iProc bus scanning regression (after "PCI: iproc: Add PAXC interface support")

[Ray Jui]

Hi Rafal,

On 1/19/2016 11:02 PM, Rafał Miłecki wrote:
> On 20 January 2016 at 07:53, Rafał Miłecki <zajec5 at gmail.com> wrote:
>> In OpenWrt trunk code we use iProc driver for PCIe controllers on bcma
>> bus (PCIE_IPROC_BCMA). Right now we use 4.1 kernel but we backported
>> all iProc changes. Unfortunately backporting set queued for 4.5 broke
>> bus scanning on some routers.
>>
>> Most BCM4708 / BCM4709 chipsets have 3 PCIe controllers. All known
>> routers use only first 2 of them. Even if router has 3 PCIe cards, the
>> last two cards are connected to the 2nd PCIe controller.
>>
>> So that PAXC patch broke support for routers with 3 cards, 2 of them
>> at the 2nd controller. It doesn't affect routers with just 2 cards.
>> This problem was tracked down in:
>> https://dev.openwrt.org/ticket/21393
>>
>> I'm attaching two OpenWrt boot logs.
>> 1) r48381
>> It contains all backported iProc changes. The log looks "nice", but
>> only one card (0000:01:00.0) was detected.
>> 2) r48382
>> It contains "Revert "PCI: iproc: Add PAXC interface support"" patch.
>> It contains many "[Firmware Bug]: reg 0x??: invalid BAR (can't size)"
>> messages but there are all 3 cards detected: 0000:01:00.0,
>> 0001:03:00.0 and 0001:04:00.0 (see brcmfmac messages).
>>
>> Can you take a look at this problem, please?
>
> linux-arm-kernel@ stopped my e-mail due to its size. Sending
> compressed attachments.
>

I'm a bit confused by these logs that you provided. Based on the log, 
there seems to be 3 PCIe root complexes populated on the platform, 
domain 0000:00:00.0, 0001:00:00:0, 0002:00:00:0 are the 3 root 
complexes. Root complex 0002 seems to have nothing connected since it 
does not detect any EP.

Is the first card installed on root complex 0 (domain 0000), but the 
second card and 3rd card are both installed on root complex 1 (domain 
0001) on different slots or something?

I suspect a potential issue is in this function:

173 static inline bool iproc_pcie_device_is_valid(struct iproc_pcie *pcie,
174                                               unsigned int slot,
175                                               unsigned int fn)
176 {
177         if (slot > 0)
178                 return false;
179
180         /* PAXC can only support limited number of functions */
181         if (pcie->type == IPROC_PCIE_PAXC && fn >= MAX_NUM_PAXC_PF)
182                 return false;
183
184         return true;
185 }

Compared to the original code, it's different. Can you try passing bus 
number into the function as another argument and do the following check 
on line 177:

if (busnum == 0 && slot > 0)
     return false;

instead of

if (slot > 0)
     return false;

Thanks,

Ray