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

[Bin Meng]

Hi Marek,

On Tue, Sep 18, 2018 at 8:01 PM Marek Vasut <marek.vasut at gmail.com> wrote:
>
> 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 sandbox swap_case.c indeed supports dynamic driver binding, just
like real PCI devices. Please check doc/driver-model/pci-info.txt
(since you were modifying the same doc, I guess you missed that part
..)

> 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.

Regards,
Bin