linux-kernel - Re: [RFC PATCH v3 2/2] ARM64/PCI: Start using quirks handling for ACPI based PCI host controller

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Message-ID: <20160616174856.GB32388@red-moon>
Date:	Thu, 16 Jun 2016 18:48:56 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Christopher Covington <cov@...eaurora.org>
Cc:	Tomasz Nowicki <tn@...ihalf.com>, Duc Dang <dhdang@....com>,
	Dongdong Liu <liudongdong3@...wei.com>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jeff Hugo <jhugo@...eaurora.org>,
	Gabriele Paoloni <gabriele.paoloni@...wei.com>,
	Jon Masters <jcm@...hat.com>, Mark Salter <msalter@...hat.com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Jayachandran C <jchandra@...adcom.com>,
	David Daney <ddaney@...iumnetworks.com>,
	Robert Richter <robert.richter@...iumnetworks.com>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v3 2/2] ARM64/PCI: Start using quirks handling for
 ACPI based PCI host controller

On Wed, Jun 15, 2016 at 11:34:11AM -0400, Christopher Covington wrote:
> From: Tomasz Nowicki <tn@...ihalf.com>
> 
> pci_generic_ecam_ops is used by default. Since there are platforms
> which have non-compliant ECAM space we need to overwrite these
> accessors prior to PCI buses enumeration. In order to do that
> we call pci_mcfg_get_ops to retrieve pci_ecam_ops structure so that
> we can use proper PCI config space accessors and bus_shift.
> 
> pci_generic_ecam_ops is still used for platforms free from quirks.
> 
> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
> ---
>  arch/arm64/kernel/pci.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> index 94cd43c..a891bda 100644
> --- a/arch/arm64/kernel/pci.c
> +++ b/arch/arm64/kernel/pci.c
> @@ -139,6 +139,7 @@ pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root)
>  	struct pci_config_window *cfg;
>  	struct resource cfgres;
>  	unsigned int bsz;
> +	struct pci_ecam_ops *ops;
>  
>  	/* Use address from _CBA if present, otherwise lookup MCFG */
>  	if (!root->mcfg_addr)
> @@ -150,12 +151,12 @@ pci_acpi_setup_ecam_mapping(struct acpi_pci_root *root)
>  		return NULL;
>  	}
>  
> -	bsz = 1 << pci_generic_ecam_ops.bus_shift;
> +	ops = pci_mcfg_get_ops(root);
> +	bsz = 1 << ops->bus_shift;
>  	cfgres.start = root->mcfg_addr + bus_res->start * bsz;
>  	cfgres.end = cfgres.start + resource_size(bus_res) * bsz - 1;
>  	cfgres.flags = IORESOURCE_MEM;
> -	cfg = pci_ecam_create(&root->device->dev, &cfgres, bus_res,
> -			      &pci_generic_ecam_ops);
> +	cfg = pci_ecam_create(&root->device->dev, &cfgres, bus_res, ops);

Arnd pointed this out already, I think that's the only pending question
here.

pci_ecam_create() maps ECAM space for config regions retrieved from
the MCFG, which are *supposed* to be ECAM compliant.

Do we think that's *always* correct/safe regardless of the kind
of quirk we are currently fixing up ?

Or we do think that configuration space regions should come from
a different resource declared in the ACPI namespace if the regions
are not MCFG/ECAM compliant (ie config space is not defined through
MCFG at all - possibly through a _CRS method for a vendor specific
_HID under the PNP0A03 node ?)

It might even be a choice we do not have anymore, but I think it
is important to make a decision and proceed accordingly.

Comments appreciated.

Thanks,
Lorenzo

>  	if (IS_ERR(cfg)) {
>  		dev_err(&root->device->dev, "%04x:%pR error %ld mapping ECAM\n",
>  			seg, bus_res, PTR_ERR(cfg));
> -- 
> Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
>