On 08-10-20, 09:30, Rob Herring wrote: > On Wed, Oct 7, 2020 at 10:28 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > > + clock-names: > > + items: > > + - const: apb_pclk > > Just 'maxItems: 1' is fine here as the name is already defined. > > > + > > + arm-mhuv2-mode: > > arm,mhuv2-mode. This is what I did initially but was getting errors with it... > Needs a type reference. And this fixed it. > > + description: | > > + The MHUv2 controller may contain up to 124 channel windows (each 32-bit > > + wide). The hardware and the DT bindings allows any combination of those to > > + be used for various transport protocols. > > + > > + This property allows a platform to describe how these channel windows are > > + used in various transport protocols. The entries in this property shall be > > + present as an array of tuples, where each tuple describes details about > > + one of the transport protocol being implemented over some channel > > + window(s). > > + > > + The first field of a tuple signifies the transfer protocol, 0 is reserved > > + for doorbell protocol, 1 is reserved for single-word protocol and 2 is > > + reserved for multi-word protocol. Using any other value in the first field > > + of a tuple makes it invalid. > > + > > + The second field of a tuple signifies the number of channel windows where > > + the protocol would be used. For doorbell protocol this field signifies the > > + number of 32-bit channel windows that implement the doorbell protocol. For > > + single-word protocol this field signifies the number of 32-bit channel > > + windows that implement separate single-word protocol mailbox channels. For > > + multi-word protocol this field signifies the number of channel windows > > + used for a multi-word protocol, it should be 2 or more. > > These are based on IP configuration or a software decision? Software/firmware. The platform only fixes the total number of 32-bit registers available (channel windows) for use, how we use them is left to us. I tried to make it as generic as possible so any combinations of protocols can be used here. > > + The total number of channel windows specified here shouldn't be more than > > + the ones implemented by the platform. > > But can be less? Then do you need this to be a mask or range? Yes, we don't need to use all the windows that are available to us. I am not sure why we would need a mask/range here. Just to clarify a little, as it took me some time to come to this understanding, the maximum number of channel windows (these aren't necessarily mailbox channels) supported by the hardware is 124, i.e. 124 32-bit registers. Though a platform may implement only 8 of them, for example and the OS may want to use only 4 of them. If we use the entire thing in: - multi-word mode, we can create a single mailbox channel which is capable of transferring 124 words in one go. - single-word mode, we will end up having 124 mailbox channels, each 32 bit wide. - doorbell mode, we will end up having 124 * 32 mailbox channels. -- viresh
