[PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver

On Tuesday, November 8, 2016 11:23:35 AM CET John Garry wrote:

On 07/11/2016 20:08, Arnd Bergmann wrote:

quoted

On Monday, November 7, 2016 2:15:10 PM CET John Garry wrote:

quoted

Hi Arnd,

The new bus type tries to model the djtag in a similar way to I2C/USB
driver arch, where we have a host bus adapter and child devices attached
to the bus. The child devices are bus driver devices and have bus
addresses. We think of the djtag as a separate bus, so we are modelling
it as such.

The bus driver offers a simple host interface for clients to read/write
to the djtag bus: bus accesses are hidden from the client, the host
drives the bus.

Ok, in that case we should probably start out by having a bus specific
DT binding, and separating the description from that of the bus master
device.

OK

quoted

I'd suggest requiring #address-cells=<1> and #size-cells=<0> in the master
node, and listing the children by reg property. If the address is not
easily expressed as a single integer, use a larger #address-cells value.

We already have something equivalent to reg in "module-id" (see patch 
02/11), which is the slave device bus address; here's a sample:
+		/* For L3 cache PMU */
+		pmul3c0 {
+			compatible = "hisilicon,hisi-pmu-l3c-v1";
+			scl-id = <0x02>;
+			num-events = <0x16>;
+			num-counters = <0x08>;
+			module-id = <0x04>;
+			num-banks = <0x04>;
+			cfgen-map = <0x02 0x04 0x01 0x08>;
+			counter-reg = <0x170>;
+			evctrl-reg = <0x04>;
+			event-en = <0x1000000>;
+			evtype-reg = <0x140>;
+		};

FYI, "module-id" is our own internal hw nomenclature.

Yes, that was my interpretation as well. Please use the standard
"reg" property for this then.

quoted

Another option that we have previously used was to actually pretend that
a vendor specific bus is an i2c bus and use the i2c probing infrastructure,
but that only makes sense if the software side closely resembles i2c
(this was the case for Allwinner I think, but I have not looked at
your driver in enough detail to know if it is true here as well).

OK, let me check this. By chance do you remember the specific AllWinner 
driver/hw?

drivers/i2c/busses/i2c-sun6i-p2wi.c

	Arnd