linux-kernel - Re: [PATCH v2 2/4] PCI: cadence: Use "dma-ranges" instead of "cdns,no-bar-match-nbits" property

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Message-ID: <dc581c5b-11de-f4b3-e928-208b9293e391@arm.com>
Date:   Fri, 1 May 2020 16:54:17 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Kishon Vijay Abraham I <kishon@...com>
Cc:     Tom Joseph <tjoseph@...ence.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Andrew Murray <amurray@...goodpenguin.co.uk>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] PCI: cadence: Use "dma-ranges" instead of
 "cdns,no-bar-match-nbits" property

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@...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?

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.

Robin.

>> +
>> +	if (!rc->no_bar_nbits) {
>> +		rc->no_bar_nbits = 32;
>> +		of_property_read_u32(np, "cdns,no-bar-match-nbits",
>> +				     &rc->no_bar_nbits);
>> +	}
>>   
>>   	rc->vendor_id = 0xffff;
>>   	of_property_read_u16(np, "vendor-id", &rc->vendor_id);
>> -- 
>> 2.17.1
>>