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

Marek Vasut
2018-08-17T10:27:21Z

On 08/17/2018 03:51 AM, Bin Meng wrote:
> 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.

Your proposal mostly covers sandbox and that can be done separately.
My proposal is to update documentation and fix the code.

--
Best regards,
Marek Vasut