan device tree for static allocations. */
>  	if (!static_domains_reserved) {
> @@ -6892,6 +6892,8 @@ static int of_pci_bus_find_domain_nr(struct device *parent)
>  		static_domains_reserved = true;
>  	}
>  
> +	bus->static_nr = 0;
> +
>  	if (parent) {
>  		/*
>  		 * If domain is in DT, allocate it in static IDA.  This
> @@ -6899,10 +6901,14 @@ static int of_pci_bus_find_domain_nr(struct device *parent)
>  		 * in DT.
>  		 */
>  		domain_nr = of_get_pci_domain_nr(parent->of_node);
> -		if (domain_nr >= 0)
> -			return ida_alloc_range(&pci_domain_nr_static_ida,
> -					       domain_nr, domain_nr,
> -					       GFP_KERNEL);
> +		if (domain_nr >= 0) {
> +			ret = ida_alloc_range(&pci_domain_nr_static_ida,
> +					      domain_nr, domain_nr, GFP_KERNEL);
> +			if (ret >= 0)
> +				bus->static_nr = 1;
> +
> +			return ret;
> +		}
>  	}
>  
>  	/*
> @@ -6920,7 +6926,7 @@ static void of_pci_bus_release_domain_nr(struct pci_bus *bus, struct device *par
>  		return;
>  
>  	/* Release domain from IDA where it was allocated. */
> -	if (of_get_pci_domain_nr(parent->of_node) == bus->domain_nr)
> +	if (bus->static_nr)
>  		ida_free(&pci_domain_nr_static_ida, bus->domain_nr);
>  	else
>  		ida_free(&pci_domain_nr_dynamic_ida, bus->domain_nr);
> @@ -6928,7 +6934,7 @@ static void of_pci_bus_release_domain_nr(struct pci_bus *bus, struct device *par
>  
>  int pci_bus_find_domain_nr(struct pci_bus *bus, struct device *parent)
>  {
> -	return acpi_disabled ? of_pci_bus_find_domain_nr(parent) :
> +	return acpi_disabled ? of_pci_bus_find_domain_nr(bus, parent) :
>  			       acpi_pci_bus_find_domain_nr(bus);
>  }
>  
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index eeb2e6f6130f..6dd16e069ab8 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -665,6 +665,7 @@ struct pci_bus {
>  	unsigned char	cur_bus_speed;	/* enum pci_bus_speed */
>  #ifdef CONFIG_PCI_DOMAINS_GENERIC
>  	int		domain_nr;
> +	unsigned int	static_nr:1;
>  #endif
>  
>  	char		name[48];

If you put it into where the other unsigned int xx:1's are in the struct, 
it won't increase the size of the struct (but the downside is that they're 
no longer next to each other).

-- 
 i.