[U-Boot] [PATCH] pci: restore initialization for DM_PCI

[Bin Meng]

Hi Simon,

On Fri, Jan 22, 2016 at 12:03 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Bin,
>
> On 21 January 2016 at 20:53, Bin Meng <bmeng.cn at gmail.com> wrote:
>> On Fri, Jan 22, 2016 at 11:36 AM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi,
>>>
>>> On 21 January 2016 at 18:39, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>> Hi Stephen,
>>>>
>>>> On Fri, Jan 22, 2016 at 7:35 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>>>> From: Stephen Warren <swarren at nvidia.com>
>>>>>
>>>>> PCI controllers should be enumerated at startup so that PCI devices
>>>>> such as Ethernet controllers are available at startup. Fix board_init_r()
>>>>> not to skip calling pci_init() when CONFIG_DM_PCI is defined, and provide
>>>>> an implementation of pci_init() for the DM case.
>>>>>
>>>>
>>>> What exact issue are you trying to fix? I posted the same question on
>>>> Simon's patch [1] before. Does your patch and Simon's fix the same
>>>> issue?
>>>>
>>>> Note I submitted a similar patch [2] last year for x86 only, to
>>>> explicitly trigger the PCI enueration. But it was not accepted.
>>>>
>>>>> Fixes: 96350f729c42 ("dm: tegra: net: Convert tegra boards to driver model
>>>>> for Ethernet")
>>>>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
>>>>> ---
>>>>> I'm not sure if relying on the side-effects of calling
>>>>> uclass_{first,ext}_device is the correct approach; is there a more explicit
>>>>> way to probe all PCI controllers?
>>>>>
>>>>> Arguably, perhaps we should introduce a "pci start" command instead of
>>>>> this change to be consistent with e.g. USB. However, that would be a
>>>>> regression relative to earlier versions of U-Boot.
>>>>> ---
>>>>
>>>> [1] http://patchwork.ozlabs.org/patch/569323/
>>>> [2] http://patchwork.ozlabs.org/patch/500246/
>>>>
>>>> Regards,
>>>> Bin
>>>
>>> This does go against the driver-model philosophy of lazy init. I
>>> wonder if we should add this patch with a Kconfig option to enable it?
>>> Then it can be enabled only for boards that need it.
>>>
>>
>> I suspect the issue is somewhere else. On Intel Galileo with a PCI
>> ethernet, it works fine without such explicit pci init. Which PCI
>> ethernet driver does not work on Tegra?
>
> It could be because that board probes PCI to get its serial to work.

Even if it does not have a PCI serial, the PCI ethernet driver should
still have a chance to get PCI bus probe by calling one of these DM
PCI APIs. See an example in eth_designware.c. That's why I'd like to
know which PCI ethernet driver is this?

>
> This could be fixed on Tegra by adding an Ethernet node to the device
> tree to cause it to be probed. But I don't think that should be a
> requirement.
>

Regards,
Bin