Re: [PATCH 2/2] PCI: iproc: add bcma pcie driver

[Ray Jui <rjui@broadcom.com>]

Hi Rafal,

On 5/13/2015 9:19 AM, Rafał Miłecki wrote:
> On 13 May 2015 at 17:56, Ray Jui <rjui@broadcom.com> wrote:
>> On 5/12/2015 11:27 PM, Rafał Miłecki wrote:
>>> On 12 May 2015 at 23:23, Hauke Mehrtens <hauke@hauke-m.de> wrote:
>>>> This driver adds support for the PCIe 2.0 controller found on the bcma
>>>> bus. This controller can be found on (mostly) all Broadcom BCM470X /
>>>> BCM5301X ARM SoCs.
>>>>
>>>> The driver found in the Broadcom SDK does some more stuff, like setting
>>>> up some DMA memory areas, chaining MPS and MRRS to 512 and also some
>>>> PHY changes like "improving" the PCIe jitter and doing some special
>>>> initializations for the 3rd PCIe port.
>>>>
>>>> This was tested on a bcm4708 board with 2 PCIe ports and wireless cards
>>>> connected to them.
>>>>
>>>> PCI_DOMAINS is needed by this driver, because normally there is more
>>>> than one PCIe controller and without PCI_DOMAINS only the first
>>>> controller gets registered.
>>>> This controller gets 6 IRQs, the last one is trigged by all IRQ events.
>>>>
>>>> Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
>>>
>>> Acked-by: Rafał Miłecki <zajec5@gmail.com>
>>>
>>>
>>>> +static int iproc_pcie_bcma_probe(struct bcma_device *bdev)
>>>> +{
>>>> +       struct iproc_pcie *pcie;
>>>> +       LIST_HEAD(res);
>>>> +       struct resource res_mem;
>>>> +       int ret;
>>>> +
>>>> +       pcie = devm_kzalloc(&bdev->dev, sizeof(*pcie), GFP_KERNEL);
>>>> +       if (!pcie)
>>>> +               return -ENOMEM;
>>>> +
>>>> +       pcie->dev = &bdev->dev;
>>>> +       bcma_set_drvdata(bdev, pcie);
>>>> +
>>>> +       pcie->base = bdev->io_addr;
>>>> +
>>>> +       res_mem.start = bdev->addr_s[0];
>>>> +       res_mem.end = bdev->addr_s[0] + SZ_128M - 1;
>>>> +       res_mem.name = "PCIe MEM space";
>>>> +       res_mem.flags = IORESOURCE_MEM;
>>>> +       pci_add_resource(&res, &res_mem);
>>>> +
>>>> +       pcie->resources = &res;
>>>> +
>>>> +       pcie->map_irq = iproc_pcie_bcma_map_irq;
>>>> +
>>>> +       ret = iproc_pcie_setup(pcie);
>>>
>>> I think I don't like this part of iproc design. It lefts
>>> pcie->resources pointing to some random memory after the setup/probe
>>> are done. Guess it should be a separated parameter or sth.
>>>
>>> The patch is still OK, I just refer to generic iproc possible issue.
>>>
>> Sorry Rafal, but could you please be more specific on this?
> 
> iproc_pcie_pltfm_probe (and iproc_pcie_bcma_probe) have local "res"
> variable (each its own). They do:
> pcie->resources = &res;
> and then they call
> iproc_pcie_setup(pcie);
> 
> After iproc_pcie_pltfm_probe / iproc_pcie_bcma_probe returns, the
> pointer pcie->resources is not valid anymore, yet pcie struct is still
> in use. Of course pcie->resources isn't used anymore, but still, it's
> some in-struct pointer (to the random memory since local variable is
> not accessible anymore).
> 
> I think you should drop
> struct list_head *resources;
> from the struct iproc_pcie and use
> iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *resources)
> 

Okay thanks. That makes sense.

Or I should keep a copy of the resources under pcie->resources. In the
current pcie-iproc.c, the resource is not used anywhere else except when
creating the root bus under iproc_pcie_setup. But in the future, I might
need to add more code to explicitly program the outbound/inbound windows
so this driver can work with some other iProc SoCs where the desired
windows do not match power-on-reset values.

I plan to change this along with the window programming patch in the
future. I also think Hauke's current patch is fine.

Thanks,

Ray