[OpenWrt-Devel] [PATCH] ramips: use gpio_hog instead of gpio-export

[Piotr Dymacz]

Hi Mathias, Birger,

On 11.08.2019 11:36, Mathias Kresin wrote:
> 02/08/2019 11:58, Birger Koblitz:
>> ramips: use gpio_hog instead of gpio-export
>> 
>> The `gpio-export` functionality is a hack for
>> missing kernel functionality, which was rejected in upstream kernel long
>> time
>> ago, for details see this email
>> http://lists.infradead.org/pipermail/openwrt-devel/2019-February/015772.html,
>> discussion in PR#1366 or
>> https://github.com/openwrt/openwrt/pull/1814#issuecomment-462942022.
>> 
>> This patch converts all remaining ramips .dts(i) files which were
>> using export-gpio and not making use of the change-direction functionality
>> to using gpio_hog instead
>> 
>> Signed-off-by: Birger Koblitz <mail at birger-koblitz.de>
>> 
>> ---
>> 
>> diff --git a/target/linux/ramips/dts/mt7620a_alfa-network_tube-e4g.dts
>> b/target/linux/ramips/dts/mt7620a_alfa-network_tube-e4g.dts
>> index 4097dc6140..ea0d9801c1 100644
>> --- a/target/linux/ramips/dts/mt7620a_alfa-network_tube-e4g.dts
>> +++ b/target/linux/ramips/dts/mt7620a_alfa-network_tube-e4g.dts
>> @@ -21,39 +21,6 @@
>>           bootargs = "console=ttyS0,115200";
>>       };
>>   
>> -    gpio-export {
>> -        compatible = "gpio-export";
>> -        #size-cells = <0>;
>> -
>> -        modem-enable {
>> -            gpio-export,name = "modem-enable";
>> -            gpio-export,output = <1>;
>> -            gpios = <&gpio1 12 GPIO_ACTIVE_HIGH>;
>> -        };
>> -
>> -        modem-rf-enable {
>> -            gpio-export,name = "modem-rf-enable";
>> -            gpio-export,output = <1>;
>> -            gpios = <&gpio0 12 GPIO_ACTIVE_HIGH>;
>> -        };
>> -
>> -        sim-select {
>> -            gpio-export,name = "sim-select";
>> -            gpio-export,output = <0>;
>> -            gpios = <&gpio0 13 GPIO_ACTIVE_HIGH>;
>> -        };
>> -
>> -        sim1-detect {
>> -            gpio-export,name = "sim1-detect";
>> -            gpios = <&gpio0 9 GPIO_ACTIVE_HIGH>;
>> -        };
>> -
>> -        sim2-detect {
>> -            gpio-export,name = "sim2-detect";
>> -            gpios = <&gpio2 1 GPIO_ACTIVE_HIGH>;
>> -        };
>> -    };
>> -
> 
> Hey Birger,
> 
> similar to my comment for the lantiq version, this doesn't work as well.
> 
> AFAIR, the Tube e4g has two sim card slots and the "sim-select" gpio is
> supposed to be used from the userspace, to select which sim card slot
> should be used.
> 
> If we hog the gpio, it can't be manipulated from the userspace anymore.
> 
> I haven't had a closer look at the patch. There might be similar issues
> for other boards.
> 
> @Piotr can confirm what I might to remember?

Yes, you're correct.

Also, the "modem-enable" should be available in user space as in case of 
some modems (without "SIM power down" feature support), only this 
approach works when changing SIM cards/slots:

put the modem in reset -> switch SIM slot -> enable modem

(still, there is a way to perform modem reset using AT command but IMHO 
it's not as convenient as toggling PERST# pin)

-- 
Cheers,
Piotr

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