Re: [RFC] SW connection between DVB Transport Stream demuxer and I2C-based frontend

[Marc Gonzalez <marc.w.gonzalez@xxxxxxx>]

On 08/07/2019 21:58, Peter Rosin wrote:

> On 2019-07-08 13:08, Marc Gonzalez wrote:
> 
>> PROBLEM #2
>>
>> The tuner (si2157) is not on the i2c5 bus, instead it is on a private
>> i2c bus *behind* si2168, which routes requests to the proper client.
>> For the time being, I don't know how to model this relationship in DT.
>> (TODO: check i2c_slave_cb_t slave_cb in struct i2c_client)
>> I have initialized si2157 in the si2168 driver, but this doesn't feel
>> right. (Though it seems all(?) users pair 2168 with 2157.)
>>
>>
>> diff --git a/arch/arm64/boot/dts/qcom/apq8098-batfish.dts b/arch/arm64/boot/dts/qcom/apq8098-batfish.dts
>> index 29d59ecad138..9353e62375a7 100644
>> --- a/arch/arm64/boot/dts/qcom/apq8098-batfish.dts
>> +++ b/arch/arm64/boot/dts/qcom/apq8098-batfish.dts
>> @@ -30,6 +30,28 @@
>>  	status = "ok";
>>  };
>>  
>> +&blsp1_i2c5 {
>> +	status = "ok";
>> +	clock-frequency = <100000>;
>> +	pinctrl-names = "default";
>> +	pinctrl-0 = <&i2c5_default>;
>> +
>> +	dvb_demod: si2168@64 {
>> +		compatible = "silabs,si2168";
>> +		reg = <0x64>;
>> +		reset-gpios = <&tlmm 84 GPIO_ACTIVE_LOW>;
> 
> 
> In principle, I think you should be able to add something like this here:
> 
> 		i2c-gate {
> 			#address-cells = <1>;
> 			#size-cells = <0>;
> 
> 			tuner@60 {
> 				compatible = "silabs,si2157";
> 				reg = <0x60>;
> 				/* whatever else is needed */
> 			};
> 		};
> 
> But in practice, I don't know if the si2157 driver understands that or
> if there is anything else that gets in the way. Totally untested...
> 
> The i2c-gate child node is examined when you call i2c_mux_add_adapter
> if you have provided the correct struct device in the second argument
> when you called i2c_mux_alloc (I think that is already the case). You
> also need to set the I2C_MUX_GATE flag in the i2c_mux_alloc call, but
> I do not see a problem with that since I think only one child adapter
> is added. If it is a problem to add the I2C_MUX_GATE flag, then you
> can just adjust the above i2c-gate node according to the bindings in
> Documentation/devicetree/bindings/i2c/i2c-mux.txt. I.e. add this
> instead of the above i2c-gate node:
> 
> 		i2c-mux {
> 			#address-cells = <1>;
> 			#size-cells = <0>;
> 
> 			i2c@0 {
> 	                        #address-cells = <1>;
>         	                #size-cells = <0>;
>                 	        reg = <0>;
> 
> 				tuner@60 {
> 					compatible = "silabs,si2157";
> 					reg = <0x60>;
> 					/* whatever else is needed */
> 				};
> 			};
> 		};
> 
> But it feels *right* to add the I2C_MUX_GATE flag, because a gate is
> what you have. I think?

Thanks, Peter!

Your solution works great. It's refreshing to have stuff work
out-of-the-box!

Problem #2 is now taken care of. And Brad proposed an elegant
solution (IMO) for Problem #1.

I'll send an updated RFC v2 tomorrow. (My patch series is a
complete mess right now.)

Regards.