Hi Abdellatif, On Mon, 19 Dec 2022 at 04:12, Abdellatif El Khlifi <abdellatif.elkhl...@arm.com> wrote: > > 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.
I'm sorry I don't agree with that. It does need a compatible string, like PCI has. You can just add it in U-Boot if Linux won't accept the binding. Rob, if you are here I think the U-Boot DM bindings seem to have stalled. What is needed to get these in? Regards, Simon