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

[Marek Vasut <marek.vasut@gmail.com>]

On 08/21/2018 07:32 PM, Simon Glass wrote:
> Hi Bin,
> 
> On 20 August 2018 at 21:46, Bin Meng <bmeng.cn@gmail.com> 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
>> * 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
>> * 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
>>
> 
> Thanks very much for all the info. But I don't understand why we want
> to remove compatible strings? They are part of the DT specification.

Unrelated orthogonal cleanup / optimization IMO.

-- 
Best regards,
Marek Vasut