linux-kernel - Re: [PATCH V3 1/3] arm64: dts: sc7180: Add wakeup support over UART RX

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Date:   Wed, 02 Sep 2020 18:39:41 +0530
From:   skakit@...eaurora.org
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        gregkh@...uxfoundation.org, Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, akashast@...eaurora.org,
        rojay@...eaurora.org, msavaliy@....qualcomm.com
Subject: Re: [PATCH V3 1/3] arm64: dts: sc7180: Add wakeup support over UART
 RX

Hi Matthias,

On 2020-08-21 21:56, Matthias Kaehlcke wrote:
> On Thu, Aug 20, 2020 at 07:21:05PM +0530, satya priya wrote:
>> Add the necessary pinctrl and interrupts to make UART
>> wakeup capable.
>> 
>> Signed-off-by: satya priya <skakit@...eaurora.org>
>> Reviewed-by: Akash Asthana <akashast@...eaurora.org>
>> ---
>> Changes in V2:
>>  - As per Matthias's comment added wakeup support for all the UARTs
>>    of SC7180.
>> 
>> Changes in V3:
>>  - No change.
>> 
>>  arch/arm64/boot/dts/qcom/sc7180.dtsi | 98 
>> ++++++++++++++++++++++++++++++------
>>  1 file changed, 84 insertions(+), 14 deletions(-)
>> 
>> diff --git a/arch/arm64/boot/dts/qcom/sc7180.dtsi 
>> b/arch/arm64/boot/dts/qcom/sc7180.dtsi
>> index d46b383..855b13e 100644
>> --- a/arch/arm64/boot/dts/qcom/sc7180.dtsi
>> +++ b/arch/arm64/boot/dts/qcom/sc7180.dtsi
>> 
>> ...
>> 
>> +			qup_uart0_sleep: qup-uart0-sleep {
>> +				pinmux {
>> +					pins = "gpio34", "gpio35",
>> +					       "gpio36", "gpio37";
>> +					function = "gpio";
> 
> What is the reason that the GPIO function needs to be selected in sleep 
> mode
> to support wakeup?
> 
> This should be explained in the commit message unless it is evident.

When QUP function is selected in sleep state, RTS/RFR is pulled high as 
soon as we enter suspend and not receiving wakeup bytes from BT SoC to 
wakeup device. Whereas in GPIO mode it is staying low and receiving 
data.

Thanks,
Satya Priya