[U-Boot] [PATCH V2 1/2] pci: Support parsing PCI controller DT subnodes

[Marek Vasut]

On 09/14/2018 06:41 AM, Simon Glass wrote:
> Hi Marek,
> 
> On 10 September 2018 at 01:38, Marek Vasut <marek.vasut at gmail.com> wrote:
>>
>> On 09/02/2018 03:07 AM, Simon Glass wrote:
>>> Hi Marek,
>>
>> Hi,
>>
>>> On 1 September 2018 at 16:45, Marek Vasut <marek.vasut at gmail.com> wrote:
>>>>
>>>> On 09/01/2018 11:50 PM, Simon Glass wrote:
>>>>> Hi Marek,
>>>>>
>>>>> On 30 August 2018 at 07:42, Marek Vasut <marek.vasut at gmail.com> wrote:
>>>>>> On 08/30/2018 03:32 PM, Bin Meng wrote:
>>>>>>> Hi Marek,
>>>>>>>
>>>>>>> On Thu, Aug 30, 2018 at 1:07 AM Marek Vasut <marek.vasut at gmail.com> wrote:
>>>>>>>>
>>>>>>>> On 08/29/2018 05:15 PM, Bin Meng wrote:
>>>>>>>>> +Simon
>>>>>>>>>
>>>>>>>>> Hi Marek,
>>>>>>>>>
>>>>>>>>> On Wed, Aug 29, 2018 at 10:22 PM Marek Vasut <marek.vasut at gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>> On 08/24/2018 08:27 PM, Marek Vasut wrote:
>>>>>>>>>>> The PCI controller can have DT subnodes describing extra properties
>>>>>>>>>>> of particular PCI devices, ie. a PHY attached to an EHCI controller
>>>>>>>>>>> on a PCI bus. This patch parses those DT subnodes and assigns a node
>>>>>>>>>>> to the PCI device instance, so that the driver can extract details
>>>>>>>>>>> from that node and ie. configure the PHY using the PHY subsystem.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
>>>>>>>>>>> Cc: Simon Glass <sjg at chromium.org>
>>>>>>>>>>> Cc: Tom Rini <trini at konsulko.com>
>>>>>>>>>>
>>>>>>>>>> Well, bump ?
>>>>>>>>>>
>>>>>>>>>> This is the only missing patch to get my hardware working properly.
>>>>>>>>>
>>>>>>>>> I don't think we ever had an agreement on the v1 patch. Simon had a
>>>>>>>>> long email that pointed out what Linux does seems like a 'fallback' to
>>>>>>>>> find a node with no compatible string.
>>>>>>>>>
>>>>>>>>> Back to this, if we have to go with this way, please create a test
>>>>>>>>> case to cover this scenario.
>>>>>>>>
>>>>>>>> The fact that it works on a particular board is not tested enough?
>>>>>>>> Do we need a custom, special, synthetic test ?
>>>>>>>>
>>>>>>>
>>>>>>> I believe that's always been the requirement against the DM code
>>>>>>> changes. I was requested in the past when I changed something in the
>>>>>>> DM and I see other people were asked to do so. Like Alex said, it does
>>>>>>> not mean this patch was not tested enough, but to ensure future
>>>>>>> commits won't break this.
>>>>>>
>>>>>> So, do you have any suggestion how to implement this test ? It seems
>>>>>> Alex posed the same question. It doesn't seem to be trivial in the
>>>>>> context of sandbox.
>>>>>
>>>>> I suppose you need a PCI_DEVICE() declaration for sandbox, with an
>>>>> associated DT node and no compatible string. Then check that you can
>>>>> locate the device and that it read a DT property correctly.
>>>>
>>>> Is there any example of this stuff already ?
>>>
>>> See the bottom of swap_case.c. You might be able to add a new one of those,
>>>
>>> If you look at pci-controller2 in test.dts it has a device with a
>>> compatible string. You could try adding a second device with no
>>> compatible string.
>>
>> And how does that test anything ?
> 
> You can test that your code actually attaches the DT node to the
> probed device. Without you code the test would fail. Wit it, it would
> pass.

Well it won't, because the sandbox swap_case.c requires the compatible.
This all seems like a big hack to support virtual PCI devices.

The driver binds with a compatible and then pins the read/write config
reg accessors to emulate their return values. Those include PCI IDs. So
you cannot instantiate virtual PCI device without this compatible string
and thus also cannot write such a test easily.

Now I also understand where this whole discussion about compatible
strings came from though.

-- 
Best regards,
Marek Vasut