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

Simon Glass
2018-08-21T18:29:51Z

Hi Marek,

On 21 August 2018 at 12:26, Marek Vasut <marek.vasut@gmail.com> wrote:
>
> 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.

So can you just add a compatible string and everything works?

Regards,
Simon