linux-kernel - Re: [PATCH V3 13/21] pci, acpi: Provide generic way to assign bus domain number.

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Date:	Thu, 21 Jan 2016 19:38:51 +0100
From:	Tomasz Nowicki <tn@...ihalf.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	bhelgaas@...gle.com, arnd@...db.de, will.deacon@....com,
	catalin.marinas@....com, rjw@...ysocki.net, hanjun.guo@...aro.org,
	okaya@...eaurora.org, jiang.liu@...ux.intel.com,
	Stefano.Stabellini@...citrix.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com, tglx@...utronix.de,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	jchandra@...adcom.com, jcm@...hat.com
Subject: Re: [PATCH V3 13/21] pci, acpi: Provide generic way to assign bus
 domain number.

On 21.01.2016 19:22, Lorenzo Pieralisi wrote:
> Hi Tomasz,
>
> On Wed, Jan 13, 2016 at 02:20:59PM +0100, Tomasz Nowicki wrote:
>
> [...]
>
>> @@ -4796,14 +4797,34 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
>>   	 * API and update the use_dt_domains value to keep track of method we
>>   	 * are using to assign domain numbers (use_dt_domains = 0).
>>   	 *
>> +	 * IF ACPI, we expect non-DT method (use_dt_domains == -1)
>> +	 * and call _SEG method for corresponding host bridge device.
>> +	 * If _SEG method does not exist, following ACPI spec (6.5.6)
>> +	 * all PCI buses belong to domain 0.
>> +	 *
>>   	 * All other combinations imply we have a platform that is trying
>> -	 * to mix domain numbers obtained from DT and pci_get_new_domain_nr(),
>> -	 * which is a recipe for domain mishandling and it is prevented by
>> -	 * invalidating the domain value (domain = -1) and printing a
>> -	 * corresponding error.
>> +	 * to mix domain numbers obtained from DT, ACPI and
>> +	 * pci_get_new_domain_nr(), which is a recipe for domain mishandling and
>> +	 * it is prevented by invalidating the domain value (domain = -1) and
>> +	 * printing a corresponding error.
>>   	 */
>> +
>>   	if (domain >= 0 && use_dt_domains) {
>>   		use_dt_domains = 1;
>> +#ifdef CONFIG_ACPI
>> +	} else if (!acpi_disabled && use_dt_domains == -1) {
>> +		struct acpi_device *acpi_dev = to_acpi_device(parent);
>> +		unsigned long long segment = 0;
>> +		acpi_status status;
>> +
>> +		status = acpi_evaluate_integer(acpi_dev->handle,
>> +					       METHOD_NAME__SEG, NULL,
>> +					       &segment);
>> +		if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
>> +			dev_err(&acpi_dev->dev,  "can't evaluate _SEG\n");
>> +
>> +		domain = segment;
>> +#endif
>
> I think you can reshuffle a bit the code to make it easier to follow.
>
> How about this ? (on top of mainline, I just compiled it do not
> take it verbatim):
>
> -- >8 --
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index d1a7105..467a316 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -7,6 +7,7 @@
>    *	Copyright 1997 -- 2000 Martin Mares <mj@....cz>
>    */
>
> +#include <linux/acpi.h>
>   #include <linux/kernel.h>
>   #include <linux/delay.h>
>   #include <linux/init.h>
> @@ -4769,7 +4770,27 @@ int pci_get_new_domain_nr(void)
>   }
>
>   #ifdef CONFIG_PCI_DOMAINS_GENERIC
> -void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> +/* Feel free to add this to drivers/acpi as a helper */
> +#ifdef CONFIG_ACPI
> +int pci_bus_acpi_domain_nr(struct device *parent)
> +{
> +	struct acpi_device *acpi_dev = to_acpi_device(parent);
> +	unsigned long long segment = 0;
> +	acpi_status status;
> +
> +	status = acpi_evaluate_integer(acpi_dev->handle,
> +				       METHOD_NAME__SEG, NULL,
> +				       &segment);
> +	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
> +		dev_err(&acpi_dev->dev,  "can't evaluate _SEG\n");
> +
> +	return segment;
> +}
> +#else
> +int pci_bus_acpi_domain_nr(struct device *parent) { return -1; }
> +#endif
> +
> +int pci_bus_of_domain_nr(struct device *parent)
>   {
>   	static int use_dt_domains = -1;
>   	int domain = of_get_pci_domain_nr(parent->of_node);
> @@ -4811,7 +4832,13 @@ void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
>   		domain = -1;
>   	}
>
> -	bus->domain_nr = domain;
> +	return domain;
> +}
> +
> +void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> +{
> +	bus->domain_nr = acpi_disabled ? pci_bus_of_domain_nr(parent) :
> +					 pci_bus_acpi_domain_nr(parent);
>   }
>   #endif
>   #endif
>

It looks nice, I will integrate your patch. Thanks!

Tomasz