Messages in this thread | | | Subject | Re: [PATCH v2 2/4] PCI: cadence: Use "dma-ranges" instead of "cdns,no-bar-match-nbits" property | From | Robin Murphy <> | Date | Mon, 4 May 2020 11:54:24 +0100 |
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On 2020-05-04 9:44 am, Kishon Vijay Abraham I wrote: > Hi Robin, > > On 5/1/2020 9:24 PM, Robin Murphy wrote: >> On 2020-05-01 3:46 pm, Lorenzo Pieralisi wrote: >>> [+Robin - to check on dma-ranges intepretation] >>> >>> I would need RobH and Robin to review this. >>> >>> Also, An ACK from Tom is required - for the whole series. >>> >>> On Fri, Apr 17, 2020 at 05:13:20PM +0530, Kishon Vijay Abraham I wrote: >>>> Cadence PCIe core driver (host mode) uses "cdns,no-bar-match-nbits" >>>> property to configure the number of bits passed through from PCIe >>>> address to internal address in Inbound Address Translation register. >>>> >>>> However standard PCI dt-binding already defines "dma-ranges" to >>>> describe the address range accessible by PCIe controller. Parse >>>> "dma-ranges" property to configure the number of bits passed >>>> through from PCIe address to internal address in Inbound Address >>>> Translation register. >>>> >>>> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com> >>>> --- >>>> drivers/pci/controller/cadence/pcie-cadence-host.c | 13 +++++++++++-- >>>> 1 file changed, 11 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c >>>> b/drivers/pci/controller/cadence/pcie-cadence-host.c >>>> index 9b1c3966414b..60f912a657b9 100644 >>>> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c >>>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c >>>> @@ -206,8 +206,10 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc) >>>> struct device *dev = rc->pcie.dev; >>>> struct platform_device *pdev = to_platform_device(dev); >>>> struct device_node *np = dev->of_node; >>>> + struct of_pci_range_parser parser; >>>> struct pci_host_bridge *bridge; >>>> struct list_head resources; >>>> + struct of_pci_range range; >>>> struct cdns_pcie *pcie; >>>> struct resource *res; >>>> int ret; >>>> @@ -222,8 +224,15 @@ int cdns_pcie_host_setup(struct cdns_pcie_rc *rc) >>>> rc->max_regions = 32; >>>> of_property_read_u32(np, "cdns,max-outbound-regions", &rc->max_regions); >>>> - rc->no_bar_nbits = 32; >>>> - of_property_read_u32(np, "cdns,no-bar-match-nbits", &rc->no_bar_nbits); >>>> + if (!of_pci_dma_range_parser_init(&parser, np)) >>>> + if (of_pci_range_parser_one(&parser, &range)) >>>> + rc->no_bar_nbits = ilog2(range.size); >> >> You probably want "range.pci_addr + range.size" here just in case the bottom of >> the window is ever non-zero. Is there definitely only ever a single inbound >> window to consider? > > Cadence IP has 3 inbound address translation registers, however we use only 1 > inbound address translation register to map the entire 32 bit or 64 bit address > region.
OK, if anything that further strengthens the argument for deprecating a single "number of bits" property in favour of ranges that accurately describe the window(s). However it also suggests that other users in future might have some expectation that specifying "dma-ranges" with up to 3 entries should work to allow a more restrictive inbound configuration. Thus it would be desirable to make the code a little more robust here - even if we don't support multiple windows straight off, it would still be better to implement it in a way that can be cleanly extended later, and at least say something if more ranges are specified rather than just silently ignoring them.
>> I believe that pci_parse_request_of_pci_ranges() could do the actual parsing >> for you, but I suppose plumbing that in plus processing the resulting >> dma_ranges resource probably ends up a bit messier than the concise open-coding >> here. > > right, pci_parse_request_of_pci_ranges() parses "ranges" property and is used > for outbound configuration, whereas here we parse "dma-ranges" property and is > used for inbound configuration.
If you give it a valid third argument it *also* parses "dma-ranges" into a list of inbound regions. This is already used by various other drivers for equivalent inbound window setup, which is what I was hinting at before, but given the extensibility argument above I'm now going to actively suggest following that pattern for consistency.
Robin.
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