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

Marek Vasut
2018-08-21T04:02:27Z

On 08/21/2018 05:46 AM, Bin Meng wrote:
> Hi Simon,
>
> On Tue, Aug 21, 2018 at 3:29 AM, Simon Glass <sjg@chromium.org> wrote:
>> Hi Marek,
>>
>> On 20 August 2018 at 12:42, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>
>>> 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 :-)
>>>>
>
> Yes, too long discussion :)
>
>>>> 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 ?
>>
>> We already have a compatible string as the standard way to attach
>> drivers to devices.
>>
>> For PCI, we already have PCI_DEVICE() and friends for when we can
>> attach a driver for a PCI device without using a compatible string.
>>
>> Both of these are defined in the DT specification.
>>
>> The patch seems to be a rework of PCI_DEVICE() and I cannot why it is necessary.
>>
>>>
>>>> I would like to see what Bin proposes.
>>>
>>> Me too, so far I only see "not Marek's patch" and no real alternative.
>>
>> Bin, do you have a patch you can share?
>
> No, I don't have any patch series for now, although I offered to work
> on a series to implement my proposal. I haven't started it as I wanted
> to hear your thoughts. The proposal I made is to satisfy the
> requirement that Marek insisted on. Basically Marek thought current DM
> PCI implementation is wrong to ask for a "compatible" string of a PCI
> device in the device tree, because he thought adding "compatible" to
> DT is invalid and Linux does not do that either. While I disagree we
> have to 100% follow Linux's implementation, I am still open for any
> possible design changes, if that's the preferable practice in U-Boot
> (but we have to make it clear and document this officially somewhere).
>
> The proposal I made is:
>
> * Keep pci-uclass driver's post_bind() and child_post_bind() only for
> Sandbox configuration
> * Keep the call to pci_bus_find_devfn() in pci_bind_bus_devices() only
> for Sandbox configuration
> * Sandbox is special. We should limit the mechanism of matching PCI
> emulation device via "compatible" to sandbox only

The above three points can be done separately and I don't care about
this too much.

> * Assign the DT node to the bound device in pci_find_and_bind_driver()
> if there is a valid PCI "reg" encoding for a specific PCI device in
> the device tree

This is what this patch does. And in fact, I have real hardware which
needs this patch to be useful and on which I can test if this works.

> * Create DM PCI test case against the DT node assignment
> * Remove all compatible string in U-Boot's PCI device drivers: eg:
> ehci_pci_ids[], xhci_pci_ids[], etc. IOW, all PCI device drivers
> should only use U_BOOT_PCI_DEVICE(), aka the original U-Boot option 2
> * Fork a "pci-ns16550" driver to support U_BOOT_PCI_DEVICE(), as
> currently PCI ns16550 device driver uses "compatible" string to do the
> matching, and update crownbay.dts and galileo.dts (so far I only know
> two boards are using PCI ns16550 serial port)
> * Make sure all DM PCI test cases are not broken
> * Document all of the above changes in doc/driver-model/pci-info.txt

I think you're just adding completely orthogonal stuff to this 5-liner
patch into the list and overly complicate the situation. Sure, if you
want to do all this, go ahead, but I don't see how this prevents this
particular patch from being applied , except maybe for the documentation
tweak.

--
Best regards,
Marek Vasut