Messages in this thread | | | Subject | Re: [RFC PATCH v3 2/2] ARM64/PCI: Start using quirks handling for ACPI based PCI host controller | From | Christopher Covington <> | Date | Mon, 20 Jun 2016 13:17:33 -0400 |
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Hi Duc,
On 06/20/2016 05:42 AM, Lorenzo Pieralisi wrote: > On Fri, Jun 17, 2016 at 02:37:02PM -0700, Duc Dang wrote: >> On Thu, Jun 16, 2016 at 10:48 AM, Lorenzo Pieralisi >> <lorenzo.pieralisi@arm.com> wrote: >>> On Wed, Jun 15, 2016 at 11:34:11AM -0400, Christopher Covington wrote: >>>> From: Tomasz Nowicki <tn@semihalf.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@semihalf.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 ?) >> >> Hi Lorenzo, >> >> For X-Gene: the ECAM space is used to access the configuration space >> of PCIe devices, with additional help from controller register to >> specify the bus, device and function number. Below is the RFC patch >> that implements ECAM fixup for X-Gene PCIe controller on top of this >> RFC ECAM quirk v3 for your and others reference. > > Yes, you have an additional resource in the PNP0A03 _CRS to describe > your register that is a deliberate abuse of the ACPI standard in > that the _CRS is meant to describe resources that are passed on > to secondary buses
A potential alternative came up in an off-list discussion: Would it be better to hard code the information in the quirk workaround than look it up from a repurposed ACPI resource?
Supporting quirk workarounds for early, non-compliant hardware is helpful and perhaps necessary for bootstrapping the ecosystem in a timely manner. But we don't really want to provide an expandable or reusable interface that would make it easy for new hardware to remain non-compliant.
Regards, Cov
-- Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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