linux-kernel - Re: [PATCH v4 1/8] dt-bindings: serial: describe SA8255p

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Message-ID: <8ed44a58-eed3-4be6-9c63-7c6c172a6b7f@kernel.org>
Date: Tue, 6 May 2025 08:15:10 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Praveen Talari <quic_ptalari@...cinc.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
 devicetree@...r.kernel.org, psodagud@...cinc.com, djaggi@...cinc.com,
 quic_msavaliy@...cinc.com, quic_vtanuku@...cinc.com,
 quic_arandive@...cinc.com, quic_mnaresh@...cinc.com,
 quic_shazhuss@...cinc.com, Nikunj Kela <quic_nkela@...cinc.com>
Subject: Re: [PATCH v4 1/8] dt-bindings: serial: describe SA8255p

On 05/05/2025 15:42, Praveen Talari wrote:
> Hi Krzysztof
> 
> On 5/5/2025 3:29 PM, Krzysztof Kozlowski wrote:
>> On 05/05/2025 08:51, Praveen Talari wrote:
>>>>>>> +    serial@...000 {
>>>>>>> +        compatible = "qcom,sa8255p-geni-uart";
>>>>>>> +        reg = <0x990000 0x4000>;
>>>>>>> +        interrupts = <GIC_SPI 531 IRQ_TYPE_LEVEL_HIGH>;
>>>>>> Why isn't here wakeup interrupt? Commit msg also does not help me to
>>>>>> understand why number of interrupts varies.
>>>>> Currently we are not using wake-irq because it is optional for our current
>>>>> implementation.
>>>> Great explanation. I asked why is it optional, answer because it is
>>>> optional.
>>> sorry.
>>>> What does it mean optional? This is part of the SoC, so how given one,
>>>> fixed SoC can have it routed or not routed in the same time?
>>> the serial driver doesn't enter runtime suspend mode until the port is
>>> closed.
>>>
>>> therefore, there is no need for a wake IRQ when the driver is in an
>>> active state
>> You described current Linux driver, so if we change Linux driver or we
>> try for example FreeBSD, then bindings are different?
> 
> Currently, the driver includes code to register the device's wakeup 
> capability
> 
> but it lacks the necessary handler code for wakeup IRQ. According to the 
> serial driver,
> 
> the wake IRQ is meant to wake up the device but the device remains 
> active because
> 
> the serial driver does not enter runtime suspend mode until the port 
> closed.
> 
> So it is better to exclude the wake IRQ until the appropriate code is added.
But my driver on FreeBSD handles the wake IRQ, why you cannot add the
IRQ for it?

Best regards,
Krzysztof