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

Bin Meng
2018-08-15T10:19:25Z

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.

Regards,
Bin