On Thu, Jan 19, 2023 at 10:21:07AM -0700, Simon Glass wrote: > Hi Tom, > > On Thu, 19 Jan 2023 at 09:57, Tom Rini wrote: > > > > On Thu, Jan 19, 2023 at 09:54:29AM -0700, Simon Glass wrote: > > > Hi Sudeep, > > > > > > On Thu, 19 Jan 2023 at 09:46, Sudeep Holla wrote: > > > > > > > > Hi Abdellatif, > > > > > > > > On Thu, Jan 19, 2023 at 04:31:57PM +0000, Abdellatif El Khlifi wrote: > > > > > > > > > > Hi Simon, Tom, > > > > > > > > > > The FF-A transport is a SW bus and is not associated to any HW peripheral or > > > > > undiscoverable base address. > > > > > > > > > > There is only 1 way of discovering the FF-A bus and it's through the FF-A SW > > > > > interfaces. The FF-A spec [1] describes this in details. > > > > > > > > > > Discovering means gathering information about the FF-A framework such as: > > > > > the FF-A version, supported features, secure partitions number and attributes. > > > > > > > > > > Please refer to the following paragraphs for more details: [2], [3], [4], [5] > > > > > > > > > > The core driver provided by this patchset implements the Setup and discovery interfaces > > > > > in addition to direct messaging. > > > > > > > > > > The driver provides ffa_bus_discover() API that allows to discover the FF-A bus > > > > > as described by the spec and in the FF-A driver readme [6]. > > > > > > > > > > We expect and highly recommend FF-A users to always discover the FF-A bus using ffa_bus_discover() API. > > > > > > > > > > > > > Thanks for the details. But IIRC this discussion is not about the FF-A bus > > > > and device(partitions) discovery, but the support for FF-A itself. The > > > > discussion is about where to have a device node to represent the existence of > > > > FF-A support on a platform. If we are talking about individual partitions > > > > (devices) in the device tree, then that is pure stupidity as it goes out > > > > of since with the firmware the moment a partition is added or removed in > > > > the firmware. > > > > > > > > IIUC, the whole discussion was around whether to use FFA_VERSION as the > > > > discovery mechanism for existence of FF-A support on a platform or you > > > > have a device node to specify the same. > > > > > > No, with respect, that is not quite the situation here. > > > > > > > > > > > Just to be clear, even if it is decided to add a device node, the > > > > FFA_VERSION must be used to detect the presence of FF-A support and > > > > return error otherwise. DT node presence is just to satisfy the design > > > > and must be treated as no auto-confirmation for the presence of FF-A > > > > support. We are just arguing the device node presence is just redundant, > > > > but as mentioned before it is up to U-Boot community to make a call on > > > > what is best. > > > > > > U-Boot driver model design already supports this. You can have a > > > device that binds (from DT) but will not probe because it is not > > > present / wrong version. Perhaps this was missed in the conversion to > > > Linux: > > > > > > https://u-boot.readthedocs.io/en/latest/develop/driver-model/design.html#driver-lifecycle > > > > > > So there is nothing clever needed here at all and anything you do just > > > adds confusion and bad precedent. > > > > But it's also true that at run-time, within U-Boot, we can modify the > > device tree we have, with live tree yes? So, the whole series in > > question here can be done without modifying the base DT and getting in > > to the further discussions that doing so entails. The assertion is that > > the software discoverable bus here is sufficient to not need DT, so, OK, > > lets go. > > One of the reasons that I find this all so frustrating is that it is > circular logic: > > 1. Device-tree bindings are controlled by Linux; U-Boot cannot upstream bindings > 2. We can only have upstreamed bindings in any device tree > > We have invented a whole u-boot.dtsi feature in U-Boot to hold > modifications from Linux. Board vendors have been suffering with this > for years. > > It is not fair and it really needs to stop. I am doing what I can to > upstream some basic U-Boot bindings and I hope that will work and can > lead to a healthier relationship here. Yes, but this is a problem outside of that scope. The argument here is that one does not need a device tree node to work. So lets see just how clean and nice the code can be without what you and I have been insisting would lead to the cleanest result. -- Tom