lkml.org 
[lkml]   [2016]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver
From
Date
On 08/11/2016 11:45, Arnd Bergmann wrote:
> On Tuesday, November 8, 2016 11:23:35 AM CET John Garry wrote:
>> On 07/11/2016 20:08, Arnd Bergmann wrote:
>>> On Monday, November 7, 2016 2:15:10 PM CET John Garry wrote:
>>>>
>>>> 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
>>
>>>
>>> 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.
>
>>> 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

Hi Arnd,

Thanks for the reference.

I think the i2c interface doesn't fully satisfy our requirements as we
need more than just a slave bus address when accessing the slave device
(which I think is what i2c uses). We also need to pass "offset" and
"mod_mask" arguments to the djtag adapter to access specific registers
in the slave device.

Cheers,
John

>
> Arnd
>
> .
>


\
 
 \ /
  Last update: 2016-11-08 14:51    [W:0.104 / U:0.304 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site