[U-Boot] [PATCH] pci: Support parsing PCI controller DT subnodes

[Bin Meng <bmeng.cn@gmail.com>]

Hi Marek,

On Thu, Aug 16, 2018 at 7:47 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
> On 08/15/2018 01:25 PM, Tom Rini wrote:
>> On Wed, Aug 15, 2018 at 06:19:25PM +0800, Bin Meng wrote:
>>> Hi Marek,
>>>
>>> On Wed, Aug 15, 2018 at 5:22 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>> On 08/14/2018 11:40 AM, Bin Meng wrote:
>>>>> Hi Marek,
>>>>>
>>>>> On Tue, Aug 14, 2018 at 4:55 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>> On 08/14/2018 03:46 AM, Bin Meng wrote:
>>>>>>> Hi Marek,
>>>>>>>
>>>>>>> On Mon, Aug 13, 2018 at 9:46 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>>>> On 08/13/2018 04:24 AM, Bin Meng wrote:
>>>>>>>>> Hi Marek,
>>>>>>>>>
>>>>>>>>> On Fri, Aug 10, 2018 at 8:38 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>>>>>> On 08/10/2018 02:01 PM, Tom Rini wrote:
>>>>>>>>>>> On Wed, Aug 08, 2018 at 09:37:25PM +0200, Marek Vasut wrote:
>>>>>>>>>>>> On 08/08/2018 05:32 PM, Bin Meng wrote:
>>>>>>>>>>>>> Hi Marek,
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Wed, Aug 8, 2018 at 10:33 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>>>>>>>>>> On 08/08/2018 03:39 PM, Bin Meng wrote:
>>>>>>>>>>>>>>> Hi Marek,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Wed, Aug 8, 2018 at 9:24 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>>>>>>>>>>>>>> On 08/08/2018 03:14 PM, Bin Meng wrote:
>>>>>>>>>>>>>>>>> Hi Marek,
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Wed, Aug 8, 2018 at 9:03 PM, Marek Vasut <marek.vasut@gmail.com> 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@gmail.com>
>>>>>>>>>>>>>>>>>> Cc: Simon Glass <sjg@chromium.org>
>>>>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>>>>>  drivers/pci/pci-uclass.c | 14 ++++++++++++++
>>>>>>>>>>>>>>>>>>  1 file changed, 14 insertions(+)
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> diff --git a/drivers/pci/pci-uclass.c b/drivers/pci/pci-uclass.c
>>>>>>>>>>>>>>>>>> index 46e9c71bdf..306bea0dbf 100644
>>>>>>>>>>>>>>>>>> --- a/drivers/pci/pci-uclass.c
>>>>>>>>>>>>>>>>>> +++ b/drivers/pci/pci-uclass.c
>>>>>>>>>>>>>>>>>> @@ -662,6 +662,8 @@ static int pci_find_and_bind_driver(struct udevice *parent,
>>>>>>>>>>>>>>>>>>                 for (id = entry->match;
>>>>>>>>>>>>>>>>>>                      id->vendor || id->subvendor || id->class_mask;
>>>>>>>>>>>>>>>>>>                      id++) {
>>>>>>>>>>>>>>>>>> +                       ofnode node;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>>                         if (!pci_match_one_id(id, find_id))
>>>>>>>>>>>>>>>>>>                                 continue;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> @@ -691,6 +693,18 @@ static int pci_find_and_bind_driver(struct udevice *parent,
>>>>>>>>>>>>>>>>>>                                 goto error;
>>>>>>>>>>>>>>>>>>                         debug("%s: Match found: %s\n", __func__, drv->name);
>>>>>>>>>>>>>>>>>>                         dev->driver_data = find_id->driver_data;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +                       dev_for_each_subnode(node, parent) {
>>>>>>>>>>>>>>>>>> +                               phys_addr_t df, size;
>>>>>>>>>>>>>>>>>> +                               df = ofnode_get_addr_size(node, "reg", &size);
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +                               if (PCI_FUNC(df) == PCI_FUNC(bdf) &&
>>>>>>>>>>>>>>>>>> +                                   PCI_DEV(df) == PCI_DEV(bdf)) {
>>>>>>>>>>>>>>>>>> +                                       dev->node = node;
>>>>>>>>>>>>>>>>>> +                                       break;
>>>>>>>>>>>>>>>>>> +                               }
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> The function pci_find_and_bind_driver() is supposed to bind devices
>>>>>>>>>>>>>>>>> that are NOT in the device tree. Adding device tree access in this
>>>>>>>>>>>>>>>>> routine is quite odd. You can add the EHCI controller that need such
>>>>>>>>>>>>>>>>> PHY subnodes in the device tree and there is no need to modify
>>>>>>>>>>>>>>>>> anything I believe. If you are looking for an example, please check
>>>>>>>>>>>>>>>>> pciuart0 in arch/x86/dts/crownbay.dts.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Well this does not work for me, the EHCI PCI doesn't get a DT node
>>>>>>>>>>>>>>>> assigned, check r8a7794.dtsi for the PCI devices I use.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I think that's because you don't specify a "compatible" string for
>>>>>>>>>>>>>>> these two EHCI PCI nodes.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> That's perfectly fine, why should I specify it ? Linux has no problem
>>>>>>>>>>>>>> with it either.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> Without a "compatible" string, DM does not bind any device in the
>>>>>>>>>>>>> device tree to a driver, hence no device node created. This is not
>>>>>>>>>>>>> Linux.
>>>>>>>>>>>>
>>>>>>>>>>>> DT is NOT Linux specific, it is OS-agnostic, DT describes hardware and
>>>>>>>>>>>> hardware only. If U-Boot cannot parse DT correctly, U-Boot is broken and
>>>>>>>>>>>> must be fixed.
>>>>>>>>>>>>
>>>>>>>>>>>> This is a fix. If there is a better fix, I am open to it.
>>>>>>>>>>>
>>>>>>>>>>> DT should but isn't always OS agnostic.  DTS files that reside in the
>>>>>>>>>>> Linux Kernel are in practice is Linux-centric with the expectation that
>>>>>>>>>>> even if you could solve a given problem with valid DTS changes you make
>>>>>>>>>>> whatever is parsing it do additional logic instead.  That,
>>>>>>>>>>> approximately, is what your patch is doing.  If you added some HW
>>>>>>>>>>> description information to the dtsi file everything would work as
>>>>>>>>>>> expected as your DTS is describing the hardware and U-Boot is reading
>>>>>>>>>>> that description and figuring out what to do with it.
>>>>>>>>>>
>>>>>>>>>> Yes, you need additional logic to match the PCI controller subnode in DT
>>>>>>>>>> with PCI device BFD, that's expected. You do NOT need extra compatibles,
>>>>>>>>>> the PCI bus gives you enough information to match a driver on them. In
>>>>>>>>>> fact, adding a compatible can interfere with this matching.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Please, read U-Boot's doc/driver-model/pci-info.txt. You really don't
>>>>>>>>> understand current implementation in U-Boot. In short, U-Boot supports
>>>>>>>>> two scenarios for PCI driver binding:
>>>>>>>>
>>>>>>>> That documentation is wrong and needs to be fixed. The compatible is
>>>>>>>> optional.
>>>>>>>>
>>>>>>>
>>>>>>> No it is not wrong. The documentation reflects the update-to-date
>>>>>>> U-Boot support of PCI bus with DM.
>>>>>>
>>>>>> Which is incomplete, as it cannot parse subnodes without compatible strings.
>>>>>>
>>>>>
>>>>> No, it's by design, as I said many times. It can support parsing
>>>>> subnodes with a "compatible" string existence.
>>>>
>>>> It can support parsing subnodes with a "compatible" string existence AND
>>>> It can NOT support parsing subnodes without a "compatible" string
>>>> existence THUS It is incomplete.
>>>>
>>>>>>>>> - Declare a PCI device in the device tree. That requires specifying a
>>>>>>>>> 'compatible' string as well as 'reg' property as defined by the 'PCI
>>>>>>>>> Bus Binding' spec. DM uses the 'compatible' string to bind the driver
>>>>>>>>> for the device.
>>>>>>>>> - Don't declare a PCI device in the device tree. Instead, using
>>>>>>>>> U_BOOT_PCI_DEVICE() to declare a device and driver mapping.
>>>>>>>>>
>>>>>>>>> You can choose either two when you support PCI devices on your board,
>>>>>>>>> but you cannot mix both support together and make them a mess. In this
>>>>>>>>> patch, you hacked pci_find_and_bind_driver() which is the 2nd scenario
>>>>>>>>> to support the 1st scenario.
>>>>>>>>
>>>>>>>> Again, the DT contains all the required information to bind the node and
>>>>>>>> the driver instance. Clearly, we need option 3 for this.
>>>>>>>>
>>>>>>>
>>>>>>> Then that's a new design proposal. Anything that wants to mess up
>>>>>>> current design is a hack.
>>>>>>
>>>>>> That means every single patch anyone submits is now a hack ? Please ...
>>>>>>
>>>>>
>>>>> I never said "every single patch anyone submits is now a hack". "You
>>>>> are inserting words into my mouth and I dislike that." I said your
>>>>> current patch is against the design, and mess up current design which
>>>>> is a hack.
>>>>
>>>> But then every patch which changes the behavior is against "the design"
>>>> and thus is a hack. Ultimately, most improvements would be considered a
>>>> hack.
>>>
>>> No it depends. For this case, there are two options that DM PCI
>>> currently provides. You created a 3rd option that bring option 1 and 2
>>> together in a mixed way, yet without any documenting and additional
>>> other changes. If you posted such changes in a series and have all
>>> stuff well considered, I would not consider it a hack, but a proposed
>>> design change.
>>
>> Also, the design document is not immutable and can and should be updated
>> as needed to match changes in the code.
>
> So what is the conclusion here ? Patch the design document and apply
> this patch as is ?
>

I think we should see Simon's comments before we move forward. The
proposal I made before should come in a series, not just
documentation.

Regards,
Bin