On Mon, Dec 05, 2022 at 09:49:30AM -0600, Rob Herring wrote: > On Sun, Dec 4, 2022 at 1:22 PM Simon Glass <s...@chromium.org> wrote: > > > > Hi Rob, > > > > On Tue, 29 Nov 2022 at 05:22, Rob Herring <r...@kernel.org> wrote: > > > > > > On Fri, Nov 25, 2022 at 3:18 PM Simon Glass <s...@chromium.org> wrote: > > > > > > > > Hi Abdellatif, > > > > > > > > On Thu, 24 Nov 2022 at 06:21, Abdellatif El Khlifi > > > > <abdellatif.elkhl...@arm.com> wrote: > > > > > > > > > > On Tue, Nov 22, 2022 at 07:09:16PM -0700, Simon Glass wrote: > > > > > > should be called 'priov' and should beHi Abdellatif, > > > > > > > > > > > > > > [..] > > > > > > > > > > > +/** > > > > > > > + * ffa_device_get - create, bind and probe the arm_ffa device > > > > > > > + * @pdev: the address of a device pointer (to be filled when the > > > > > > > arm_ffa bus device is created > > > > > > > + * successfully) > > > > > > > + * > > > > > > > + * This function makes sure the arm_ffa device is > > > > > > > + * created, bound to this driver, probed and ready to use. > > > > > > > + * Arm FF-A transport is implemented through a single U-Boot > > > > > > > + * device managing the FF-A bus (arm_ffa). > > > > > > > + * > > > > > > > + * Return: > > > > > > > + * > > > > > > > + * 0 on success. Otherwise, failure > > > > > > > + */ > > > > > > > +int ffa_device_get(struct udevice **pdev) > > > > > > > +{ > > > > > > > + int ret; > > > > > > > + struct udevice *dev = NULL; > > > > > > > + > > > > > > > + ret = device_bind(dm_root(), DM_DRIVER_GET(arm_ffa), > > > > > > > FFA_DRV_NAME, NULL, ofnode_null(), > > > > > > > + &dev); > > > > > > > > > > > > Please add a DT binding. Even if only temporary, we need something > > > > > > for this. > > > > > > > > > > Thanks for the feedback. I'm happy to address all the comments. > > > > > > > > > > Regarding DT binding and FF-A discovery. We agreed with Linaro and > > > > > Rob Herring > > > > > about the following: > > > > > > > > > > - DT is only for what we failed to make discoverable. For hardware, > > > > > we're stuck > > > > > with it. We shouldn't repeat that for software interfaces. This > > > > > approach is > > > > > already applied in the FF-A kernel driver which comes with no DT > > > > > support and > > > > > discovers the bus with bus_register() API [1]. > > > > > > > > This may be the UEFI view, but it is not how U-Boot works. This is not > > > > something we are 'stuck' with. It is how we define what is present on a > > > > device. This is how the PCI bus works in U-Boot. It is best practice in > > > > U-Boot to use the device tree to make this things visible and > > > > configurable. Unlike with Linux there is no other way to provide > > > > configuration needed by these devices. > > > > > > Where do you get UEFI out of this? > > > > I assume it was UEFI as there was no discussion about this in U-Boot. > > Which firmware project was consulted about this? > > > > > > > > It is the discoverability of hardware that is fixed (and we are stuck > > > with). We can't change hardware. The disoverability may be PCI > > > VID/PID, USB device descriptors, or nothing. We only use DT when those > > > are not sufficient. For a software interface, there is no reason to > > > make them non-discoverable as the interface can be fixed (at least for > > > new things like FF-A). > > > > Here I am talking about the controller itself, the top-level node in > > the device tree. For PCI this is a device tree node and it should be > > the same here. So I am not saying that the devices on the bus need to > > be in the device tree (that can be optional, but may be useful in some > > situations where it is status and known). > > Sure, the PCI host bridges are not discoverable, have a bunch of > resources, and do need to be in DT. The downstream devices only do if > they have extra resources such as when a device is soldered down on a > board rather than a standard slot. > > > We need something like: > > > > ff-a { > > compatible = "something"; > > }; > > > > I don't know what mechanism is actually used to communicate with it, > > but that will be enough to get the top-level driver started. > > There's discovery of FF-A itself and then discovery of FF-A features > (e.g. partitions). Both of those are discoverable without DT. The > first is done by checking the SMCCC version, then checking for FF-A > presence and features. Putting this into DT is redundant. Worse, what > if they disagree?
Hi Simon, Do you agree with Rob, Ilias and myself that it makes more sense FF-A bus is discovered without a DT node and following the same approach as Linux ? (FF-A bus doesn't have a HW controller and is a purely SW bus, no configuration/description needed at DT level). Your suggestions are always welcome. cheers > > > If Linux does not want to use the node, that it another thing, but I > > respectfully request that U-Boot's needs be considered more carefully. > > It's not really a big deal for just one compatible. It's the next 10 > firmware things Arm comes up with. Or the let's add one property at a > time binding (mis)design that happens once we have a binding. > > > I'd also like to see more willingness to accommodate open-source > > software in these designs. > > I'm not sure what you are asking for here. Are you talking about FF-A > and Arm firmware interfaces itself, the DT binding for it, or > something else? I'd agree on the first part. I only saw this when the > binding landed on my plate. For bindings themselves, the firehose is > there. I can't pick out what you or others care and don't care about. > I try to steer common things to the devicetree-spec list, but there's > not that many things that come up really. > > Rob