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

[Simon Glass]

Hi Marek,

On 18 September 2018 at 13:36, 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 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.

The compatible string is needed for the emulation driver but not for
the thing that connects to it. However as things stand you can't
attach an emulator to a bus without nesting it under the device which
it attaches to.

I suspect the best answer is to move the emulator so it is a direct
child of the bus. You would need to update sandbox_pci_get_emul() to
call device_find_first_child() on 'bus' instead of 'dev'.

Regards,
Simon