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

Marek Vasut
2018-08-20T18:42:11Z

On 08/20/2018 06:57 PM, Simon Glass wrote:
> Hi Bin,
>
> On 16 August 2018 at 19:51, Bin Meng <bmeng.cn@gmail.com> 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.
>
> This thread is too long :-)
>
> From what I understand, Marek and Bin are discussing whether a
> compatible string is needed to bind a driver.
>
> Generally it is. But with PCI and USB we have a search mechanism which
> can be used instead.
>
> The patch Marek submitted does not seems at all desirable to me.

Can you explain why ?

> I would like to see what Bin proposes.

Me too, so far I only see "not Marek's patch" and no real alternative.

--
Best regards,
Marek Vasut