linux-kernel - Re: [PATCH 3/3] PCI/ACPI: Add new quirk detection, enable bcm2711

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Date:   Tue, 10 Aug 2021 09:47:12 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Shanker R Donthineni <sdonthineni@...dia.com>,
        linux-pci@...r.kernel.org
Cc:     lorenzo.pieralisi@....com, nsaenz@...nel.org, bhelgaas@...gle.com,
        rjw@...ysocki.net, lenb@...nel.org, robh@...nel.org, kw@...ux.com,
        f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] PCI/ACPI: Add new quirk detection, enable bcm2711

Hi,

Thanks for looking at this!

On 8/10/21 9:31 AM, Shanker R Donthineni wrote:
> Hi Jeremy,
> 
> On 8/5/21 4:12 PM, Jeremy Linton wrote:
>> Now that we have a bcm2711 quirk, we need to be able to
>> detect it when the MCFG is missing. Use a namespace
>> property as an alternative to the MCFG OEM.
>>
>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>> ---
>>   drivers/acpi/pci_mcfg.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
>> index 53cab975f612..7d77fc72c2a4 100644
>> --- a/drivers/acpi/pci_mcfg.c
>> +++ b/drivers/acpi/pci_mcfg.c
>> @@ -169,6 +169,9 @@ static struct mcfg_fixup mcfg_quirks[] = {
>>          ALTRA_ECAM_QUIRK(1, 13),
>>          ALTRA_ECAM_QUIRK(1, 14),
>>          ALTRA_ECAM_QUIRK(1, 15),
>> +
>> +       { "bcm2711", "", 0, 0, MCFG_BUS_ANY, &bcm2711_pcie_ops,
>> +         DEFINE_RES_MEM(0xFD500000, 0xA000) },
>>   };
>>
>>   static char mcfg_oem_id[ACPI_OEM_ID_SIZE];
>> @@ -198,8 +201,19 @@ static void pci_mcfg_apply_quirks(struct acpi_pci_root *root,
>>          u16 segment = root->segment;
>>          struct resource *bus_range = &root->secondary;
>>          struct mcfg_fixup *f;
>> +       const char *soc;
>>          int i;
>>
>> +       /*
>> +        * This could be a machine with a PCI/SMC conduit,
>> +        * which means it doens't have MCFG. Get the machineid from
>> +        * the namespace definition instead.
>> +        */
>> +       if (!fwnode_property_read_string(acpi_fwnode_handle(root->device),
>> +                                        "linux,pcie-quirk", &soc)) {
>> +               memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE);
>> +       }
>> +
> 
> Is there any specific reason for not using the firmware agnostic API to get properties?
>   
> 
>   if (!device_property_read_string(root->device, "linux,pcie-quirk", &soc)) {
>       memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE);
>   }
> 
> 

IIRC it was because the "device" here isn't a struct device, rather a 
struct acpi_device. I think this is the normal way in this situation 
since we are directly picking up the fwnode rather than finding a 
generic node and then backtracking to get the fwnode.