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

Tom Rini
2018-08-15T11:25:40Z

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.

--
Tom
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