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

Bin Meng
2018-08-21T03:46:19Z

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

Regards,
Bin