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

Simon Glass
2018-08-20T19:29:56Z

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 :-)
> >
> > 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?

Regards,
Simon