linux-kernel - Re: [PATCH v2 3/4] PCI/ACPI: Add Broadcom bcm2711 MCFG quirk

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Message-ID: <0f21622f-2651-d1ca-7b47-4a3060a9539c@gmail.com>
Date:   Wed, 25 Aug 2021 18:23:47 +0200
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Jeremy Linton <jeremy.linton@....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,
        sdonthineni@...dia.com, stefan.wahren@...e.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 v2 3/4] PCI/ACPI: Add Broadcom bcm2711 MCFG quirk



On 8/24/2021 11:39 PM, Jeremy Linton wrote:
> Hi,
> 
> On 8/22/21 3:53 AM, Florian Fainelli wrote:
>>
>>
>> On 8/19/2021 11:56 PM, Jeremy Linton wrote:
>>> Now that there is a bcm2711 quirk, it needs to be enabled when the
>>> MCFG is missing. Use an ACPI namespace _DSD property
>>> "linux-ecam-quirk-id" as an alternative to the MCFG OEM.
>>>
>>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>>> ---
>>>   drivers/acpi/pci_mcfg.c | 13 +++++++++++++
>>>   1 file changed, 13 insertions(+)
>>>
>>> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c
>>> index 53cab975f612..4b991ee5c66c 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 +201,18 @@ 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 may be a machine with a PCI/SMC conduit, which means it 
>>> doesn't
>>> +     * have an MCFG. Use an ACPI namespace definition instead.
>>> +     */
>>> +    if (!fwnode_property_read_string(acpi_fwnode_handle(root->device),
>>> +                     "linux-ecam-quirk-id", &soc)) {
>>> +        memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE);
>>
>> Being super paranoid here, can we use one of the "safe" string copy 
>> routines here just in case?
> 
> Hmm, I went around with this a bit when I first wrote it, because the 
> OEM fields in the ACPI tables are fixed len and don't have null 
> termination. Maybe the right thing to do here is verify the string size 
> is at least as long as the OEM_ID_SIZE and then continue to use the memcpy.

Sure, sounds entirely reasonable to me.
-- 
Florian