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

Marek Vasut
2018-08-16T11:47:09Z

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 ?

--
Best regards,
Marek Vasut