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

Marek Vasut
2018-08-14T08:55:54Z

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.

>>> - 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 ...

>>>>> 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