On Mon, Jan 12, 2015 at 06:13:41PM +0100, Jean-Francois Moine wrote:
> On Mon, 12 Jan 2015 14:04:56 +0000
> Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote:
> > On Mon, Jan 12, 2015 at 02:59:57PM +0100, Philipp Zabel wrote:
> > > Note that of_graph_parse_endpoint interprets the port node's reg
> > > property as port id. And the unit address part of the node name should
> > > match the first address in the reg property.
>
> This is not the case in vexpress-v2p-ca15_a7.dts.
Hmm... as the DT binding doc doesn't specify this restriction, and we
have a DT file which violates what Philipp has said, I think we ought
to document that reg vs unit node name does not need to match each
other, thereby making that official.
> > So that's not going to work very well... because the AP register is a
> > bitmask.
> >
> > I guess we could specify a node unit and reg, which the code otherwise
> > ignores, and specify a philipps,ap-mask = property for the audio ports
> > instead.
>
> Also, the video and audio ports must be distinguished. They could be
> defined in different port groups.
>
> Example from the Cubox:
>
> video-ports: ports@0 {
> port {
> tda998x_video: endpoint {
> remote-endpoint = <&lcd0_0>;
> nxp,video-port = <0x230145>;
> };
> };
> };
> audio-ports: ports@1 {
> port@0 { /* AP1 = I2S */
> tda998x_i2s: endpoint@0 {
> remote-endpoint = <&audio1_i2s>;
> nxp,audio-port = <0x03>;
> };
> };
> port@1 { /* AP2 = S/PDIF */
> tda998x_spdif: endpoint@1 {
> remote-endpoint = <&audio1_spdif1>;
> nxp,audio-port = <0x04>;
> };
> };
> };
>
> The port type is identified by the bit AP0.
I don't particularly like that - that makes the assumption that AP0
always means I2S. What if a future chip decides to allow SPDIF on
AP0? Why should we need to re-invent the binding?
IMHO, it would be much better to make this explicit.
Note that the "video-ports" and "audio-ports" are just labels in the
DT file; they aren't carried through to the resulting DT binary file,
so they don't have any meaning to the kernel.
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