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

Marek Vasut
2018-08-13T13:46:25Z

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.

> - 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.

>>> The problem here is that in Linux, something that sees the compatible
>>> renesas,pci-r8a7794 or renesas,pci-rcar-gen2 is doing whatever else
>>> needs to be done. Or something else? Please explain how what you want
>>> to have work here in U-Boot is working in the Linux kernel. Thanks!
>>
>> This has nothing to do with a specific controller. iMX6 does the same
>> thing, see ie arch/arm/boot/dts/imx6q-utilite-pro.dts .
>>
>
> Regards,
> Bin
>

--
Best regards,
Marek Vasut