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

Simon Glass
2018-08-21T17:32:02Z

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.

Regards,
Simon